Tell me about it. When they're on the dyno, the tailpipes are pointed right at our loading dock. Some very healthy sounding stuff indeed.
Murphy's Law
- Thread starter JD1964
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Tell me about it. When they're on the dyno, the tailpipes are pointed right at our loading dock. Some very healthy sounding stuff indeed.
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Completed the test for combustion products in the coolant. It passed. The instructions say to bubble through the fluid for 2 minutes. Well, I did it for 4 minutes and the test fluid remained blue indicating no combustion products in coolant. Is it possible to pass this test and still have a problem with head gasket leak only under boost?
Next is compression test.
Next is compression test.
Last edited:
mikestang63
SN Certified Technician
you need to make certain the engine is up to operating temperature and there is enough of an air space on top of the radiator. It is certainly possible that the HG is bad but the test is not showing exhaust gast in the coolant. Have you done a compression or leak down test? That will tell you for sure.Completed the test for combustion products in the coolant. It passed. The instructions say to bubble through the fluid for 2 minutes. Well, I did it for 4 minutes and the test fluid remained blue indicating no combustion products in coolant. Is it possible to pass this test and still have a problem with head gasket leak only under boost?
Next is compression test.
I was planning on a cranking compression test but it appears my gauge lost its check valve. Guess I have to get another one. I've always done cranking compression tests in the past. I've never done a leak down test. I have a compressor capable of 100 psi or so. Is that enough to do an adequate leak down test? I cant imaging the tools or fittings being too expensive. Can you advise? Thanks.
Thermostat checks out good. Put it in a pot of water on the burner and monitored with thermometer. It's a 180 thermostat. It began to open at 180 and was fully open by 190. Nothing wrong there.
Test the test fluid. I was doing the test and it wasn't changing colors. I put some in a medicine cup, and held it by the exhaust pipe it stayed blue. The fluid has a shelf life of two years. I guess my test kit I bought had been sitting on the self awhile. With new working fluid it turned yellow on me pretty quick, Ill be pulling the heads this weekend. Ughhh
I've been attempting diagnostics before tearing this thing down. The fact that I goofed and reused TTY headbolts last time is reason enough to tear it down even if my preliminary diagnostics cant find a specific problem. I'm waiting for a check valve for my compression tester and I also have a leak down kit as well. Since all the plugs are out and everything is ready for cranking compression test, I'll just wait for the check valve and do that test before doing the leak down test.
Having said all that, maybe someone can confirm something for me. I may find no evidence of failed head gasket via whatever tests I run. It might be because the cylinder pressures I'm using under these test conditions are not high enough to recreate the problem. Meaning that, while engine running at high rpm under substantial intake boost, cylinder pressure gets high enough to release combustion into the water water jacket. Does this make sense?
What would the actual PSI be in the combustion chamber of a boosted engine running at high rpm?
Having said all that, maybe someone can confirm something for me. I may find no evidence of failed head gasket via whatever tests I run. It might be because the cylinder pressures I'm using under these test conditions are not high enough to recreate the problem. Meaning that, while engine running at high rpm under substantial intake boost, cylinder pressure gets high enough to release combustion into the water water jacket. Does this make sense?
What would the actual PSI be in the combustion chamber of a boosted engine running at high rpm?
I wouldn't know what the cylinder pressures would be but if your car is pushing coolant out of the overflow, that joker is blown! Nothing should be forcing it out under boost. This was my issue. I couldn't really detect a problem just putting around and I did not go through the motions of compression testing and radiator testing but I know that coolant should not be under that much pressure hence why I pulled my heads. Albeit I smoked mine from a broken serpentine belt and running the car too hot, I still had evidence of a blown hg in 2,3 and 7,8. Its a lot of work but it has to be done......Git ta woek!!!
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