In my last installment, I was bemoaning my fate. I own a 1996 850 -base model- with 82000 miles and a leaking rear main seal. I posted a question inquiring about the cause of early seal failure and was told that excessive crankase pressure was a possible culprit caused by a plugged vacuum hose into the flame trap or a plugged oil trap.

After saving my pennies (many pennies) for a month or two, I had my trusted tech replace the rear mail seal to the tune of $450. He said the improved volvo main seal (more felt in the new seals at a cost of $27) was all that was necessary to "solve the problem". I said what about the vacuum line or the oil trap? He resisted and delayed as there was not a problem here. I persited and finally convinced him to replace the oil trap and the vacuum line from the vacuum tree to the flame trap. The result was the oil trap and attached hose were clear, however the vacuum line to the flame trap was plugged. This caused excessive crankase pressure and made my rear main seal leak.

Moral of the Story:
Always clean you flame trap when you change your oil and filter as I do every 3000 miles. Even if you do this you may notice oil leaking around your filler cap or your dipstick being blown out and/or your rear main seal leaks slightly, check your vacuum line from vacuum tree to the flame trap to see if it is plugged. If it is not plugged you may need to check the oil trap (under the manifold) for hose blockages or install a new oil trap. This costs more money or time in labor but is cheaper than an additional rear main seal.

Thanks for the pre-rear main seal replacement advice brickboard people. You may have saved me from doing the job again.

Can you tell me what is a flame trap..where is located?

OK, I'm a little confused. I was under the impression that the N/A cars had a flame trap only, and not an oil trap. I thought only the turbo cars had the oil trap. Someone please correct me on this if I'm wrong.

Wow, you only paid $450 to get the rear main replaced? That sounds like a pretty good deal, where are you located? I shopped around out of curiosity and the best price I got was $675. I'm getting ready to do this job myself on my 1993 850 in the next few weeks and it's quite involved. I'm pretty confident I can get it done in one day but I've set aside two just in case. The motor needs to be suspended from the inner fender rails so that the front subframe can be lowered and the transmission dropped out the bottom while the engine stays in place. However, in order to get that far the halfshafts have to come out, the sway bar and end links, and the steering rack, not to mention plenty of other odds and ends. It's gonna be fun, I'm going to document the job with digital pics if anyone else is interested in tackling this repair!

When I spoke to the indie machanic that quoted me the price above he said that alot of these rear seals just fail due to age and mileage. He wouldn't expect a rear seal in an early 850 to survive much past 100k even if the flame trap were spotless, which seems to be the case with my car. The seal started leaking slightly at around 101K (1/2 quart between changes), and my flame trap is clean enough to eat off of. Now, 6 months later, the leak has gotten a bit more rapid and it's to the point that I'm not comfortable with it. Time to get greasy...

The parts guys called it an oil trap. I have also heard it called an oil- vapor separator. It connects to a hose that runs from the flame trap down under the manifold (which has to be removed to get to it) and is attached to the lower part of the engine front by a number of hoses and clamps. It is about 8 inches long and 4 inches wide and resembles a half cylinder with the flat side connecting into the crankase. It is a hard plastic construction, costs about 30 dollars and has been modified on later 850 models. I have been told that if it or its hoses and clamps plug up due to poor oil change history, it can cause excessive crankase pressure which causes main seal leaks. Since I am not the first owner of this car, the previous owner could have been a jerk and not changed the oil regularly and contributed to a plugged trap. This was not the case however, the vacuum line from the vacuum tree to the flame trap was clogged and is now cleared. I would not expect to replace the oil trap in the future as I change the oil regularly.

I can respect anyone who can attempt a rear main seal change or evaporator replacement on their own. I am merely a driveway tinkerer and would not try the above mentioned procedures at home. Just knowing enough about such complex procedures to deal with a technian has saved me from being taken to the cleaners many a time.

I just did the job you are talking about. Had to change the clutch on my 93 850 and did the rear seal why I was in there.I replaced; clutch assembly, all three engine mounts (one was leaking and the right side mount was torn), sway bar links, ball joints, sway bar bushings, front axle nuts(you can't reuse them), top steady bar bushing. And don't forget the Volvo synthetic trans oil and the pop rivets for the left wheel housing cover. The replacement flywheel bolts were a pain, they are TORX so I tossed them, put lock-tite on the old ones and put them back in. The Haynes manual says you can't reuse the sub-frame bolts but I did. I used an engine hoist (cherry picker) to support the engine so I could lower it. Other misc items, remove the fan, it makes it easier to get at the starter, good luck trying to remove the ball joints I had to drift them out from the top after the axles were removed. I supported the steering rack from above with a 2x2 across the strut towers and wire down around the rack. Haynes states you disconnect the left side and back off the right side of the sub frame, I removed the whole thing and can't imagine doing it their way. Good luck.

Hey, thats all great info, thanks. Would you happen to have a part number for the axle nuts?

I plan on using a cherry picker to support the engine also (gotta remember who I let borrow it). I started putting together an assembly to span the inner fenders using a piece of 1.5 inch thick steel rebar but the whole idea seems kind of stupid, even using the Volvo supplied piece, and I can imagine they want a fortune for that thing as well. I think the engine hoist will be much safer and easier to work with. Where did you hook onto on the engine with the hoist? The manual says to suspend the engine from the upper torque mount attachment points but doing that seems to me like the engine will be able to roll toward the front of the car unless you really start to lift on it. I was looking for some factory lift lugs but there don't seem to be any on the top, I guess because they always intended for the motor to go out the bottom. Thats a good idea about suspending the steering rack, I was planning on just removing it but your way might save some time. I don't believe I will have to remove my ball joints though, just seperate them from the steering knuckles. They seem OK otherwise, so I ain't gonna mess with them. I was planning on doing the engine and subframe mounts though, even if they look OK they're usually soft.

Did you say the flywheel bolts were hex head and replacement ones were TORX? I thought the manual said the bolts already in there should be TORX, T-50 to be exact. I guess I'll see when I get it open. Lets see, what else, exhaust, starter, airbox and battery on the top, and all the various wiring and hoses for the tranny. Anything I miss? How hard was the seal itself to seat, I've heard it can be a bit tricky? Oh yeah, how long did the whole job take you?

Man, I think I got the entire engine and trans out of my Triumph TR-6 in under an hour, I miss the old days when cars were simple.

i could drop the engine out of my 914 in 20 minutes....sometimes I still miss that car(but not the sound!)