| Author | Message | ||
     Charlie J Unregistered guest Posted From: 68.212.35.27 |
I have had remarkable success with your suggestions thus far and should have listened to you folks before embarking on my own preconceived solutions. However, this time I am truly in a serious predicament. My Corniche overheated due to a melted heater hose and subsequently has pressure in the radiator(which has been checked out of the car). I replaced the radiator cap and the seal under it thinking that it was leaking due to age. After a lot of head scratching I placed the overflow tube from the radiator tank into a bottle of water. Bubbles were produced from the hose. Evidently (to my untrained mind at least) there was a pressure build up coming from the engine. My guess is a head gasket problem but I would appreciate a 2nd, 3rd, 4th opinion. I must admit I used a radiator stop leak product which has to date not worked since after only 5 or so miles the coolant level light comes on indicating a loss of coolant. (I have checked all hoses etc. and there are no leaks while running save the overflow tube). (Message approved by david_gore) | ||
| David Gore Moderator Username: david_gore Post Number: 797 Registered: 4-2003 |
Charlie, Is there any sign of water in the engine oil? Is there any sign of oil floating on top of the radiator coolant after you refill the radiator, idle the engine with the filler cap removed for a few minutes then let it stand for an hour or two? Suggest you flush the entire system several times to remove the radiator stop leak - these cause more problems than they fix in my opinion. | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 154 Registered: 6-2006 |
I'd Agree with David, get it flushed out first though. Take the car to a garage with an exhaust gas analyser and get them to test the bubbles for exhaust gases. You may need to make a tube to stop the gases blowing away. ( bit of plastic pipe ) Don't let the probe go near the water though!!!! Have you got a black header tank or plastic? Black tanks have a separate steam valve that can leak. If the gasket is gone between the cylinder and waterway, It will pressurise the cooling system quickly (often without overheating) and without tell tales like water in the oil and visa versa. | ||
| Charlie J Unregistered guest Posted From: 74.164.165.192 |
I forgot to mention there is no oil in the radiator fluid nor water in the oil. The tank is metal and mounted on top of and separate from the radiator. The engine doesn't begin to overheat until the water is blown out of the rad. (Message approved by david_gore) | ||
| David Gore Moderator Username: david_gore Post Number: 798 Registered: 4-2003 |
Sounds like a compression leak to me so Paul's suggestion re using the exhaust gas analyser would be the next step. If you have a good nose, you might be able to repeat your test with the overfow tube and smell the escaping gas. If this test is positive, you will have to face the decision about whether you try to remove the heads yourself or hand the responsibility on to a profesional. This decision will depend on the past history of the car with regard to preventative maintenance [a "bust & fix" history suggests the use of a professional will save more than what it will cost], your experience, ability and workshop facilities. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 768 Registered: 9-2004 |
If the sniffer test or useing the emission tester prove ok then best to do a reverse flush on the radiator. If ok check that the thermostat is in place. If problem still exists then carry out a leak down test. This will point to problem to the cylinder at fault under load or a crack that opens up! Laser temp gun can also be of use to pin point the problem area. May not be in the manuals or a method that the old crew use. | ||
| Charlie J Unregistered guest Posted From: 68.212.35.27 |
It would be fine to determine which cylinder was leaking but wouldn't I have to remove the head to fix the problem? Are there any other possibilities beside the leaking head gasket or cracked valve seat, head or block that could be fixed without removal of the heads. Another question; once one head is off is it recommended to regrind the valves on both heads. Also should the head be warped how much can the head be re-surfaced (shaved). (Message approved by david_gore) | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 155 Registered: 6-2006 |
Charlie, Determining which head was doing it MIGHT mean you would only need to take one head off. Disconnecting Spark plug leads one by one can also narrow down the area to search. I was always taught to do both at the same time and skim both heads the same amount , but I guess that may be old school because I've stripped engines with one new and one old gasket on. Hmmmmmm or maybe that's WHY I'm having to strip it?  If it has gone due to overheating, I'd certainly do both. Yes DEFINITELY have the head skimmed. It will not be warped enough to stop you skimming it ( IMHO ) Yes get the valves lapped at least and ground and lapped if unnecessary. Don't be tempted to do it by hand unless you have plenty of excess time and energy - they are very hard! Fit new valve stem seals. Find out if it IS exhaust gas or steam! Temperature is the main key here, Is the water boiling and making steam bubbles or is it exhaust gas? If the cooling system is full, the heater tap is open and heater system is also full, there should be no way for air to be pumped out of the cooling system. Especially if the water is relatively cool ( nowhere near boiling point ) You will always get a few bubbles as the water goes from cold to hot. But that should be all. You should make sure that The radiator is clear. The steam valve is working. The thermostat is out.(while testing) The heater tap is opening. The heater matrix is clear. Fan coupling is working. You have let any air trapped in the water settle and escape. ( high pressure hoses/ combi boiler water is often cloudy until the air escapes) etc etc etc . . . . . But none of it will help if it is exhaust gas! | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1387 Registered: 4-2003 |
I'm afraid that I cannot agree on musch of the above. 1. Do not run the engine again, nor turn it over without removing the spark plugs. Reason: if the head gasket has blown. then coolant may leak ino a bore. If that cylinder is on its firing cycle, the imcompressible coolant may cause enough blockage to bend a conrod. Disaster. I have seen this on a Silver Shadow at Yorks. 2. Never skim this type of cylinder head unless absolutely necessary. Have the mating surface polished and precision measured, and only resort to skimming if there is a real need. Reason: these heads may be skimmed only twice then they are scrap. Too much skimming puts the valves too cliose to the pistons, the head will not fit properly and more awfuls apply too. 3. Do not hand lap the valves. If a valve has a bad face, replace it and have the seat cycloground to fit the valve exactly. Reason: the stellite faces are too thin to grind, and hand lapping went out 30 years ago anyhow. 4. Best do both heads as if one gasket has blown then the other may do so soon too. The extra work to do both is only about 20% more. 5. By all means do a pressure test on the cooling system. Pump it to 22 psi and let it leak down a few times. With the plugs removed you may crank the engine. The plug hole which spits out coolant will give you a lead on the source of the leak. It's not a job for someone who does not know these engines extremely well. RT. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1388 Registered: 4-2003 |
ps head cracks are repairable by an expert shop. RT. | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 157 Registered: 6-2006 |
Charlie, Have you found out what the gas it yet? Don't get to frightened by some things you read. Just make sure that you take good advice. If you do have to take the heads off, take them to a reputable engineering shop. As long as you don't go in and act like an arse telling them how to do their job, they will just take the minimum off to get the head flat which will usually be next to nothing on the R-R V8 heads. A good shop will start at zero and go from there. You can try pumping up the cooling system but as the cylinder gasses are about 30 times higher and you're only getting a little gas through, it may not show anything. Careful if your radiator and heater matrix are suspect though. Find out what the gas is first though | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 769 Registered: 9-2004 |
At this stage do not pressurize the cooling system. As Paul stated, first use an emission tester,I prefer a sniffer due to a bad experience with the emission tester taking a dose of water with a sudden blow back. Remember a pressure test on the cooling system is NOT a leak down test. A leak down tester uses air from a compressor and measures the rate at which it leaks through the engine. This is done with the engine not running and the beauty of this is that toy can find the source of the leakage by listening for the escaped air. Internal leakge is found by air bubbles in the cooling system. Tools needed are a leakdown tester, and an air compressor. Compressor should be at least 2hp and deliver 90psi. Procedure: Remove spark plugs. Set engine to TDC #1. Calibrate test gauge per the instructions. Lock engine so it can not turn. Connect hose to spark plug hole, Connect pressurized gauge to hose connection. remove radiator cap. If coolant sprays out, you have a head gasket etc problem. Do same test on rest of cylinders. Remember to set TDC of each piston for compression stroke in turn. This test is also great for head leaks and valve problems. Note that all engines will have some leakge past the rings. I always do full pressure test when I suspect a problem. Make sure engine is locked with full pressure test. (Message edited by pat lockyer on 26 May 2008) | ||
| Charlie J Unregistered guest Posted From: 68.212.52.14 |
I am going into the shop tomorrow. I will first attempt to locate a sniffer. If I can't find one I will pressure up the cylinders one by one with an air compressor set at 90 lbs. I have drained the coolant so I will refill and check for a leaky cyl. If none then I will pressure up the cooling syst. and with plugs removed check for water in one or more cylinders. I will report the results. At any rate there are reputable engine shops around and I intend, if it is a leaking cylinder to remove both heads and have them checked for warpage and have the valves/seats reworked/replaced where necessary. I will keep you posted. Does this sound like a decent plan? (Message approved by david_gore) | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 770 Registered: 9-2004 |
Yes,You will need a whistle to determin when each tested cylinder is set just before TDC. The other is the made up tool for locking the crankshaft,when the cylinder is under pressure it will try to turn the engine. May pay to do a search as I have a feeling that I may have covered this before. David or Bill your help needed! | ||
| David Gore Moderator Username: david_gore Post Number: 799 Registered: 4-2003 |
Hi Pat, Have just spent several hours searching the forum archives for the tool with no success. I recall seeing an item about a crankshaft locking tool some time ago however it may have been on another forum, in "Tee One Topics" or "Crewe'd Jottings". I think it was in an article about head gasket problems. Bill, looks like we are looking to you to save the day once again  | ||
| paulyorke Unregistered guest Posted From: 89.234.124.169 |
Any garage with a gas analyser should be able to do it. Get a piece of plastic pipe that will fit againt or into the radiator cap seal. The other option is a Head leakage chemical test. google sykes pickavant or snap on. it's a tube that is filled with a liquid that changes colour if exhaust gases are present. IMHO you'll be doing lots of unnecessary work checking each cylinder etc. The amount of gas you are getting at about 750 psi(?) is minimal so at 90 air or 25 water you'll be lucky to get much of a sign. Find out what the gas is , if it's exhaust gas, your plan sounds perfect. Good luck! (Message approved by david_gore) | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 771 Registered: 9-2004 |
David thanks for looking as I had no luck,I thought I may have put some pictures up of the leakdown test,will put some up on our next use of the equipment. Paul you say "The other option is a Head leakage chemical test". This is what we call the sniffer and would be my first choice, only ever given an incorrect reading once, that was on a diesel Mazda Bongo,what a cooling system when a problem accurs. Thats another story that I would like to forget. IMO sniffer is best [the emissions combie unit is to expensive to chance a blow back] then next is the leakdown test,we have a few shortcuts to make this a quick test. | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 160 Registered: 6-2006 |
Hi Pat, never heard it called a sniffer, sorry. I'd agree with you about the dangers and the 'sniffer' never being wrong - as a positive test will definitely mean exhaust gas is present. However, a negative test or iffy test doesn't always mean there's not. A gas analyser will pick lower levels of gas especially on new "clean running" engines. ( not an issue on your car ) Get a sniffer test done first, then a gas analyser if it's negative or you're in doubt. You can always drain a few pints out to help prevent blow back. | ||
| Charlie J Unregistered guest Posted From: 65.1.67.25 |
I have taken off both heads. I decided that knowing which cylinder was leaking was not that important since once you go thru the trouble removing everything to get to one head you might as well remove both. I am having both heads checked and surfaced if necessary along with lapping or grinding the valves also if needed.(All done by a reputable specialty shop). I found the telltale signs of a blown head gasket on the driver's side, third from the rear. (The circular mark from the head gasket had a gap as shown on the block surface next to a water passage). The cylinders still showed hone marks by the way. (A good sign I hope) I buffed the block surface, ran a thread die on the head studs, decarbonized the piston tops and wiped the cylinder walls with an oily wrag. One cylinder (the rearmost on the driver's side did not have any carbon buildup. In fact it was only coated with a thin oily film. Do you fellows think the spark was missing from that cylinder or perhaps an injector was clogged. It must have run like that for a long time because the rest of the pistons had considerable carbon that had to be removed with an air powered steel brush. Also was the fuel mixture too rich causing the carbonization (67,000 mi. yr. 1983) or is that natural. (Message approved by david_gore) |
