I just bought a used volvo 740 turbo wagon for my son for $900. The body is great but it has a bad head gasket. I plan to pull the head and replace the gasket as soon as it gets warm enough here to work on the car. It is right around zero today and I just can't stay out there long enough to do any kind of work. My question is will I damage the car further by driving it with a bad head gasket. The only symptom is that the cooling system seems to get pressurized with exhaust fumes. The coolant looks good and so does the oil. There is no tell tale white exhaust smoke or anything like that. I know this is not a mercedes question, but the only message board I could find for volvo (brickboard.com) doesn't seem to be of the same caliber as this board. Thanks for all your advice.

You should read my reply to the MB head gasket question that is current. You should not drive the car and you should not let it set for the reasons I stated. A leakage of coolant into the cylinder is the worse form of failure and if there is hope that the problem can be solved with just a gasket it can not be left alone.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

SB - does it start looking like this by any chance?

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Jim

Yes Jim, and worse. Its hard to tell from the picture but the amount of verticle scoring in that case could have screwed the pooch anyway. If it requires boring and new pistons letting it sit isn'y as important. The real problem can't be seen in a picture such as this or in person as the real problem is the rings rusting into the piston grooves, which will cause the galled results that look to have taken place there for a different reason.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

The guy who sold me the car said a mechanic for another buyer (who didn't buy it) said the head gasket was bad because there were 600 ppm hydrocarbons in the coolant expansion tank. Should I do a compression test to confirm this before I start pulling the head? If the compression test shows uniform compression across all cylinders does this mean the gasket is ok?

If you've got hydrocarbons in the coolant you've got a bad head gasket, or even a cracked head. Last car I had that showed hydrocarbons in the coolant had cracks radiating from every valve seat. If it is the head gasket, it might not be blown yet, but heading that way.

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

Compression testing is not a good way to find a head gasket leak. Checking the compression only tests one way of leaking (the sealing of compression) and will only find one once the problem is major.

The methods of testing for exhaust gas in the cooling system is a good approach. Most head gaskets we do are failed with external leaks or are leaking coolant into the cylinder. We test for the latter by pulling the plugs and placing a cooling system pressure tester on the system. We pump the system to the cap pressure rating and leave it over night. The next moring we crank the motor being sure nothing is in the line of fire from the spark plug holes. Any amount of water/coolant coming from a hole is too much.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician