Car: 1991 Volvo 240


There was oil in the coolant expansion tank. I did a leak down test and could hear air bubbles in the radiator so assumed the head gasket was bad. I subsequently replaced the head gasket.

Current status:

I worry a LOT and am not confident in my work. I am not sure that I got the head gasket on correctly.

After replacing the head gasket I did a leak down test and did not hear bubbles in the radiator. I did, however, do a vacuum test at the intake and see a sharp drop in vacuum when I rev the engine. I believe the engine is running a little rich.

I don't notice any "sweet" smell associated with a leaking/blown head gasket. I tested the O2 sensor with a DMM and the voltage is 0.56 V.

I can test with an oscilloscope, but assume it is OK.

There is sometimes a very small amount of white smoke and water when the car is first started, but then goes away. I should emphasize that the amount of smoke is very small.

I think most people would not notice it, but I do because I am looking for it.

I have not noticed any oil in the coolant expansion tank, coolant in the oil, or coolant in the transmission fluid.

Next Steps:

Should I get a kit to test for combustion gasses in the expansion tank? Would this give me any additional information that a leak down test would not? Are there any other tests that I can do to make sure I installed the head gasket correctly?

EDIT: A video of the smoke/fluid from the tailpipe is available here.. A video of the vacuum at the intake is shown here.

1 Answer 1


There's several tests mentioned on this question How to test if head gaskets are blown?

I'd run a compression test and check how all cylinders are sealing and what variability you find across the block.

  • Thank you for the link. The information is useful, however, it does not address measuring vacuum at the intake. Is a combustion test at the expansion tank/radiator more sensitive than a leak down test? Jan 3, 2018 at 3:52
  • Note that my question now has links to videos of the vacuum at the intake and smoke at the exhaust. Jan 3, 2018 at 4:10

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