I recently noticed my '92 745 Turbo was losing oil. I refilled and it happened again (slowly by the way). After searching online I read that every 12k miles you are supposed to clean the oil trap which I didn't know about (I haven't driven 12k miles yet with the car but I think the old owner did terrible maintenance). Anyway, I filled up with more oil and when I went for a drive it was smoking under the hood but that was probably just from residual oil burning off of the exhaust manifold because I haven't seen that since. What I have seen though is smoke coming from the catalytic converter and clear signs of oil on the bottom of the cat and around the connector in front of it.
I have to drive 2 hours back home this week and I hope I make it, and then I'm going to clean the oil trap, but is there anything else I should do besides that? And do you think the cat is probably shot? I'm glad the 740 cat isn't too expensive but I would rather not replace it if I don't have to.
Thanks,
Jor

 

The oil trap shouldn't be involved in this.
How do you see oil in the bottom of the cat?
You could be burning oil and some the unburnt oil passing past the rings and working itself through the exhaust and the cat... Is there smoke coming out of the exhaust pipe? Is there oily residue there? If so, you may need more than a cat.

 

I can't get a super good look under the car, but the bottom of the cat looked black and smoking so I just assumed it was burning. I'm going to have to take a better look at it in the coming days. I haven't seen any smoke coming from the exhaust. I believe that if I pull the spark plugs I can see if oil is passing through one of the cylinders?

 

I'd guess you have an oil leak and that oil is ending up on the exhaust. The cat is the hottest part and the first place it would smoke from. All oil leaks will end up toward the rear of the car (air flow) - So front seals, valve cover, oil filter adapter/oil filter, rear seal and any transmission or power steering leaks are all suspects as this point.

Certainly a clogged PCV system can makes oil leaks and usage worse - so that system should be working properly.

 

I'd guess you have an oil leak and that oil is ending up in the exhaust. The cat is the hottest part and the first place it would smoke from. All oil leaks will end up toward the rear of the car (air flow) - So front seals, valve cover, oil filter adapter/oil filter, rear seal and any transmission or power steering leaks are all suspects as this point.

Certainly a clogged PCV system can makes oil leaks and usage worse - so that system should be working properly.

I will definitely check those things. Do you think I might be able to rule out the transmission and power steering leaks though since I am losing engine oil? Or maybe they would be good to check anyway.

 

A 30 year old Volvo can leak from anywhere -

 

If he is leaking a lot of oil I would look at the turbo. I have an oil leak from the head between 3 and 4 and it's been leaking for over 200k miles. I lose a quart over 2 to 3,000 miles. Not a big deal and usually get the undercarriage washed at the carwash every 2 weeks.

 

You probably have oil on the tailgate and rear window too...
I know your pain; I tried the front seals (timing belt change); I tried oil separator cleaning and replacement; I replaced the valve cover gasket; I replaced the oil cooler hoses (oil filter); no real success.
I eventually pulled the engine and did a full seals refresh. The oil cooler standoff needs new oil rings and the rear main seal needs replacing, that's your culprit. I also replaced the transmission pan seal and the input shaft seal.
The turbo oil drain line needs the gasket at the turbo and the oil seal at the block.
That has solved my engine oil leaks, now all I have to do is take care of the power steering hemhorrage.
While the engine is out you can take care of a number of other maintenance items, too.

 

No. Transmission bell housing orings leak. You have a 30 year old Volvo. I was resealing transmissions and fixing trans cooler lines when they were 15 years old. - So anything is possible.

 

yeah it might be time to do a complete do-over with everything you said. I was praying that I wouldn't have to but I guess I may have to bite the bullet
thanks everyone for the advice

 

I had a messy oil leak last summer. After some searching, I suspected it originated from the two orings on the oil filter standoff. I replaced both, and the oil leak disappeared. You can replace those without removing the engine. Mine is a 93.