This is a non Turbo 850 GLT with 416 K on her.
I was just going onto the highway the other day and as I accelerated the car started to shunt/jerk.
Thought it might be some post winter moisture in fuel or lines and added some stabilizer and
after a couple minutes it ran fine. Next day noticed oil pool when leaving parking space and smelled
burning oil after a bit. Investigation showed oil leaking in engine particularly down right side in distributor area. Had to change oil anyway so put car up and degreased oily areas, changed oil & filter, removed the plate behind oil cap (cylinder plate?) as there was evidence of some oil leakage around bottom of oil refill opening. There was some oil pooling in depressions under the plate. Checked around PCV valve and found a small hole in hose to PCV valve and replaced hose.
Started engine up and after a minute or 2 got oil seepage again... appeared to be coming out of seal behind distributor.(got little puffs of oil smoke seeping from this area. Difficult to tell exactly. My question is: is this the front or rear camshaft seal ? (I cannot find a part listed as distributor shaft seal) I am also going to replace the PCV valve and the oil filter cap gasket. I have not replaced the Distributor cap and rotor in a very long time and figure that I will do that also. Is The flame trap something I should consider replacing and is it hard to find / get at? Where exactly.

I have been reading a lot of posts and don't think that I have a main seal issue as the leak appears to be much higher on the motor.
So I need to know which camshaft seal it is (front/rear) and if I should replace / check the flame trap wherever it is,,, also any other suggestions while I'm at it?
Thanks

tmannian wrote a solid response.

Probable the EGR system is plugged building up crankcase pressure and forcing oil
by the seals . I just got may 850 last summer with abt 200k on it and found the egr was completely
plugged especially at he port where the egr conrol valve mounst on the intake manifold.
I found that taking the intake manifold off was a pain where you sit down, and wonder if you could
just remove the egr valve and throttle body and clean out the blockage without pulling the
intake manifold. In any case you can't have the EGR system plugged up or you might have the rear
main seal blown out which is a major repair.

I was told by a local Volvo guru that ordinary oil really messes up the 850 engine and that it's way
better to run synthetic. So I switched, then to find out that the engine leaks more for a while as the
dyno oil deposits and the engine seal surfaces change some how. I tried BARS rear main seal
treatment and it seemed to work after more than 600 miles and not the 250 miles they say.

There's some good writeups on the EGR repairs.

I wonder if there's some EGR mods out there that could improve on the Volvo design and
prevent the crankcase pressure building up too much. maybe there's some way to let excess pressure vent
?

Good luck, and now the weather is getting better for us driveway mechanics.


Bill

Rear cam seal is by the distributor on the head. Front cam seal is over by the timing belt. The main seal is between the engine and the transmission. Replacing the rear cam seal is pretty straightforward. Remove everything in the vacinity, pull out, put new one in, and put it back together. If you've never taken off the air box, its actually quite easy. Pull off all the connections to it, then pull it up and toward the engine.. It comes right off. Took me a good hour to learn that the first time I had to do it..

The oil filler gasket can leak, but I assume it was the PCV hose that you noticed had a hole in it. That'll drip down all over your plugs (I've noticed #3 gets it the worst) and give you that jerking you noticed.

Flame trap is the little plastic housing that comes off the large plastic hose from your airbox to the intake manifold. If you have it, throw it away. It clogs up, which clogs your PCV system and they you've got yourself a lot of work to do. If I were a betting man, I would say the PCV system is clogged, and it has actually blown out the camshaft seal. That isn't a huge deal, replacing it isn't a great amount of fun but its OK. However, I would say clean out your PCV system ASAP.

This is a great write up on how to repair the PCV system Its for a turbo, so you don't have a PTC nipple, but a flame trap. Anyway, the author talks about removing the radiator fan to give yourself a little more room. I say do it. Doing so will "add" twenty minutes or so to the job, but having more access will cut your time right back down. Also, not cutting yourself several times on the fan is nice. And you can use a hose and clean some of the junk out of your radiator fins.

--
If you're not driving it "like its stolen," are you really driving?

Thanks guys... I am replacing the seal / flame trap etc. Am hoping that age (416K) has just caught up with the seal. Thanks for the reference on PCV system clean/ repair... really well done... may be the next step.