cookci Posted March 20, 2007 Share Posted March 20, 2007 as my car had been using coolant and blowing off exhaust gases through the radiator cap ive had the head pulled off! the head apparently shows no signs of over heating! Its turned out the HG has not failed and the head has not warped does this mean the head is cracked and not be visible? the engine shop fixing my engine are confused! please help! Quote Link to comment Share on other sites More sharing options...
Jake Posted March 20, 2007 Share Posted March 20, 2007 Are you saying that after taking the head off they found that the head gasket hadn't gone after all? That makes no sense to me Quote Link to comment Share on other sites More sharing options...
cookci Posted March 20, 2007 Author Share Posted March 20, 2007 yes thats what im saying Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 20, 2007 Share Posted March 20, 2007 The only other way your going to get the same symptoms is if there is a crack either in the head or cylinder wall (unlikely) and a water gallery. Quote Link to comment Share on other sites More sharing options...
cookci Posted March 20, 2007 Author Share Posted March 20, 2007 can these head gaskets "seap" with almost no visible evidence? this is the mechanics other theory? Quote Link to comment Share on other sites More sharing options...
Thorin Posted March 20, 2007 Share Posted March 20, 2007 Knackered rad cap? Quote Link to comment Share on other sites More sharing options...
cookci Posted March 20, 2007 Author Share Posted March 20, 2007 working rad cap lol Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 20, 2007 Share Posted March 20, 2007 Get the head crack tested. Quote Link to comment Share on other sites More sharing options...
letmeshowyou Posted March 20, 2007 Share Posted March 20, 2007 yeah get the head pressure tested. Anyone decent should be able to do that for you! Quote Link to comment Share on other sites More sharing options...
Kranz Posted March 20, 2007 Share Posted March 20, 2007 can these head gaskets "seap" with almost no visible evidence? this is the mechanics other theory? They can, but normally there is a mark left on the gasket where the high temperature gas has gone under it and burned it. As Dick (Tricky-Ricky) says get it pressure crack tested. As its already off its well worth doing. Prior to taking the head off they should have done a nitrogen pressure test, but not many places have the kit for this. If the head is not cracked it may be worth getting it skimmed to make it perfectly flat, to ensure there are no HG faliures in the future. Not having much luck are you mate? Quote Link to comment Share on other sites More sharing options...
cookci Posted March 20, 2007 Author Share Posted March 20, 2007 seems not no ive told him to do a pressure test whatever happens now he reckons the head is perfectly flat and doesnt need skimming! is it worth him skimming it anyway as he has the machine? Quote Link to comment Share on other sites More sharing options...
i-macca Posted March 20, 2007 Share Posted March 20, 2007 No, only get it skimmed if it's not flat. Otherwise just make sure the surface is very clean (possibly get it lightly resurfaced but don't take any meat off it). Needs pressure testing though, definitely. Quote Link to comment Share on other sites More sharing options...
TLicense Posted March 20, 2007 Share Posted March 20, 2007 ARe you 100% sure you were getting exhaust gas in the coolant? If not it could be micro-fractures in the plastic radiator end tanks. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted March 20, 2007 Share Posted March 20, 2007 Problem with pressure testing heads is the cracks often do not not open up and start leaking until the head is up to working temp, and it's not possible to duplicate 900 degree exhaust gasses through the ports and 100 degree water temps whilst it's clamped to a rubber covered sheet.... Quote Link to comment Share on other sites More sharing options...
Kranz Posted March 20, 2007 Share Posted March 20, 2007 No, only get it skimmed if it's not flat. Otherwise just make sure the surface is very clean (possibly get it lightly resurfaced but don't take any meat off it). Needs pressure testing though, definitely. If there is the possibility that the HG has been compromised but the cause cannot be found a cleanup is worth while. This will at least ensure the surface will not cause the gasket to fail in the future (if that was the problem in the first place). Quote Link to comment Share on other sites More sharing options...
cookci Posted March 20, 2007 Author Share Posted March 20, 2007 Problem with pressure testing heads is the cracks often do not not open up and start leaking until the head is up to working temp, and it's not possible to duplicate 900 degree exhaust gasses through the ports and 100 degree water temps whilst it's clamped to a rubber covered sheet.... lol ive got to laugh now. the bloke seemed to think he could see evidence that the HG had gone on no 6 cylinder. He knew this by looking at the pot???? Quote Link to comment Share on other sites More sharing options...
cookci Posted March 20, 2007 Author Share Posted March 20, 2007 ARe you 100% sure you were getting exhaust gas in the coolant? If not it could be micro-fractures in the plastic radiator end tanks. i was getting gas coming up through the radiator (could see the bubbles) had a test done on the gases and the test proved it was exhaust gases! We did the same test on 3 other cars and twice on mine. It only changed colour on mine. Of course it was using coolant also Quote Link to comment Share on other sites More sharing options...
cookci Posted March 20, 2007 Author Share Posted March 20, 2007 really wish id of taken it to you now chris for a new engine but as im not paying for the repairs i didnt have a 100% say in it walking sucks! Quote Link to comment Share on other sites More sharing options...
cookci Posted March 20, 2007 Author Share Posted March 20, 2007 although my car will probably come back 100% like new in a week :) im being optimistic as i get told off by the missus when im negative honestly though the bloke doing the work just doesnt want to put it all back together until he's 100% sure what the problem was which is only a good thing. I guess this might not be possible though? Quote Link to comment Share on other sites More sharing options...
Kranz Posted March 20, 2007 Share Posted March 20, 2007 Problem with pressure testing heads is the cracks often do not not open up and start leaking until the head is up to working temp, and it's not possible to duplicate 900 degree exhaust gasses through the ports and 100 degree water temps whilst it's clamped to a rubber covered sheet.... The hot pressure test rig I previously used at work had clamped ports, a head gasket to bolt down onto the jig and was nitrogen pressure fed to quite a few bar. And was done inside a explosion proof chamber. I'm guessing the garage hasn't got this?!! Quote Link to comment Share on other sites More sharing options...
Kranz Posted March 20, 2007 Share Posted March 20, 2007 i was getting gas coming up through the radiator (could see the bubbles) had a test done on the gases and the test proved it was exhaust gases! We did the same test on 3 other cars and twice on mine. It only changed colour on mine. Of course it was using coolant also I read that in your other thread.... so it must be a gasket/head/block problem. Its very unlikely to be the block, or a piston would have come out of the side by now! The head itself can crack around the exhaust valve seat, combustion chamber face or exhaust ports in that order of probability. The gasket can fail due to being over pressured (too much ignition advance causing knock), over temperature (coolant running out) or due to the head losing its clamping load (not fastened down enough or overheating causing it to warp & even lose its heat treatment and become soft). There's only so many places to look. Maybe if the pressure test doesn't show up a crack it could be dye penetrant tested. Quote Link to comment Share on other sites More sharing options...
cookci Posted March 20, 2007 Author Share Posted March 20, 2007 not sure what pressure test equipment he has TBH. whats a dye pentrant test? I think the timing was out a bit TBH and the the problem started soon after replacing the rad cap which was leaking and probably caused it to overheat Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted March 20, 2007 Share Posted March 20, 2007 I'd just buy a known good used head and save yourself a lot of grief. Quote Link to comment Share on other sites More sharing options...
cookci Posted March 20, 2007 Author Share Posted March 20, 2007 how would i know that was any good though? The only thing i can think of is buy one from someone on here? Quote Link to comment Share on other sites More sharing options...
cookci Posted March 20, 2007 Author Share Posted March 20, 2007 have you got one for sale? Quote Link to comment Share on other sites More sharing options...
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