1985 240 with ~200,000 miles.

We changed to semi-synthetic oil without changing filter immediately. Shortly after this the oil cap started to steam/smoke when openned hot and the dip stick had the brown gunk/milkshake build up of a blown head gasket. With a warm engine the exhaust was fairly moist looking.

Changed the oil 2x with normal oil and filter and now the oil is running amber with no gunk but still steaming slightly from the cap when hot.

Compression tests on all 4 cylinders running ~125 psi.

O ring on water pump also leaking coolant slightly (due for replacement of water pump but don't want to fix if related to a head gasket issue)

Could the steam/gunk just be from the extra detergents in the synthetic oil or do we have a head gasket or other problem? Any more diagnostic hints?

Thanks.

 

Have you checked the flametrap under the intake yet? If it's completely clogged up, condensation will build up in the crankcase.

If it's clean, then it could be a head gasket that is blown between a coolant and oil passageway. Lucky for you, a head gasket replacement doesn't look to be too bad on the SOHC engine.

 

Is the flame trap the 3 way joint just to the left of the oil dipstick in the photo?

I couldn't locate anything lower down that seemed correct to my unknowledgeable poking and the joint looks approximately like the ones I've seen in photos. It seems that there are relocation kits but I'm not sure where they relocate to.

If this is the flame trap, can I pull off the hoses and clean it or is it the older type that isn't cleanable? What can I clean it with?

 

Yeah, that thing. You can take it apart and clean it. If you have the old metal trap, you should get a plastic one because those are supposedly better. I'm pretty sure you can clean the old ones with some Carburetor Cleaner, not positive though.

 

Well, I doubt that the "semi synthetic" oil has anything to do with the possible HG issue. Semi synthetic is about 10% synthetic, and it should make no difference in a 230F motor. If the oil is clear now, and there are no other symptoms I wouldn't worry about it... But do service the trap AND the separator (the plastic box that the trap goes into).

 

Steam in the crankcase is not an indicator of a blown head gasket. It is an indication of moisture in teh crankcase, which is a normal occurence every time you run an engine or let it sit after being run.
As others have said look into the PCV system.
Head gasket failure should not be considered unless several of the warning signs are shown, and then it should be checked further before acting on it. Too many uninformed people spread "OMG! BHG!" around on internet forums, leading people to misdiagnose basic problems as head gasket.
So relax and look further.

 

indeed. head gasket failure usually results in one or more of the following...

1. coolant leaking from the head-block interface, usually below exhaust port 4
2. coolant in the oil (oil turns creamy)
3. exhaust venting out through the coolant tank

the first may be temporarily tolerable, as long as you keep an eye on it and keep topping off your coolant. the other two mean you need a head gasket, right now

 

the flame trap looked clean but the medium hose going down along the engine block (still need to trace exactly where it goes) had lots of creamy residue. I'm contemplating tracing it, removing it, and cleaning it but am interested in the box. My dad has had Volvo's for years and mentioned the flame trap but not the box when I spoke to him the other night.

Where is the plastic box (breather box?) mentioned in these posts? - do I just trace the gunky hose or is it the metal box higher up in the engine attached to the small hose?

Thanks a bunch.[IMG]file:///C:/Users/Fred/AppData/Local/Temp/moz-screenshot-3.png[/IMG]

 

per my parts catalog, the trap and plumbing looks like...



IIRC, host 9 goes to the air plumbing between the air filter and the AMM, and hose 8 goes to the intake manifold. not sure where that hose out the bottom goes off the top of my head, it may just dump out on the ground.