| Author | Message | ||
     Ron Lewis New User Username: great48 Post Number: 4 Registered: 1-2009 |
I am a bit concerned about the engine coolant temperature of my Mark VI (B146BH) when stuck in traffic on hot (Aust) days. It hasn’t reached boiling point yet, but it comes very close to it (90-95°). I’m told that higher than normal coolant temperatures in stop/start traffic aren’t unusual for this model, but I would prefer to be occasionally looking at the temperature gauge, rather than the gauge putting me under its hypnotic spell every time the traffic grinds to a halt. The radiator had a full clean 7 months ago (tank removal, detergent clean, all core passages rod cleaned, etc.). A good quality anti-freeze was added at the prescribed dosage, as per the manual (I have a further question on this later in the thread). Don’t know if any flushing of the motor was done at the time (either minor [reverse flush] or more major internal inspection and cleaning) but I would prefer not to go into major cleaning work if I can avoid it, as the motor is currently running fine. Talking to a friend who is a member of a British sports car club, he advised a number of their members had similar overheating problems, even after overhauling the cooling system. He says they solved this problem by fitting an electric water pump into the lower radiator hose (i.e. remove approximately 4 inches from the centre section of the radiator hose and fit the pump there). The pump manufacturer (a prominent player in the engine cooling industry) advises the unit will pump 80 litres per minute, and can either be used in addition to the engine’s original water pump, or as a stand alone unit, after the original pump has been removed. According to the marketing information, the pump can either operate automatically, based on engine temperatures (obviously only after “full open” thermostat temperature has been reached) or it can work through a manual on/off switch operated by the driver. I would be looking at using the electric unit in conjunction with engine’s original pump, and probably operating it manually when traffic snags are encountered. I remember reading somewhere about the sediment build up around the cylinder castings of the 4.25 litre block and the difficulty of removing this after it hardens. One thought I had is that maybe the extra pump could help to slow down the process of accumulated sediment turning into a hardened crust by the higher flow volume (of the additional pump) keeping the looser stuff suspended in the coolant, making it easier to remove when the time comes round for routine flushing of the engine. A couple of questions I would like forum feedback on are as follows: 1. As the cooling system runs on atmospheric pressure, will the pressure created by the new pump (pumping 80 L/min) cause any problems with the cooling system or the heater core? (I assume a small level of pressure will be created). The heater core got a mention, as I’ve heard they are a little on the frail side on the Mark VI. 2. What inhibitors should I be adding in addition to the glycol? 3. Are the radiator hoses available as off-the-shelf items in Australia? If so, would appreciate part numbers and source. Looking forward to any help/comments the forum members can provide. Ron Lewis | ||
| David Gore Moderator Username: david_gore Post Number: 866 Registered: 4-2003 |
Hi Ron, Have sent you a personal message. Regards David | ||
| KC Saayman Frequent User Username: kc_saayman Post Number: 83 Registered: 10-2004 |
Hi Ron I had a very similar experience with B108CF. After cleaning the radiator the engine still overheated in traffic and especially at high speeds or long up-hill runs. A friend of mine who works on WO Bentley’s solved my problem. The engine needed a really decent flush, and as you noted, a normal backwash simply does not remove all the dirt in there. By putting together a few garden irrigation fittings he devised a contraption that allows one to connect an air compressor to a normal hose pipe. We then disconnected the radiator hoses and removed the thermostat. Also, very importantly, remove the tap near the rear of the engine (not just open it, remove the whole thing) The engine is then filled with water via the bottom inlet, and once it runs out the top you give it a burst of air. This causes the water in the engine to build up pressure and “tumble”, almost like inside a washing machine. Then wait for the engine to fill up with water again, and give it another burst. This is repeated until the water that comes out of the top is clean. You won’t believe the amount of rubbish that is removed from the engine using this method. I cleaned the radiator in the same way. My car never again overheated after this, and I now give all my cars this treatment on an annual basis. I can post a photograph of the contraption if anyone is interested. My friend’s name is Watson, so I call this method the Watson Flush. Kind Regards KC | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 285 Registered: 6-2006 |
Ron, in addition to KC's suggestion - which sounds like a good tip. There are three round plates on the right hand side of the engine. These access the water ways around the cylinders. Remove these and blast out any silt you find with a pressure washer. Then do reverse and forward flushing. On a bad engine you can end up with a bucket of silt. This is usually enough to get water flowing again, without the need for electric pumps or fans. | ||
| Bill Coburn Moderator Username: bill_coburn Post Number: 1083 Registered: 4-2003 |
Perhaps relevant but a warning to vee eight owners. Avoid the compressed air flush of these engines I have seen two cars have their lower 'O' rings on the cylinder barrels blown. One we fixed with Barrs leaks the other required complete dismantling and rebuild - 145 hours work! | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1604 Registered: 4-2003 |
Bill, likewise on the early postwar motors. The water pump seal on all but the very last R-Types (B160YD) has a rubberish boot around the carbon sealing gland. It is normally at atmospheric pressure plus water head and a bit of flow resistance pressure. Any pressurisation in the system may blow it out if it is at all weak. Oh well, at least it would be an early failure of a weak boot on test rather than on the road. Crewe had all sorts of problems when the early cars ran pressurised before they were all modified to run on atmospheric pressure, and that was not only related to the water pumps. As to opening the water jacket covers, good luck mate. The setscrews usually shear off on a pristine motor, let alone on one in a rusty state. Usually, they are only safe to remove with the block on a bench and with a driver press. You may just be lucky with a really good impact driver if you can swing a hammer down there. There's not much room for a drill down there to clean out the threads to tap them oversised either. It's all rather tempting fate. Now, does that thermostat have a proper bypass valve ? If not, it is the surest way to make those motors overheat in traffic. As to electric pumps and fans: global warming can't be so bad yet that the cooling needs of a motor with excess cooling capacity have changed in 60 years. These motors never had inherent cooling problems other than running too cool at speed for the pistons. Mind you, if the thermostat has no bypass valve, an in-hose electric pump may make up for it. It may be a cheap solution instead of a proper thermostat, but take your chances. Hoses ? Here are a few examples: Morris Minor top hose for the bypass, FX-EK Holden for the top hose, shortened 2" to fit, and FE-EK Holden for the lower hose. Many others will fit, and most spares chains offer generics and universals. Try Repco and Autobarn. They all fit, but lack the external fabric covering and bellows. Reinforced garden hose is by far the best for the heater hoses. It lasts forever, and doesn't rot with heat or oil. RT. | ||
| Martin Cutler Prolific User Username: martin_cutler Post Number: 107 Registered: 7-2007 |
I have had years of problems with B256MD, have done all the above things, compressed air, etc, have gotten bucket loads of muck out of the system, and my car now runs cool, even on a 42 degree day. 2 things I would add to all the above: 1 - fit an in-line filter to the top hose. I clean mine out after every run, still collecting muck almost every time. 2 - fit a smaller fan pulley, this turns the water pump faster, and I haven't noticed increased fan noise, which is about the only drawback. This is the modification which has by far improved the traffic standstill issue. It will sit on 75 degrees all day now, no problems. I had a run of 6 pulleys made last year, and they have all gone onto cars except the one I have for my R type resto project. If you need one to copy, let me know. I'm in Sydney. I also know a very good machinist who can turn you one up. Cheers Marty | ||
| Stephe Boddice Frequent User Username: stephe_boddice Post Number: 68 Registered: 2-2005 |
75ºC sounds about 10 or 15 degrees too low to run one of these engines. | ||
| Martin Cutler Prolific User Username: martin_cutler Post Number: 108 Registered: 7-2007 |
Hi Stephe, As far as I know, 75 is where the thermostat opens on both my MK VI's. V8's with pressurised systems have 88 degree thermostats, is that what you're thinking of? Marty | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1606 Registered: 4-2003 |
Although this doesn't apply so severely to a motor once it has covered 10,000 miles or so, below are graphic illustrations of what can happen when running at temperatures too low. Best run as warm as the thermostat allows without temperature runaway, and that is maybe at a true (the temperature gauge may read something different) 85C or a bit higher for an unpressurised motor, or at 95C or higher pressurised. A motor with a decent mileage is less at risk of failure, but piston wear is greatly increased with cool running nevertheless. It also explains why engine wear is dramatically increased while the motor warms up. I have seen it three times on 4 ½s , once on my own R-Type after I assembled it with new full-length liners and new standard-bore solid-skirt Repco injection diecast pistons and gave it a healthy blast after 500 miles. The others were on motors newly precision-overhauled at great expense by professionals with JP split-skirt pistons to standard bore. One was with 1,000 miles after a rebuild just a few years ago. As an insurance, I had the replacement pistons made to run with a larger bore clearance and tin plated as a further good measure. Of course, the tin is only there for the first few thousand miles before it disappears, Piston numbers 5 and 6 are most at risk, hence my scepticism at claims that the rear cylinders lack cooling. Also, thin oil is a killer. Apart from other damage, it restricts the spray from the conrod jets to the thrust sides of the bores. Conrods installed back-to-front would have the same effect at any mileage, also any motor with a faulty thermostat. 20W50 is definitely a no-go. Best is to use a 5W50 fully-synthetic oil in hot climates on a motor with a low-speed oil pressure deficiency, or to use a 0W30 synthetic anywhere. R. L/B Silver Dawn pistons.   | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 289 Registered: 6-2006 |
I've never had problems removing the side plates. Only use Snap-on screwdrivers, impact driver bits. Lightly tap the screws/driver a few times to wake them up. The plates at the back of the head and block – now they are a different kettle of fish  Just my personal experience. I don't think you'll get as much sludge out through the drain tap. I suppose start on one that you can access in case you do need to tap it out. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1607 Registered: 4-2003 |
I don't buy it. Mind you, the plate at the back of the block is a snip by comparison. My roadside experience on that one when it burst 10 miles from Marulan, a hitchhike to the ANU to make a new one, the train and a hitch back to the car, to fit it, to fill from the creek and to drive to Sydney U by midnight proves it. It came off with a spanner. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1609 Registered: 4-2003 |
ps: maybe always using the correct coolant has one drawback, and shags the side cover threads by penetrating them for 55 years. At least there is no sludge in the cooling system. | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 290 Registered: 6-2006 |
Maybe it's something to do with the Australian magnetic field. Mind you it does remind me of the time I was rushing to the hospital to stand in for a surgeon client of mine that was supposed to be doing a brain transplant. I was travelling along the heads of the valley road in 4 foot of snow. Suddenly a side plate burst - or at least I thought it had. When I looked it was actually the block. Frantically trying to get to the operating theatre - I managed to borrow a pit pony from a local coal mine owner and gallop to the local steel works. I then borrowed a little of their equipment and cast a new block. Luckily I had a sufficient tool kit in the boot to machine it as necessary and rebuild it using the crank and pistons etc from the old engine. Fortunately I got to the hospital in time to do the transplant(which was successful) and finished in time to get the Pit Pony back before the morning shift. I now carry a tarpaulin in the boot at all times - Just in case. Them Ponies can't half S**T! It made a real mess on the back seat. | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 291 Registered: 6-2006 |
PS Ron – perhaps if you could borrow Richards spanner that can undo the (most likely) seized countersunk screws in the back of your block and head in a 3" gap - you could flush through there instead! To see what you want to avoid http://everythingrollsroyce.com/only_done_x_miles_this_year!.htm And have you looked at http://www.kda132.com/Technical/SectionB/cylinderblocks/cylinder 01.html | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 292 Registered: 6-2006 |
PPS those links haven't come out correctly, you'll need to copy the whole addy. | ||
| Bill Coburn Moderator Username: bill_coburn Post Number: 1084 Registered: 4-2003 |
Paul/ I think you won that round. Reminds me of a guy I knew who claimed he did everything the hard way and if you stood still long enough he would regale you with the detail. But he almost met his match when an exasperated listener retorted, 'I bet you don't do one thing the hard way'. "I know what you talking about said the fellow and I do". "I can't believe it said the other - how?". "Why standing up in a hammock" was the reply! | ||
| Martin Cutler Prolific User Username: martin_cutler Post Number: 109 Registered: 7-2007 |
Hi Richard, You lost me there a bit. You say thin oil is a killer, then recommend fancy pants synthetic oil at 0w30, might work well in -40C in Europe. I use 25w70, which is the equivalent of the old 40 weight oil. Did some work on a Dawn, heated the heads of the countersunk screws with the oxy, they all came out OK. Undid the tap from the back, got HEAPS of crud out using compressed air and water. Fitted a small diameter pulley, car is much better behaved now. It is going to Albany for the Federal Rally. Cheers Marty | ||
| Ron Lewis New User Username: great48 Post Number: 5 Registered: 1-2009 |
Thanks, all - great response. Some good warnings and advice for the unwary, plus some great tips (and humour) as well. Certainly quite a bit to mull over before reaching for the tools (or tossing the coin to decide which way to go). Never thought I'd need a frontal lobotomy after attempting a simple engine flush, but could after trying this one. Hope Paul's still got his surgical instruments handy!! And thanks Richard for the hose information. Regards, Ron Lewis | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1612 Registered: 4-2003 |
LB Silver Dawn pistons. Cold running. Overweight oil. A new subject on oils is due.   | ||
| Martin Cutler Prolific User Username: martin_cutler Post Number: 110 Registered: 7-2007 |
Hi Richard, Interesting photos. If that piston had come out of my air cooled motorcycle, I would have said it had got hot and nipped up. When you say cold running, how cold? Did the thermostat keep it at 75 degrees C? As you probably remember, I worked for Penrite Oils for a couple of years, I'm working as a mechanic now, but it was very interesting working for an oil company, learnt lots of things. The main issue with thick vs thin oil in our 60 year old cars is getting it to the top of the motor when it is cold. If it is cold, as in European cold winter, then a thick oil is a problem. The viscosity of a 5W50 at operating temperature IS NOT the same viscosity as a 20w50, nowhere near it, even though they both say 50 for operating temperature. Did an oil change on a Phantom 1 the other day, fellow complained that it was leaking oil everywhere. They had put hypoid 80/90 in the diff and gearbox - you could hardly hear yourself think while driving it. Some straight 250 weight later, and things had settled down. Cheers Marty | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1613 Registered: 4-2003 |
Hypoid 80/90 in the gearbox indeed. My, some Phantom blokes may have a word to say about that. Agreed, Canberra is cold sometimes, and hot sometimes as well. | ||
| Neville Davies Experienced User Username: nev_davies Post Number: 18 Registered: 9-2006 |
Martin. Could you explain the grade of oil that is 250 weight please?I've ep90 in my spirit I think. Nev | ||
| Martin Cutler Prolific User Username: martin_cutler Post Number: 111 Registered: 7-2007 |
Hi Neville, yes, in a Silver Spirit diff, Extreme Pressure 90 is correct, however, in a 1929 Phantom 1, it tends to fall out onto the floor. The heaviest oil you used to be able to buy was 600 weight, or steam engine oil. My 1925 Dodge gearbox calls for 600 weight, but it gets 250 now. I was told I could mix in a bit of grease, but it seems to shift OK with the 250. Out of interest, the viscosity scales for engine oil and gear oil are different, so a 40 weight engine oil is a different viscosity to a 40 weight gear oil. Hi Richard, I pulled out my ACL Piston failure book today, and they do have a picture of a piston which has failed due to cold running, and it didn't look like your pistons. Was it over-revved whilst the engine was still cold? Still looks like a hot piston nip up to me. cheers Marty | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 804 Registered: 9-2004 |
Heat siezed it is Marty.you are correct,any engineer will confirm the piston illustrated has heat siezed. Another example is shown below, this was due to an overheating problem due to water flow restriction on just one cylinder of a particular engine.  | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 295 Registered: 6-2006 |
Doesn't look like normal cold seizure or lack of lube markings to me, but then they are strange beasts! Maybe the engine was 65 on the temperature gauge (at the front of the engine) but the rear of the engine was cooking? On the engine in my photos above, The rear of the head / block reached 110 c in less than 5 mins.( I didn't have the gonads to run it for longer) Front of engine was 40. Measured by IR thermometer on the block and head. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1625 Registered: 4-2003 |
Heat seized it was. You may also call it cold seizure if you wish. The piston ran hot in a bore too cold. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1626 Registered: 4-2003 |
I really must take issue here. The piston picture posted earlier is a classic victim of so-called cold seizure. The motor of the Silver Dawn was doing fine at a leisurely highway pace soon after overhaul. Unfortunately, it was running a heavy oil in mid winter. It was snowing at the time. Suddenly, the piston gave way as shown. It all ended up in successful litigation as the cause was proven with the blessing of the technical authorities. The cornerstones of the case were the wrong thermostat, the heavy oil, and insufficient bore clearances. Most familiar with these possibilities are those in the aircraft and Skidoo businesses, namely Bombardier and Yamaha. Their motors are subjected to sudden temperature extremes, and of course to cold running much more than any motorcar usually encounters. Air-cooled motors are the ones in need of the closest attention to design. Below is a picture of a Rotax engine seizure, again a classic case where the cylinders were too cool and the piston at normal running temperature. The main issue is that a piston warms and expands very quickly on a cold start, and the block lags in temperature. As MkVI blocks are renowned for cool running at all times, there is a definite consideration to make. A heavy oil does no good either, especially on a young motor. It is a subject covered by the IHS. You my even read about it in the United Kingdom Air Accidents Investigation Branch bulletins. Below is an extract. Just because some authority wrote it down is no guarantee of correctness, but this time it all does make sense. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< United Kingdom Air Accidents Investigation Branch AAIB Bulletin No: 11/96 First the term Cold Seizure is a bit of a misnomer. All seizures are caused by heat/friction. A cold seizure is where the piston expands faster than the bore it is travelling in and contacts the sides of that bore. These are also known as four corner seizures. The worst-case scenario is that the engine can just lose power and stop. In the case of a mild (mini) seizure the engine may just lose power for a second or two, but will respond to throttle inputs and will recover when the throttle is advanced. This may happen a few times before a major seizure occurs.  | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 807 Registered: 9-2004 |
Rt,look at the piston rings, together with the piston damage this is a common cause of heat seizure. Hard to be incorrect never mind. This is now confirmed in a recently ovehauled engine. The mind boggles what the driver was doing to let this occure with the damage so bad. The piston seizure damage in my picture was confirmed by local heating of one cylinder and was curable by water flow modification to the problem. This was not a overhauled engine but one that had done a high milage! | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 296 Registered: 6-2006 |
Wondering how to tell the difference between a cold / 4 corner seizure and a hot seizure? The 4 corner seizure , strangely enough, seize on the four corners. (4 corners on a round piston! Clever stuff ay?) They seize in a pattern of 4 vertical scuffs on the pistons. A hot seizure is much more widespread and wipes a large amount or all of the circumference. | ||
| David Gore Moderator Username: david_gore Post Number: 873 Registered: 4-2003 |
"The 4 corner seizure , strangely enough, seize on the four corners. (4 corners on a round piston! Clever stuff ay?) They seize in a pattern of 4 vertical scuffs on the pistons." Richard, Paul & Pat - this is interesting from a technical point of view..... Is the damage in the same place on the piston skirt each time you have observed damage of this type? Is there any correlation between the thickness of the metal/presence of cooling passages in the engine block adjacent to the points of metal-to-metal contact? | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 297 Registered: 6-2006 |
Hi David, I've never come across cold seizure on a R-R or Bentley engine. On bike engines , I think it's where the piston webs expand pushing the skirt out onto the cylinder walls. It's usually a very cold engine being revved too high, too soon. It's the piston heating and expanding that causes the problem. | ||
| AnthonyTan Unregistered guest Posted From: 114.77.137.87 |
Hi guys , Wondering if anyone can help, I’ve had my engine rebuilt on my mark vi Bentley 4/2.5 Engine is running hot Its got no thermostat , radiator has been professional cleaned, rebuilt water pump by specialist, block clean when rebuilt, new radiator hoses It’s running at about 190-200 degrees, I’ve noticed it gets hot after 5 minutes of running, the front grill gets hot to touch also Do you think I need to install a thermostat to low the temperature Also would installing a electric thermo fan behind the front grill will help the cooling or putting a smaller pull on the water pump is better? Thanks in advance Regards Anthony (Message approved by david_gore) | ||
| David Hughes Experienced User Username: wedcar Post Number: 109 Registered: 07-2004 |
Anthony Initial start up after overhaul often neglect to eliminate/ expel air from the cooling system. Also it is essential to fit the correct thermostat to these engines, apart from any other issues you may have, the correct thermostat blocks off the radiator bypass circuit, ensuring all coolant goes through the radiator. Regards David | ||
| Christopher Carnley Unregistered guest Posted From: 109.156.10.116 |
Retarded ignition makes the engine boil along with too tight a piston/ring fit. Thermostat essential. (Message approved by david_gore) | ||
| Bill Vatter Experienced User Username: bill_vatter Post Number: 92 Registered: 09-2004 |
As Chris said, put in a correct thermostat. A lot of people are unaware that without a thermostat a significant amount of hot coolant goes through the bypass without being cooled. When the thermostat fully opens the path to the radiator, it simultaneously closes the bypass and vice versa. The water pump has a small vent, internal within the enging coolant space, that allows air that would otherwise be trapped in the pump to escape and eventually travel to the upper radiator tank. Air in the pump will prevent proper pump operation. The internal vent mentioned can become blocked by corrosion deposits. You did clean all of that out when you overhauled the engine, didn't you? | ||
| Jeff Martin New User Username: jeff_r_1 Post Number: 23 Registered: 07-2018 |
I run the warmer thermostat all year round in mine. The car runs and idles better too. I actually have some descent heat in the fall when the weather starts to freeze. If the car is healthy and things are set right, running a warmer thermostat is better for the engine over-all. https://www.introcar.co.uk/thermostat-88-degree-p3778 |
