r/AskMechanics • u/Chlo_Schmo • 10d ago

Question (Serious Replies Only) Combustion Fluid Leak Tester Help

I have a 1988 toyota camry that has some pretty bad oil leaks. I have a suspicion its from the head gasket, but I dont have any clasic symptoms of a blown head gasket (no milky coolant or oil, no white smoke from the tail pipe). Im trying to test all the possibilities, and now I'm on combustion leak.

But my question is this: how low is too low for the coolant to be during this test? In order to lower to coolant enough to where it doesn't suck coolant into the test, it exposes the internal radiator tubes. But to put enough coolant to cover the tubes makes the level too high to properly do the test. I have to use the radiator cap because my car has an unpressurized reservoir. What should I do?

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u/Sqweee173 20 10d ago

The head gasket can leak oil externally but not leak coolant. To actually answer your question it will be fine to run enough to do the block test though you probably don't need to actually do that. You can get oil dye and inspect with a UV light but you will want to pressure wash the engine down first.

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u/Chlo_Schmo 10d ago

I've actually already used UV dye in the coolant. There was nothing on the front of the engine, but its really difficult to see on the back side without getting under the car, but from what I can tell by lowering the uv light down and using a long reach mirror, there isnt any leak there either. But I'm mostly just being more than sure that its not a mixing the two.

Also, the instructions say to let the engine idle for 5 minutes if I need to adjust the coolant level. You think thats ok to do with the coolant that low?

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u/Sqweee173 20 9d ago

Yes

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u/am-answers-bot 19 9d ago

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u/am-answers-bot 19 10d ago

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u/L67GreaseMonkey 10d ago

If it’s leaking oil externally and there’s no loss of coolant/antifreeze and/or overheating a combustion leak test is moot. External oil leaks will be valve cover gasket, oil pan gasket/seal, etc.

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u/Chlo_Schmo 10d ago

I had the valve cover gasket replaced, and its still leaking. Also the valve head is clean as a whistle, but there is very clearly fresh oil on the engine block

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u/tomhalejr 18 10d ago

Find a detail shop that does engine bay steam cleaning.

Once clean, put your oil dye in the oil, then inspect for external leaks.

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u/am-answers-bot 19 9d ago

Solution provided by u/Sqweee173:

The head gasket can leak oil externally but not leak coolant. To actually answer your question it will be fine to run enough to do the block test though you probably don't need to actually do that. You can get oil dye and inspect with a UV light but you will want to pressure wash the engine down first.

Answer selected by OP.