My mom has a 1994 940, non-turbo B230F with about 300,000 on it & it keeps blowing almost all of the oil out of the oil cap. I changed the flametrap & flushed the oil separator box in August of last year. What else could be causing this? We are afraid the motor might blow due to loss of oil, so we'd like to get this fixed asap.

-Calhoun

 

dumb question - is the oil cap gasket in good shape?

 

Sounds like it's time for a PCV system replacement. Pressure is building up because of a blockage in the system. See if oil is coming out of the dip stick tube also. Dead give away for a PCV system blockage. Best to fix this before a seal blows out somewhere.

 

Was the flame trap screen plugged? My guess is the PVC box under the manifold is plugged up and needs to be replaced. You also might have blown the front and rear crankshaft seal as well as the rear cam/distributor seal.

 

The flametrap was replaced in August of last year. At the time of replacement I also flushed the PCV or oil separator box as well. Surely it couldn't have gotten clogged up again so soon??

 

Flushing the large oil separator box may not have fixed the problem. You should replace the complete PCV system. It is pretty cheap. But before you do it get a pressure test done at the oil fill cap. If the pressure is so great that it blows by the gasket on the cap and you replace the gasket you will end up blowing the crank and cam seals. Also are you seeing the dip stick get blown up in the tube maybe 1/4 to 1" above the tube.

 

I ended up replacing the entire system: oil separator box, flame trap, & all vacuum lines/tubes going to the pcv system. The car is still leaking oil out of the oil cap(oil cap & seal are new as well). I believe it used to push the dipstick up but I don't think it's doing that anymore. Any tips as to why its still spewing oil out from under the cap??

 

excess crankcase pressure is a sign of blow-by, indicating your piston rings are worn. turbos are more likely to do this than non-turbos. a compression leakdown test will give some indication of how far its gone.

due to the cost of engine rebuilding, the relatively low cash value of these cars, and the common availability of junkyard motors, its probably not worth rebuilding, instead, finding a low mileage motor and swapping, if your car is otherwise very cherry, otherwise, find another 940.

 

If he had that much blow-by wouldn't his spark plugs be fouled with oil? And the tailpipe?

 

its blowing the other way, combustion byproducts into crankcase.

 

I understand the principal of blow-by but I've seen engines with worn rings that fouled their plugs.

 

I thought spark plug fouling was more likely from worn valve guides than rings?

 

The ones I've seen probably had both.

 

With heavy blow-by it isn't uncommon for the oil to end up in the air intake through the crankcase breathing system which of course can end up fouling the plugs. I have seen severe cases of this that driving the car looks like it is sending up smoke screens.

 

Exactly. For smoke to be blowing out the tailpipe it has to go through the combustion chamber first, and the plugs would be get their fair share.

 

it doesn't take much oil to make a BIG blue cloud...

we had an 04 camry with worn valve guides, it blew a big cloud of smoke each time it was started from cold, but once it warmed up, it didn't smoke noticably at all, and it didn't consume hardly any oil between changes. its plugs looked fine and lasted a long long time.