1999 S70 GLT Sudden coolant loss and power loss

[rmmagow]

The hydrocarbon test is the definitive test. Maybe a second test using the fluid stuff from AutoZone? But what he did makes sense and is a reasonable way to check for that.. I don't know how bad 138 actually is but I'd be inclined to think the HG is blown. Compression test might not pick up a slight HG leak.

[erikv11]

All of the key head gasket tests/indicators (HC test, compression test, oil in coolant, coolant in oil, sweet smelling steam out the tailpipe) are the same: If you get a positive result, then very likely the problem is the head gasket. I say "likely" because some require follow-up to be sure it is not something else. But if you get a negative result, then don't start celebrating just yet because you need to check by the other methods too. The reason for this is because the head gasket can blow in several different ways.

So if the HC test says there are HC's, that is pretty definitive. I also have no idea what 138 means but if that is a high number, and given your description of events in the first post, then it is looking like a blown HG. rmmagow's suggestion to test it yourself is a good one if you just want to see the test results in a form others on here can validate for you.

A compression test could back up the HC test, but if it didn't that wouldn't necessarily be good news.