| Author | Message | |||
     KC Saayman Unregistered guest Posted From: 168.209.98.67 |
My Mk VI (B 108 CF), which used to run very cool, has suddenly started overheating. The water temperature seems to rise especially on the open road, at higher speeds, and then starts boiling. I flushed the engine and radiator earlier today, and have the following questions. 1) The thermostat is not original. It has been replaced with a modern, of the shelf thermostat. Is this acceptable? Will water still flow down the by-pass before the thermostat opens? 2) I opened the cylinder block drain tap, but could not get more than a few drops of water out of there. This seems to indicate a blockage? Should I remove the drain tap from the cylinder block and try flushing from there to clear the blockage? (Water flowed freely from the heater tap on the opposite side of the cylinder block) 3) Is it safe to drive the car for short distances without a thermostat while I wait for advice, and possibly for a new thermostat from the UK? I’d appreciate your advice. Kind regards KC (Message approved by david_gore) | |||
| Bill Vatter New User Username: bill_vatter Post Number: 4 Registered: 9-2004 |
Your thermostat most likely is bad news. The correct thermostat functions to close off the bypass as the thermostat fully opens. If you just got something from Parts-R-Us that fits in the hole for a couple of $, it is not closing the bypass when it opens up. As a result about 1/3 of the water flow is bypassing the radiator. Yep, shur-nuff that will make it run hot. If you just take out the thermostat all together, it will also run hot for the same reason. However, for a short run, it will not hurt much. Second problem, if no water comes out when you open the drain tap, then it is plugged up with crud. Let us hope that it is only some sediment that has settled out in the drain just ahead of the valve. Take the valve off and see if the water will then gush out  . If you have to poke in there with a srewdriver to get a trickle to come through, you need to do some serious cleaning . The side plates must come off and then you dig and scrape. If it is really bad it may be engine out and head off to get it cleaned out. Extreme cases where the block is full of a mixture of rust and hard scale, you could be working literally for over a week after you completely strip the block and take it outside for application of chisels and a high power pressure washer. Cleaning out a cruded up block is no fun at all. Your overheating problem may be related to the block being full of crud. If the water cannot flow freely through the block, then you are not going to have much water flowing through the radiator either. Also, if you have places inside the engine's water jacket that are full of crud, these will be local hot spots, and by that I mean really hot, as in boiled dry and damage to the nearby components, like cracking your block, or seizing your pistons or other unpleasant events. Get the crud out, and get a proper thermostat. | |||
| KC Unregistered guest Posted From: 168.209.98.67 |
Hi Bill Thank you very much for the advice. What you say about the thermostat and it blocking off the by-pass now make sense, as the previous owner had blocked off the by-pass with a rubber plug. I presume this was an attempt to make the non-standard thermostat work properly! I will order an original from the UK. Any suggestions? Jack Barclay? The side plates you mention, are they the round plates I see on the side of the engine? Hi KC, please register as a user of our site so you do not have to wait for your messages to be posted - congratulations on the new acquisition and remember David's Law [with apologies to Murphy who started it all] "the more trouble you have immediately after purchase then the happier you will be in the long-term as you find out all the problems straight away and can fix them at one time" the converse law being "if you do not have any problems straight away; you will have a long series of problems that have to be attended to individually usually after you have just reassembled the surrounding components after fixing a separate problem"!!!! (Message edited by david_gore on October 05, 2004) (Message approved by david_gore) | |||
| Bill Vatter New User Username: bill_vatter Post Number: 5 Registered: 9-2004 |
KC, I perceive you are new to RR ownership. The first and most important rule of mechanical work on these cars is to proceed slowly and methodically, knowing exactly what you are doing before you begin. Proceeding with haste is the most sure way to get into serious trouble. Possibly you know this already. Please excuse me if I have said offensive words here. Yes, the three round cover plates on the right side cover the largest holes in the water jacket. Getting the covers off will not be easy because the screws will have rusted, and they will not come out willingly. If necessary, I can coach you on how to get the covers off. I suggest you first remove the drain cock and the short adapter pipe immediately behind it. Then probe into the water jacket to see if you can determine how deep is the crud. The bottom of the water jacket is fairly level the full length of the block. This is about even with the drain, just above the oil gallery which runs the whole length of the engine and which you can see as a bulge along the length of the block. If there is only about an inch deep of crud, it will not seriously affect engine cooling. Much more than that and you will need to get it out. If not too deep, you just need to get the drain running freely, and change coolant often until you have the engine out for overhaul, which is hopefully many years in the future. Let us know what you find before trying to take off the round covers. You must proceed very carefully to remove the covers or you will tear up the screw slots and then you will have to drill the screws to get them out which you probably cannot do very well without removing the engine. For your thermostat, the parts suppliers in the UK are usually competetive in price, and the ones I have traded with sell good merchandise. These are Jack Barclay, Ristes, Introcar, and Brian Thompson. Best wishes for finding only a small amount of crud in the water jacket. Bill | |||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 378 Registered: 4-2003 |
Bill, Your comments are well founded. First, given that the cooling system suddenly went bad with a decent run, would you not agree that it's the oldest thing in the cooling book: a large bunch of crud and gunk came loose as soon as the cooling system was asked to do some extended work ? The stuff goes straight to the radiator and blocks it quickly ? I have seen this so often with these cars when less than 40% inhibited ethylene glycol has been used for some time. A serious power back flush can help, but often only clears a third or so of the radiator passages. Also, a long hard run with a very strong cooling system cleaner (ie two cups of domestic dishwasher powder) can rid the solubles. Of course a few very thorough flushes afterwards are needed. Secondly, the thermostat type and bypass are important in these cars. If the bypass is blocked off to allow the use of a conventional one, the cold motor will develop damaging hot spots, especially around the exhaust valve seats. The exhaust valve have coolant pumped directly to them individually by the distribution pipe before it reaches anywhere else. If the bypass is blocked and the thermostat closed there is no flow at all. In an emergency, a restricted bypass is better than a blocked one, and a conventional thermostat is better than none as it will at least protect against cold seizure of the pistons. Thirdly, I agree that it is extremely unlikely that any of the water jacket covers will come off in-situ. Invariably, even with the motor out and using a screwdriver press, at least half the screws will shear. Best go poking around with wire and compressed air through the drain plug and water pump openings. As you imply, the motor will be fine with an alarming level of crud provided it is stable. I have often wondered on the temporary use of some sort of wire mesh filter for the top hose for use when gunk is likely to come loose, such as after storage. The mesh need not be very fine: just enough to stop particles large enough to lodge in the radiator passages. Ideas ? | |||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 260 Registered: 4-2003 |
Well Richard's suggestion for a filter has been heeded by a little old lady in Queensland. She actually crochets something that looks like a coarse woven condom that slips into the top pipe of the radiator header tank, is doubled back over that pipe and the hose forced over it to hold it. It is so simple to remove, shake the gunk out rinse and refit. I have yet to track her down and will see if she will offer her wares!! The toe of panty hose also works but given their fragility don't last long. Richard's remarks on core blockage is so true. Many times I have seen overheating approached with a good flush and a new core. The flush invariably loosens more gunk up and the new core gets blocked again. Fixing the problem without removing and stripping the engine is hopeful band-aid action in my experience. Elsewhere we have given a fair amount of space to advices on cleaning the blocks and these should be read by our enquirer. | |||
| John Dare Unregistered guest Posted From: 144.138.194.134 |
I think someone advanced the idea of "putting a sock in it" (a great idea) and even marketed a simple textile device describing same as a filter "sock". Conceived in Australia and although not an earth shattering "invention", was indeed advertised in U.S magazines/journals for a short time. It fitted inside the upper radiator hose. (Message approved by david_gore) | |||
| Bill Vatter Experienced User Username: bill_vatter Post Number: 6 Registered: 9-2004 |
Richard makes a good point that sudden onset of overheating problems is likely a good clue to the problem being experienced. KC, with what can you associate the onset of overheating? Aa large lump of crud comming out from the engine to lodge in the radiator seems unlikely to me. Of course if it has happened that is proof there is a concern, but consider this: The rust deposits form as silt, whicl settles out of suspension in the coolant when the engine is stopped. The silt that settles on a high-flow place gets picked up again when the engine is restarted, but that which selttles into a low-flow region (bottom of the water jacket) just stays there forever. That is why the rust piles up on the bottom of the water jacket. So how is it that clumps of crud get picked up after cleaning? You can get an infra-red temperature sensor for about $100 US that will allow you to point at different places on your radiator to read the temperature. This will tell you if there is a cold spot. A cold spot indicates plugging. I have heard about the diswasher soap treatment. I have used that myself, but I think all chemicals that will not disolve important components you want to remain intact are not very effective against rust and scale. However to entertain readers with some humor, I once poured a good bit of gear oil into my radiator, and the dish soap is very good at getting gear oil out. The bottle of gear oil looked very much like the bottle of antifreeze. Both were up on a high shelf, and I just reached up and grabbed the wrong one. As I poured, I thought, "Hmmmmm, this antifreeze is yellow, not green, and it seems very thick. Hmmmmmm. OH ******! THIS IS ****** GEAR OIL! *******! Well if you ever do that, dish soap will fix the problem, but you have to rinse and rinse and rinse to get the soap out. Remember I said approach all tasks methodically making sure you know exactly what you are doing? I learned that the hard way. | |||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 379 Registered: 4-2003 |
Bill V, agreed. The last time I had this problem on my R-Type was in the 1970s. By a bunch of crud, I mean a few handfulls of lumps of ceramic-like pellets around 3mm in diameter, not just one lump. With diligence I eventually got all the loose stuff out until no more came free, then had the radiator cleaned out a few months later (tanks off, clean the tubes out with brass rods), and never had a problem again. The symptoms were the same as KC's. Using an infrared thermometer on the radiator is ideal, but back then they were expensive lab tools. As a guide, with the motor running too hot, simply stop the car and immediately run the back of your hand across the radiator core. There were always very obvoius cold (blocked) sections and very hot (clear) ones when the radiator was playing up. The trouble is that flushing makes the clear passages very clean, but it is extremely difficult to do anything to the blocked ones, typically 2/3 of the core, unless a very high-flow power flush is used. That can of course have other consewuences. When I had the block tank-cleaned on the next overhaul in the 1980s, all the crud was finally removed. These cars run fine with up to half the core blocked !! Mine was running fine, but there were signs of seepage last year from the lower tank solder joint. I had the core, the original, replaced, rather than have it cleaned out again (I had already had three leaky tubes soldered up as blanks in the 1980s on having the radiator cleaned). Clearing the tubes with brass rods is the only sure way, but there are always casualties with severely blocked tubes. Even running 40% glycol for the past 20 years, the old core turned out to have been at least 1/3 blocked by last year. Despite that, it was showing no cooling problems at all. Anyhow, I am going to fit some coarse wire flyscreen mesh in the top hose at the radiator and see if it catches anything. The car runs 50% glycol. | |||
| KC Unregistered guest Posted From: 168.209.98.67 |
Thank you very much for all the advice so far! Herewith answers to some of your questions: David – Thanks, I have now registered, and await approval from the moderators. I agree with you about experiencing all the problems early during ownership. These cars are typically not used a lot, and if someone is selling, I bet it has stood for a long while before the decision was finally taken to sell. I had the same experience with my Shadow, which suffered from lack of use. I did more mileage in one year than he did in 16 years! Bill – This is my second RR, but this car is totally different so it’s a totally new learning curve. I was able to obtain very detailed documentation on maintaining my Shadow, but with the Mk VI even the service sheets are rather sketchy. In view of this I really value this forum and all your advice. Hopefully I will be in position to help others once I gain more experience. I don’t see myself selling this vehicle soon! I tried to remove the drain plug last night, but did not succeed, as I am worried that I might damage it. However, once I removed the pipe that directs the water flow to the ground water started trickling out of the drain tap, so there is some progress! How do I remove the drain tap from its adapter pipe without damaging it? It does not seem like it will take a tool of some sort. I will follow your advice and will not remove the cover plates unless it becomes totally necessary. However, there does not seem to be any rust on the screws, so they might come off OK. There is a cover immediately above the drain tap. Perhaps I should try that one first, as it is accessible. Can you perhaps direct me to the websites of Introcar, Ristes and Brian Thompson? I have already sent e-mail enquiries to the others, and await response. Richard and Bill – The sudden overheating occurred after a long hard run on the open road. The interesting thing is that it runs slightly hot in stop / start traffic, but overheats as soon as I get onto the open road. Prior to the overheating the car ran very cool, almost cold. The temperature gauge would seldom reach the centre mark. Another question. I found a rubber O-ring inside the radiator, near the filler. Does this belong on the radiator cap? I also noticed that I could easily remove the radiator cap while the car is at operating temperature. Is this normal, considering that the system operates under pressure? Thanks again for all the advice and comments. It would be very daunting trying to try and maintain a car like this without been able to learn from the experience of others. Regards KC (Message approved by david_gore) | |||
| Ashley James Unregistered guest Posted From: 62.255.0.5 |
In my experience most old engines have a couple of inches of crud in the block but do not obviously overheat. If the tap and its adapter tube are removed from the block, the thermostat removed and hose put in, you will probably be able to empty the block by poking a screwdriver in and waggling it about. If the engine has boiled it will transfer some of the crud to the top of the radiator and re-coring is the only safe option. If the ambient temp is high (30+) and you drove in excess of 65mph, then it may well have boiled the engine. Earlier cars had very restrictive shutters on the radiator so that above this speed the temp just keeps rising. Otherwise I doubt crud in the block caused a sudden tendency to overheat. (Message approved by david_gore) | |||
| Norman Geeson Unregistered guest Posted From: 80.40.98.77 |
KC, BIll & Richard All of what has been said is true. But according to the chassis number of this car, providing it is original, it also has other problems. The radiator type will be the shallow type which is more likely to draw silt into the bottom hose outlet and collapse the bottom hose at higher RPM.The block has limited access as it only two circular side plates, with a plug in the centre position. Making matters worse will be the original ten piece radiator shutter which may not have been modified to open out the shutter angles. It will also have the very early water gallery which is restricted on its outlets. In its favour is that the block will have seperated parent bores which will help cooling provided they are not blocked. Using any none original type of thermostat will definately cause problems. Ristes of Nottingham have produced a very cheap top hose textile filter for about 15 years to my knowledge. Everything being equal it is likely the engine needs removing to de-silt the block. Certainly any continual overheating will for sure cause eventual piston damage. Regards Norman Geeson (Message approved by david_gore) | |||
| KC Saayman Yet to post message Username: kc_saayman Post Number: 1 Registered: 10-2004 |
I finally managed to remove the drain tap, which resulted in water gushing from the hole! It does not appear that the block was restricted, just the tap. I am most relieved! The radiator also seems OK, as water flows seemingly unrestricted when flushed. I tested the aftermarket thermostat, and found that it opens a little late at about 80 deg, and not 75. It also closes almost immediately when I remove it from the pot, which does not seem right. I will order an original thermostat, which will take at least three weeks to reach me. However, I would like to use the car to a club outing on Saturday (only about 70 km), so what should I do in the interim? My options are as follows, I think: 1) Block the by-pass, and run the car without a thermostat. Warming up should not be a problem, as I live in a hot climate. Current temperatures average at about 30 deg during the day. 2) Block the by-pass, and run with a new after-market thermostat, as the previous owner did. In this case, there will be no water flow before the thermostat opens. What happens to the water pump, which will try and circulate the water? 3) Partially block the by-pass, and run with the after-market thermostat. Will enough water still flow to the radiator for effective cooling in our hot climate? These options are very short-term solutions, and I will probably not drive the car again after this weekend, until I receive the original thermostat. Regards KC | |||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 382 Registered: 4-2003 |
KC, I still believe your radiator is partially blocked. As others have pointed out, it all started after a good run when all the muck would have been stirred up. I would go for Option 3 for now. Be aware that a new genuine thermostat is quoted at well over £100 in most cases. Also, aftermarket (ie wax pellet) thermostats almost always open at higher temperatures than the original bellows type. The one you have seems to work fine. If it opens fully, it is almost certainly not defective, and yes they do close very quickly when out of the pot. There were many coolant pressure regimes with the Mk VIs: finally, they were left unpressurised with a hole drilled through the valve plunger, hence the need for a lower operating temperature. If the bypass is blocked and the thermostat closed, the water pump will simply cavitate. That is no problem at all. The problem is the hot spots developing especially around the exhaust valve seats due to no coolant circulation. Your contacts: Brian Thompson, 119 Station Road, Warboys, Huntingdon, Cambs. PE17 2TH Tel: +44 1487 822488 Fax: +44 1487 822488 Contact: Brian Thompson New and used parts specialist 1920 - 1980 (this was formerly the company Adams and Oliver dating back ove 50 years) Ristes Motor Company Ltd, Gamble Street, Nottingham. NG7 4EY Tel: +44 115 9785834 Fax: +44 115 9424351 Contact: Steve Lovatt Specialists at restorations across whole range of models. Extensive parts manufacture especially for pre-war cars. Introcar www.introcar.co.uk sales@introcar.co.uk +44 20 85462027 (tel), +44 20 85465058 (fax). For Mk VI ask for Struan. Also see: http://www.expconnect.co.uk/rrbsa/memblist.html | |||
| Chris Gillings Moderator Username: chrisg Post Number: 28 Registered: 5-2001 |
Bess, my Mk VI, has exhibited overheating on numerous occasions. Crossing the Hay Plains in January '95 I found I was governing her speed by the temperature gauge rather than by the speedometer. We couldn't keep her above 60mph for more than a few minutes before the gauge headed into the red; dropping back to fifty brought the temperature down quickly enough to feel safe. Leaving Adelaide later that month the radiator blocked completely (on the first stage of the climb up Eagle whatsit). The NRMA flat-bedded us to a radiator shop that had an incredible backflush system - I thought Adelaide had water restrictions but this was worthy of a fire station! The colours of the water that came out of the radiator were many until eventually it ran clear. We proceeded to Sydney and found that we could maintain up to 65mph without overheating. On several occasions since that trip I have noted that above 65mph the car gets into a state where it simply cannot dissipate the heat load at a rate equal to the engine generating it. The temperature just keeps climbing until you have no choice but to slow down - usually to 35mph or so. This behaviour has persisted despite the installation of a new radiator and a thermostat with holes drilled in it (by John Vawser) to increase flow. I'm inclined to agree with Ashley that it's due to the shutters being too restrictive. Perhaps it's time to follow Tony Ward's instructions on rectifying this in the Mk VI? # Increasing Air Intake on Early Post-War Cars (Message edited by chrisg on October 07, 2004) | |||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 261 Registered: 4-2003 |
Chris I suggest that that is a bit of straw clutching to contemplate shutter adjustments. It spoils the car's appearance and was only necessary on the very early Bentleys. Your engine has a 4 1/2 litre block which has much more capacity for flow than the earlier 4 1/4. The problem I suspect is that the water simply cannot get through the block because of the crud in it so all the cooling facilities in the world aren't going to control the temperature. The added worry is that if the block is as bad as I suspect it is you will be generating hot spots which can seriously damage the engine even structurally by cracking the block or head or both. Have you removed the side plates on the block and had a good look? One test I would consider is to remove the thermostat completely and block off the by-pass. Then try your 70 mph run and see whether the temperature improves. I suspect it won't. And as others have described ad nauseum, by now some of the the crud will have flaked off and will have partially blocked your new radiator core. Again pass a typhoon through there and you won't get any more cooling. The only solution in my humble opinion is to bite the bullet and clean the block out which will probably require removal and stripping of the engine. Somewhere in this system I recounted the problem I had with my 4 1/4 Dawn SDB94. After a complete overhaul and soaking the block in a propriety hot tank for a whole week, the engine would overheat in much the same way as you have experienced. I stripped it again and cleaned the whole cooling chamber out with acid and the block finished up cleaner than new. My new radiator had to be opened up and rodded to get the crud out as well. Subsequently I drove that car flat out at 94 mph on a stinking hot day for nearly 20 minutes and it never went above 78 degrees C. And as far as I know the car has had no heating problems since. | |||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 383 Registered: 4-2003 |
I have shared similar experiences to Bill's on my R. The first time I pulled the motor down was in 1972. By then, the one bout of overheating had been solved (not cured permanently) when York Motors cleaned out the radiator with rods and scraped away at the water jackets. I had the block in the hot brine tank at Berco in Canberra and thought it would be clean. By around 1981 it was getting wobbly again. I had the block dunked in Repco's hot acid tank in Canberra. Boy, that cleaned it up alright. I forgot to remove the small aluminimum patch on the side of the crankcase, presumably covering a hole for a mechanical fuel pump. It completely dissolved away. Since then, full bore in any temperature leads to below 80C. I have driven quite some distance with the speedo off the dial in searing heat (the cops were less sophisticated, and I always chose their changeover times for my monthly trip from Sydney to Canberra in the 1980s). I remember Bill's acid tricks on the Dawn, and seem to remember he used several litres of HCl. Didn't you do it in-situ ?? Martin: I know that feeling well. Everything is OK until you hit 70mph. Then the needle heads steadily off the dial unless you slow down. In my car, it has always been caused by a blocked radiator, however new the core is. I like the sound of Ristes' wire mesh insert. The last time I drove it on the highway was in 1992. It was showing slight signs of trouble ahead, so I was not at all surprised to find last year that it was 1/3 blocked. I was always trying to dream up a removeable header tank to bung some long pipe cleaners down the holes every 6 months or so. Anything is possible, but I never did get around to it. The trouble is that, under most conditions, the radiator is way oversized, and the flow rate so slow that there is nothing to blow any much through the side tubes. They just silt up slowly like a mountain lake. The irony is that a smaller core would probably last far better and still do the job. | |||
| Bill Vatter Experienced User Username: bill_vatter Post Number: 7 Registered: 9-2004 |
KC, Not to repeat what others have said, I think you would get maximum cooling if you block the bypass completely and remove the thermostat. Block the bypass by removing the hose and putting something in it that cannot possibly come out and go into the water pump to destroy the impeller. A bit of large diameter rod or a short piece of large daimeter screw should do it. | |||
| Laurie Fox New User Username: laurie_fox Post Number: 2 Registered: 6-2004 |
KC has said that the block appears to be reasonably OK and that the radiator also seems to be fairly clear. In that case there should be reasonable circulation of coolant provided the pump is working. Why not check by putting a long flexible pipe on to the thermostat pocket outlet, pointing it into the open radiator filler hole, starting the engine and seeing what happens. | |||
| John Dare Unregistered guest Posted From: 144.138.194.141 |
I agree.. forget "theories", some of which, whilst quite sound, could keep hapless owners awake at night as they agonize over which one could be "right". Lets start with some BASICS, otherwise KC might be depressed to the point that he buys an air cooled "VW"!. Does the coolant pump not only rotate, but does it PUMP?. I pulled an early MK6 pump recently and discovered that only one and a half paddle /blades remained on the impellor. Assorted pieces were jammed in the lower housing, other parts long gone (somewhere) (Message approved by david_gore) | |||
| KC Saayman New User Username: kc_saayman Post Number: 2 Registered: 10-2004 |
Thanks Laurie and John, I haven’t thought about testing the pump. That’s a good point. Regards KC | |||
| KC Saayman New User Username: kc_saayman Post Number: 3 Registered: 10-2004 |
I have just tested the pump, as suggested, and it seems to work very well. Everything has been cleaned and reassembled, so I will test drive the car in the morning. Regards KC | |||
| Ashley James Unregistered guest Posted From: 62.255.0.5 |
Usually blades come off the water pump rotor because the bearing has collapsed and they have hit the main casting so, unless this has happened, I would assume it is working correctly. (Message approved by david_gore) | |||
| John Dare Unregistered guest Posted From: 144.138.194.134 |
NOW lets see what happens when you fit your new, correct, original type thermostat and adjust fan belt tension etc. The best of luck to you, hoping that engine disassembly to purge block, is not (yet) required at this stage. (Message approved by david_gore) | |||
| Laurie Fox New User Username: laurie_fox Post Number: 3 Registered: 6-2004 |
KC So we now know that the pump is working. The results of your test drive will be interesting. I would expect that the problem has not gone and I suspect air being trapped in the radiator core. If you get unduly high temperature on your test drive stop in a quiet spot, lift the bonnet and, with the engine stopped, listen for any sound of air bubbling out the radiator tubes into the header tank. If you do hear anything note how long it is before the bubbling stops which may possibly be several minutes. Then drive on and you may find that the coolant temperature is normal for a while and then rise again. How far did you drive before the temperature rise for the second time, at what speed and were there many corners on the way (lateral acceleration will uncover the tops of some of the radiator tubes and let air in). I know that you have said that water flows seemingly unrestricted when flushed but often you will find that a radiator full of water will drain out very quickly although with a bung in the outlet at the bottom it will only fill slowly. There is a big difference, sometimes, between flow test results depending on whether the radiator is full of water or air to start with. Another small point is to make sure that there is sufficient coolant in the system. I know that this is obvious but there may be an air lock somewhere. The standard arrangement with the Bentley thermostat deals with this in one of two ways. Early thermostats had no air leak hole in the main valve and in order to avoid an air lock it was necessary to remove the air bleed screw at the side of the thermostat pocket ( on the left hand side) and fill with coolant until the coolant came out of the screw hole, then put the screw back and put the rest of the coolant in. This screw also locates the thermostat in azimuth. Later thermostats had a small air leak hole in the valve head complete with a separate little valve in the middle of the small hole and it was not necessary to undo the screw at the side of the thermostat pocket (just as well in view of all the corrosion which goes on in that area). Your thermostat is different - does it have an air bleed hole or not or is it a loose enough fit for the air to get round anyway? The design of the pump itself is such that it is liable to cavitation if there is any restriction on the inlet side and you may be slightly worse off than others in this respect because I suspect that you are significantly above sea level. But I have found that running with the by pass open and the thermostat removed there is an improvement in pump performance which more than outweighs the slight reduction in the proportion of water going through the radiator. I know that this involves a slower warm up from a cold start but this does not worry me as for 90% of occasions the engine is prewarmed by a block heater on a timeswitch in the garage set to come on every morning. In any case the increase in warmup time is quite low. Running temperatures with this arrangement are about 10 deg. lower than the normal 78 deg. C and the heater still works extremely well. I like this because it means that the back of the engine (Cyls 5 & 6) is no hotter that it should be and the rest is slightly cooler. However, I must admit that I rarely drive at more than 70mph these days and then only for quite short distances. These findings came from various experiments I made on the cooling system two or three years ago. At the end of 2003 Norman Geeson made a posting on this Bulletin Board asking for information about filler caps on header tanks. I responded by email and included a write up of the results to that date which I do not now need to take any further. You might like to see what I said then and so this email is shown below. ************************************************************ Subj: MK VI Radiator filler cap positions Date: 24-12-03 To: (Email to Norman) Norman In response to your RROC(A) website posting here is some information about my Standard Steel Saloon B420EY which you may or may not find interesting/useful. I am the third owner and purchased the car in 1959 with 97,000 miles on the clock which I have every reason to think was the total mileage run up to that date. It appeared that the original 23" radiator core was still in place and it had a side mounted filler cap. Since then it as been our only car with 408,000 miles on the clock now and is, at present, fitted with radiator No 4. I have been the only driver over the whole period, except for short test drives by MOT testers, etc. The original radiator (No 1) was replaced at 154,139 miles (high coolant temperature and slight leak from middle of matrix) with a service exchange unit (radiator No 2) from Jack Barclay which had a 23" matrix and a side filler cap. Radiator No 2 ran until 252,529 miles (high coolant temperature and slight leak at top of matrix where it is joined to the header tank) and was replaced with a service exchange unit from James Young (Radiator No 3). This also had a 23"matrix and a side filler cap. It seemed that the original windscreen demister arrangements with a metal tube and two short rubber connections between the radiator collector box and the bulkhead were too rigid and that vibration was tending to cause fatigue fractures in the soldering of the radiator tubes to the header tank. So the connector pipe and the collector box were not refitted when radiator No.3 was installed. No.3 radiator was on the car when it had it`s major overhaul in the 1980`s and may well have been left empty while this was being done. By the time 385,857 had been reached radiator temperatures on normal driving were beginning to rise and Radiator No.4 was purchased from Introcar ready for installation later (also 23"matrix and side filler cap). However, since I had by that time retired, and there were times when the car, though still in daily use, was only doing short journeys on mainly flat ground, I thought that would be a good opportunity to find out a bit more about what was going on in the cooling system. Regular radiator and block flushing has always been carried out on all of the radiators with occasional removal of the block drain tap so as to be able to poke about inside. But the standard arrangements are not very convenient and the standard drain tap was replaced by an industrial straight through type cock which could be rodded through with a stiff wire if the coolant was slow to emerge and easy to dismount when necessary. The outlet from this cock is, of course, horizontal and I have a right angle bend which can be easily fitted on to divert any rapidly emerging coolant down into a bucket and then taken off afterwards. So the investigations into radiator No.3 began with frequently repeated flushing and back flushing of both radiator matrix and cylinder block with the thermostat removed and the by-pass to the water pump closed off with periods of driving the car in between. The car as a small water pump pulley, fitted with the large fan. With everything as clear as possible on a flushing only basis we can now start to measure something. The first observation is that with the radiator initially empty and filling in the normal way we find that the water does not go in very quickly. Filling the header tank so that all of the tops of the radiator tubes are covered results in the water not going into the matrix at a reasonable speed and the water level in the header tank only falls slowly so the process has to be repeated until the system is full. So what is stopping the water going into the matrix - is it limescale deposits, is it other harder deposits or is it air getting trapped in tubes which are now too narrow? The next stage was to investigate the filling process further. This was done by disconnecting the radiator from the engine, top and bottom, closing the bottom drain tap and putting a rubber bung in the outlet from the collector tank and the bottom of the radiator. The header tank was then filled quickly and topped up progressively as the level went down. Air bubbles could be heard rising out of the matrix tubes until all of the air had been expelled and this lasted for nine minutes. The radiator was then treated with Radflush No.1 (2 hours at 140 deg.F) which was circulated by an external pump and heat exchanger, in at the bottom of the radiator and out at the top. Then another drain, flush and reverse flush and a repeat of the test to see how long it takes for the air bubbles to clear - this time it was 1 3/4 minutes. Then, a day or two later, the radiator was treated with Radflush No.2 by putting the Radflush into the radiator with the engine connected to the radiator in the normal way. The engine was run for about 15 minutes and the solution drained off at the radiator drain tap and at the cylinder block. Then flush and reverse flush, first in at the filler cap and out at the cylinder block drain, then the other way round. Then repeat the test to see how long the air bubbles take to clear when filling an empty system. This time it was 1 1/4 minutes - not very much different from the 1 3/4 minutes recorded before and possibly influenced by the fact the for the last test the radiator and engine were connected normally. So the Radflush had made some improvement but not nearly enough to establish reasonable performance and it seemed that air trapped in the radiator was at least part of the problem. This seemed to be consistent with the fact that when driving the car at that time I could drive for about 11 miles first thing in the morning after the car had been standing overnight with the radiator thermometer showing a fairly normal reading - then the temperature would rise and not go down again. However much coolant there is in the header tank the tops of the tubes on each side of the radiator will be above the coolant level to some extent due to lateral acceleration on corners. This will certainly let some air into the radiator, but why does it not get out again of it`s own accord? The next tests seemed to throw some light on this situation. The bottom radiator hose was removed and the radiator drain tap closed. The garden hose was then set to deliver water into the radiator filler cap and turned on. With the radiator initially empty and thus full of air the header tank quickly becomes full. Now turn the hose delivery down progressively until the header tank level drops and then adjust the hose delivery until the level of water in the header tank stabilises at about halfway. The hose delivery rate, at this point, equals the rate at which water is flowing into and out of the radiator - only 1 gall in about 2 minutes. If, however we put a bung in the bottom radiator outlet, fill the radiator fully and let all of the air bubbles work their way out and then quickly remove the rubber bung we find that the radiator empties itself very quickly indeed. If we repeat this and feed water from the garden hose into the filler cap as soon as we remove the bung we find that the header tank will empty and remain empty although the hose is delivering about 4 galls per minute - the highest rate at which it would deliver. So if there is air initially in all of the radiator tubes it mostly remains there and does not get out either by bubbling up out of the top of the tubes or being carried down by the water and thus out of the system, but if there is no air to start with the water meets much less resistance. Testing the reconditioned radiator (No.4 - available but not fitted) resulted in the 4 galls per minute going through completely unobstructed as might be expected. So the air must be being trapped by the hard deposit remaining after the limescale had been removed and the overall reduction in cooling effectiveness must be due to the combination of the hard scale and the air which it entraps. Can these two factors be separated? That was the object of the next test which was to rearrange the coolant system so that the hot coolant went in at the bottom of the radiator and out at the top on the basis that although the downward water flow was not high enough to clear the air the upward flow might do the trick. Possible rearrangements of the piping were limited. Ideally it would have been nice to have been able to take the header tank off and make more substantial changes but I was limited to what could be done without dismounting the radiator and thus putting the car out of action for a longer period, but what I was able to do did result in useful information. To provide a feed from the top of the header tank to the pump inlet I was able to cut a hole in the header tank immediately under the filler cap which would take a normal 22mm domestic water tank connector and insert a cover plate about 3/8" above it so that the pump suction could pull coolant only and not a mixture of coolant and air. Obviously this cannot work unless there is more than 3/8" of water in the header tank on the nearside and this means that these will be no coolant supply on any significant left hand bends. I was prepared to live with this for a limited period. The next point was to provide a small bleed in the rearranged piping so that the system could be filled properly and no more air get trapped subsequently. The third point was to mount a pressure gauge on the instrument panel where it could be seen when driving and connect this to the radiator drain plug via piping which had its own air eliminating bleed. The subsequent driving tests were interesting. Everything worked pretty much as expected and any air which got into the system on left hand bends was very rapidly eliminated. Cooling was improved to a useful extent, probably about 10 deg.C, but there was a high pressure drop across the radiator itself (5 lb/sq in at a little over 50 mph). I did not explore the situation above 5 lb/sq in since I did not want to subject the radiator to a greater pressure. The next thing was to consider what comparative readings could be taken once radiator No.3 had been removed and No.4 installed (which was actually done at 400,800 miles). It was not practicable to try to reproduce the hot in bottom cold out top arrangement but it would be very desirable to be able to get some indication as to the extent of the expected flow improvement. So while radiator No.3 was still installed the hot in bottom cold out at top piping was removed and the pressure gauge visible from the driving position was connected to the cylinder block drain point. It seemed unlikely that any air bubbles would get into this gauge pipe connection and so no special air bleed arrangements were made. A little dissolved air might come out occasionally but this could be dealt with by bleeding manually if required. At this stage the thermostat was still out and the bypass still blocked so the total restriction from the cylinder drain point to the header tank was the same as it would be with radiator No.4 and pressure gauge readings as between No.3 and No.4 should be related to relative rates of flow. As expected with No.3 radiator the readings were so low that great care had to be taken to get a reasonably accurate figure. The car must be travelling on level ground and at a constant speed since attitude differences and acceleration/deceleration both produce pressure reading variations. The pressure gauge height above ground is very nearly the same as the coolant level in the header tank, on level ground, so there is no correction constant to be taken into account for height differences. Opportunities for level ground and constant speed driving seem to be remarkably few just when you want them but a figure of 0.4 lb/sq in was finally established reasonably accurately. With No.4 radiator installed the corresponding reading was 1.0 lb/sq in. In each case increase or decrease from 40 mph resulted in a rise or fall in pressure reading closely in proportion to the square of the speed, as would be expected (all readings in top gear). Since flow rates can be taken as being proportional to the square root of pressure this suggests that flow rates, at least at the lower speeds are proportional to speed and that the flow rate for No.3 radiator was only 63% of that for No.4. In both cases, with no thermostat, the radiator thermometer goes up when climbing hills and down when descending but does not stabilise quickly enough the give a reliable indication of coolant temperature during the comparatively short periods of steady speed on level ground, which is a pity. As I said before, with No.3 radiator, there is an initial period of better cooling before air gets into the radiator and all of the level running/constant speed checks were done after the air had had a chance to get in. The next test produced a result which surprised me. I unblocked the by-pass and restored the original connection between the thermostat pocket and the water pump, still leaving the thermostat out, expecting that the pressure gauge would then indicate lower readings than before. In fact the readings increased from 1.0 lb/sq in to 1.3 lb/sq in at 40 mph and from 2.2 lb/sq in to 2.8 lb/sq in at 60 mph. So what is happening is the region of the by-pass? Is the water being sucked into the thermostat pocket or is it going in the reverse direction? In either case the situation in the region of the water pump impeller will be different to what it is in the by-pass blocked condition and the pump characteristics may then be changed, perhaps substantially. I know of no way of investigating this further other that putting pitot tubes, preferably with static heads also, into the piping at various points and trying to interpret the reading from the highly turbulent flows. Unfortunately this is well beyond what I can do. It may be that even at low pump speeds, without a feed from the by-pass there is some cavitation at the pump inlet. If so this might explain the high pressure across the radiator matrix when the flow direction there was altered from down to up, since the pump inlet pressure would then have been higher and the pump that much more effective. So what conclusions can we draw from all this? With a new radiator there are no problems and any air which gets in does get out, one way or another. With an old radiator air seems to get in and stay in once the tube blockage has reached a certain critical stage but by that stage the radiator is due for a change anyway. There is one more change still to be made and that is to put the thermostat back and I may get round to doing this when the weather gets warmer but you will appreciate that since I had my 88th birthday last June I am not too good in the cold. This will introduce changes in the system while the system is running. We have to remember that the thermostat is bellows operated and that the bellows itself has quite a low spring rate. That is to say when the water is nearly but not quite at the temperature which would cause the thermostat to start opening if it were in a saucepan of hot water the pressure of the water in the thermostat pocket will cause it to open and start feeding water through the radiator. At a slightly higher temperature the thermostat valve will be "fully floating" and highly responsive to changes in water velocity. This seems to me to explain why the radiator thermometer under normal conditions of driving never seems to depart from 78 deg. - it is the water movement which is modulating the thermostat valve, not the temperature. If this water modulated movement is not sufficient the keep the temperature close to 78 deg. then the datum will move up to a slightly higher temperature and the water induced modulation will continue from that point. If things get more intense the datum will move up more and high water flow will close the bypass fully well before the 92 deg. or so when it would normally be fully closed in a saucepan. It will be interesting to see what the pressure gauge indications are when I get round to it. Apart from the tests with the by-pass open all of the above checks were done quite a long time ago. There is a very brief summary in my reply to a topic on "Mk VI radiator shell" on the BDC website started by csimmers in January 2001 but this is the first time I have got round to anything like a full write-up. Radiator No.3 is still in my garage and has not been touched since it was removed from the car and I still have all of the fittings for the down to up flow modifications if anyone else would like to take this kind of investigation further. It would be comparatively easy for someone else to repeat my radiator No.4 tests with the by-pass blocked and unblocked (and the thermostat out) and see whether they find a higher than expected pressure at the cylinder block drainplug when the by-pass is not blocked. Both the heater and hotspot coolant circulation circuits were in operation all the time. What was going on in region of the water pump drain hole and it`s connection to the cylinder block in unknown. Comments and/or queries welcomed. Regards Laurie Laurie Fox, 7A Lynwood Road, Epsom, Surrey, KT17 4LF. Tel 01372 724757 **************************************************************** | |||
| KC Saayman New User Username: kc_saayman Post Number: 4 Registered: 10-2004 |
Hi all Thanks for all this information Laurie! Very interesting read. Your comments about air trapped in the radiator sounds very plausible, as I could hear bubbles. I will pay more attention to this. My Thermostat housing does indeed have the air bleed screw. I filled the motor with 50/50 coolant and water mixture via the thermostat housing, before fitting the top radiator hose. The radiator was the filled separately. Hopefully this eliminated some air getting into the system. I took the car for a drive this morning with the overflow blocked, and the thermostat removed. The foot of an old stocking (wife’s, not mine!) was placed in the top radiator hose to collect any dirt that may still be in the motor. On a short drive of about 10 km everything seems fine. The motor warmed up quickly to about 70deg, and seemed to maintain that without problem. When I stopped the temperature climbed to just over 75deg, but immediately dropped to 70deg once I started the engine again. That seems to indicate that the radiator is OK. Would you agree with this assumption? I still have to see what happens on a longer run. I now await a new thermostat, and will not drive the car much until it arrives. As we live in a very hot climate, I am considering installing an electric fan in front of the radiator, on a separate switch to assist the original fan in heavy traffic etc. It looks like my car is already fitted with the smaller fan pulley. How can I tell for sure? Thank you very much to everyone for helping me with this process! Kind regards KC | |||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 262 Registered: 4-2003 |
I write probably ill-advisadly slightly incoherant with the election of our new government. But one assertion made by our illustrious correspondent was to the effect that the little 2BA screw in the thermostat housing was a bleed screw. Surely the sole design purpose sir was to locate the bloody thermostat so that the side exit for the bypass did actually squirt the coolant down the appropriate tube! otherwise Sir! I am in complete agreement! | |||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 386 Registered: 4-2003 |
Bill, quite correct. It would be folly to attemp to remove the 2BA thermostat locating screw as it will probably snap anyhow. As for air in the system: maybe, if the head gasket has a minor blow. This is often brought on when the cooland after a long period with water is changed to glycol. Is there any trace of cooland appearing on the oil filler cap (white oil-soolant emulsion) ? That sometimes accompanies a gas leak into the coolant, but often boils away in a hot climate so you cannot see it. This fault is often ignored while frustrated owners spend a fortune on everything else first. In 1971, my father and I mad a test rig as shown in the grey book: Bill may remember it. Despite the radiator being 1/3 blocked, the time to drain was virtually identical to spec: 18 gallons at average 3 ft above the top hose took 80 seconds on the R-Type as it should (for a MkVI it should be 50 seconds). A partially blocked radiator core says little about flow rate and a lot about cooling efficasy. The water temperature will always rise when you stop (heat soak) and drop quickly when you start, again even with a dodgy core. Sorry to be the devil's advocate, but I put my chips both ways on a blocked radiator or a minor cylinder head leakage. Probably neither will show up in a compression test or flow test. The only way to diagnose a leaky gasket is with compressed air in the spark plug holes with the motor hot. | |||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 387 Registered: 4-2003 |
Sorry, I mean "That sometimes accompanies a coolant leak into the crankcase (oil), but the fluids often boil away in a hot climate so you cannot see it. This fault is often ignored while frustrated owners spend a fortune on everything else first.". | |||
| KC Saayman New User Username: kc_saayman Post Number: 5 Registered: 10-2004 |
According to the Service Handbook the thermostat locating screw doubles as an air release screw. You apparently have to loosen it slightly to allow air to escape. However, as you point out, it will probably break if disturbed, so I have decided to rather leave it well alone. A very recent compression check gave the engine a clean bill of health, but I suspect that the radiator can probably do with a good clean, especially in light of your comments that a partially restricted radiator will still work reasonably well. What is your opinion on adding an electric fan? That will present the opportunity to remove the radiator, so I can then have is seen to professionally. Thanks again for all your valuable input! Regards KC | |||
| Laurie Fox New User Username: laurie_fox Post Number: 4 Registered: 6-2004 |
KC I am not surprised that your short test drive resulted in no overheating. My No.3 radiator would go for about 11 miles before the temperature started to rise because it takes some time for the air to get into the radiator. In my case the air was getting in because the tubes on each side of the radiator matrix were not being covered with coolant when cornering and also, perhaps, from air trapped in vortices in the highly turbulent coolant in the header tank. I take Richard`s point about cylinder head gasket weakness but I don`t think that this applied in my case since the change to radiator No.4 solved all the problems. You can drive quite safely with the thermostat out and the by-pass either blocked or not blocked provided the thermometer reads less that 95 deg.C and you may find, as I did, that the cooling is better with the by-pass not blocked which seems to give a better pump performance. This is assuming that the thermometer is reading correctly - I seem to remember, from our earlier correspondence, that your thermometer readings were a bit suspect. All my radiators have been the same as those fitted to B270DA onwards and to the R Type - deep matrix with hole for starting handle in bottom tank, side mounted filler cap and with the steam valve containing a spring and a plunger with a hole down the middle. Is yours the same or different? B108CF would originally have had a radiator with a shorter matrix (starting handle going through below the bottom of the lower tank), a top mounted filler cap and neither a spring or a plunger in the steam valve. Bill Coburn doubts whether the small screw at the side of the thermostat pocket has any other purpose apart from locating the thermostat correctly. The answer is that it did also act as providing the air release hole opening (see Service Handbook) which is essential if the Bentley thermostat has no air release opening in the main thermostat valve itself. The early thermostats had no hole in the main valve but the later ones did. I agree entirely with Richard`s dictum not to try to unscrew this screw because it is almost certain to have rusted up. If your Bentley thermostat, when you get it, does not have a hole in the main valve then put a small drill through somewhere. The top of the thermostat has two blind recesses tapped 3BA to take extractor screws and I recommend that these recesses be drilled and tapped 3BA all the way through. This not only provides freedom from air locks but also give more thread engagement for the extracting screws. You ask about checking the size of the water pump pulley. The small pulley, with the small fan, was fitted to all cars prior to B1GT. B1GT onwards had a large pulley and a large fan. But some export cars had a small pulley and an intermediate size fan. B108CF would have started life with a small pulley and either the small fan or perhaps the intermediate sized fan according to where it was to go when new. But there may have been changes to B108CF over the years. The small pulley is 5 3/4 inch in diameter and the large one is 7 3/8 inch in diameter. The adapters which mount the various pulleys on to the pump shaft are different so the fans are not directly interchangeable. The standard small pulley sits behind the adapter and cannot be removed without removing the adapter whereas the large pulley sits in front of the adapter and will come off on it`s own. I have had to modify one of my small pulleys so that I can fit either a large fan or a small fan without taking the pump off. I don`t think that an electric fan is really a good idea on the MK VI. The only place it could go is in front of the radiator which is a difficult place to access and unless the fan is actually being driven it tends to obstruct the airflow. In your case there is the additional problem of providing the current to drive it since at present you only have the 4 1/2 in dynamo. The cooling problems on a Mk VI are usually mainly concerned with coolant flow. If the coolant flow is not OK then enhancements to air flow don`t seem to make much difference. But it would be worth while to see that the mixture is not too weak and that the ignition is not unduly retarded. Richard would probably know what are the correct carburettor needles to go with your oil bath air cleaner. I have prepared some photos of thermostats and pulleys to go with this post but I have had some problems in getting them up on to the website. I will try again later and if not successful I will send them to you by email. | |||
| Laurie Fox New User Username: laurie_fox Post Number: 5 Registered: 6-2004 |
Here are the photos to go with my recent post. Thermostat showing exit aperture to by-pass.  Thermostat showing location slot.  Thermostat(later type)showing small air vent valve in main valvehead.  Pump with small pulley. Rim of pulley roughly same distance from spindle as the upper casing bolts.  Pump with large pulley.  Pump with adapter for large pulley. Large pulley can be taken off without removing adapter.  | |||
| Bill Vatter Experienced User Username: bill_vatter Post Number: 8 Registered: 9-2004 |
Such a wealth of information on this topic; certainly the most thorough discussion I have seen on anything recently. Laurie, those are excellent photos and very explanatory. However, KC should not expect to get a thrermostat that looks like the one you picture. The pictured thermostat is the original type, which has a bellows filled with ethanol to make it work. The ethanol boils at something like 70C which expands the bellows and opens the thermostat. The stiffness of the bellows resists expansion somewhat, which results in rising pressure inside, which suppresses ethanol boiling, all of which result in the thermostat having a 10-15 C operating range, i.e., begin to open around 75C and fully open around 90C. Owners with original-type thermostats can diagnose faulty operation by shaking the thermostat while listening for the fluid internal to the bellows sloshing inside. If you hear no sloshing, the bellows has leaked out the ethanol. If you hear the sloshing, that indicates something else is wrong, like perhaps it is stuck from corrosion deposit. The calorstat on Silver Wraiths, which opens and closes the shutters, works on this same principal, and I have found that a leaky bellows can sometimes be soldered and the bellows then refilled through a siphon tube that is provided integral with a calorstat. That is a lot of work, but calorstats cost about $500 US. When Calorstats leak ethanol, they fail to a mid-position, neither fully open nor fully closed, and I would expect RR design philosophy would be the same for the water thermostat, i.e., when the car has trouble, it continues to keep going with diminished performance so that it's gentleman or lady owner is not left by the side of the road on a cold, rainy night waiting for the lorrie to come for them and the car. That type of ownership event would have been quite contrary to strong performance in the sales room, and the rarity of such events was a strong selling point for R-R cars from the very beginning. I said the replacement thermostat won't look the same as Laurie's. However current production thermostats should not require you to call for the lorrie either. Laurie, have you ever had to call for a lorrie? (Sorry, could not help my self. You now have a right to say something about my pouring in the gear oil if you wish.) Current production does not have a bellows but rather a bi-metalic piece like other modern thermostats. It will not be nearly as long, and you may wonder how can it be so expensive, something I have wondered about other R-R parts on occasion. However, the critical points of bypass operation, and the locating slot are still there, as well as the vent hole in the top. Current production thermostats are very stiff over their whole operating range, and the phenomenon of flow affecting thermostat position noted previously in this string will not be a problem. Regarding a head gasket. If that is causing a problem, other problems even more serious may be occurring also. Glycol is death to engine bearings, and if glycol is getting into the oil, you need to get it out now. Something else about glycol you should know is that while it suppresses boiling, it also transfers heat less readily. These two points should be reason to consider not using glycol. In my car I use straight water with corrosion inhibiting chemicals added. You might try this also if it turns out your radiator is marginal and you want to put off for awhile getting a replacement. Water seepage into your oil is not desirable, but it will not kill your bearings like glycol will certainly do if it is present in any significant quantity. My car is a Silver Wraith, and all early Silver Wraiths well into LWB series production have the early core without a bottom tank. However, overheating is not a problem, even though the heavier car puts greater heat load on the radiator. This is because the shutters, operated by the calorstat, open much wider than those of the Bentley. When they are fully opened, they are almost straight in line with the fore-aft direction, allowing maximum air flow. This set of facts suggests that Norman's idea of opening up the shutters on an early Bentley might indeed be a worthwhile consideration, not to be summarily dismissed. | |||
| KC Saayman Experienced User Username: kc_saayman Post Number: 6 Registered: 10-2004 |
I took the car for a slightly longer drive at midday in 30 deg temperature. I drove about 5 km at 60 mph, and the temperature never exceeded 80 deg, dropping to about 70 to 75 deg when I reduced speed to 40 or 50 mph (this with no thermostat, and the by-pass blocked) In stop / start traffic the temperature maintained 75 to 80 deg. Later that afternoon on my return journey in cooler weather the temperature remained at about 70 deg. It therefore looks like I may have solved the problem by flushing the engine and radiator. However, I would still like to have the radiator professionally cleaned in the not too distant future. Is it difficult to remove? Regards KC | |||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 388 Registered: 4-2003 |
With the thermostat removed, a healthy colling system will run at no more than 65degrees under the condizions you describe. Sorry, but I think you have only just started. Below are the steps for removing the radiator: R-Type and MkVI are the same in this regard.
The following may be of interest, written by an RREC member: ______________________________________________ Crud build up in the block causes boiling at hot spots around the bases of the cylinder bores. This may be confirmed by red silt staining the themostat. Not only is localised boiling undesirable, but it also releases bits of crud which quickly lead to a partially blocking of the radiator in almost every case. The final effect is that cooling becomes uncontrolled under sustained load such as highway cruising. So, the hots spots go unnoticed, but the resulting blocked radiator shows up as overheating. It is usually impossible to clean out the radiator when it is on the car as the tanks must be removed. Furthermore, a flow test is insufficient to show up anything but a really bad case of blockage. Localised boiling also puts steam into the system, and if there is enough around before it condenses, the system will take off, especially with a part-blocked radiator. Now for the cure. Remove the core plugs on most engines, but not on these engines as they have side plates. The side plates are real swines to remove as their retaining screws give all sorts of problems. Quicker is to remove the cylinder head, scrape away at the crud and muck with screwdrivers, and use a suction probe down through the top. Also useful is to remove the water pump and scrape through the opening. That is the main part, but now to finish the job after any repairs to a cooling system: Remove themostat, remove the lower part of the top hose. Now dont laugh: get an old pair of tights and cut the bottom foot off about 12'' then slide it up inside the top hose, connect the top hose locating the tights round the housing. Fill the cooling system and give the car a good long brisk run. After a few trips and when cool, remove the top hose and remove the [filter] tights. I am always amazed at the debris that is collected in the tights. As the radiator is almost certainly blocked, now is the time to remove it, and recore or mechanically clean it with rods. Then refit the themostat and refill the system with a good antifreeze. The car, in most cases, will be cured and will run cool. Check after a week or two that the coolant is clear. If not, there may be other problems such as a cracked or porous head or block. _____________________________________________ | |||
| Laurie Fox Experienced User Username: laurie_fox Post Number: 6 Registered: 6-2004 |
KC I think that the temperature readings you got from your latest run are quite encouraging. You will already have seen Richard`s notes about radiator removal, but there is an additional point and that is why I asked that you should let us know whether your radiator is the same as mine or not. The is because there have been two different types of radiator fitted to the MK VI, an early one which is shallower (top to bottom) where the starting handle passes underneath the lower radiator tank and a later one which is deeper and has a hole through the lower radiator tank to take the starting handle. Mine is of the later type - see photo below:-  The cradle in which the radiator rests is different as between these two radiators. B108CF would have had the early radiator to start with and may still have it. When you come to take your radiator out you will have to decide what you are going to put back and this may depend upon what reworking/replacement facilities are available in your part of the world. If you have your present radiator cleaned out or rebuilt with a new core then there is no problem either way but if you do go for a replacement radiator then I would expect that you will find that the deep type is easier to get than the shallow one and this may involve a cradle change. There is a dealers bulletin which details modifying the early cradle to the later one and also a bulletin giving rather more details about the removal of a radiator than in Richard`s notes. I can email copies of both of these to you if you wish. You may be getting confused about the different approaches and different remedies proposed by the folk who have contributed to this topic. This is largely because different people drive their cars in different ways and stress them differently. Their cars are also subject to different constraints (time and money) when being sorted out. Ultimately it is up to you to decide what to do with your own car and we shall all gain when you tell us about it. | |||
| KC Saayman Frequent User Username: kc_saayman Post Number: 16 Registered: 10-2004 |
Hi all Herewith a report back on my Mk VI overheating problem. The 73 deg thermostat finally arrived from the UK. I flushed the engine and radiator again , installed the thermostat, and the car now runs at just below 75 deg in normal conditions. Thank you very much for all the help! Kind regards KC |
