850 10v smoke on idle

[lightyears]

Hi guys.

My 850 has all of a sudden started smoking very blue
Smoke when on idle or blipping the throttle, both cold and hot makes no difference at all, it also makes a horrendous burning smell at this time. The car has had regular oil changes at 5K, is relatively low mileage at 120k. The PCV was changed just before I bought it but I had noted a little puffing from the dipstick. Any thoughts much appreciated

[Rich850R]

Originally Posted by lightyears

Hi guys.

My 850 has all of a sudden started smoking very blue
Smoke when on idle or blipping the throttle, both cold and hot makes no difference at all, it also makes a horrendous burning smell at this time. The car has had regular oil changes at 5K, is relatively low mileage at 120k. The PCV was changed just before I bought it but I had noted a little puffing from the dipstick. Any thoughts much appreciated

Do you have proof the PCV was done, even if so the aftermarket parts are crap in comparison to Volvo

Do a glove test initially for the PCV


Hope it’s not the rear main oil seal

[lightyears]

The PCV change was documented on hear by the previous keeper😁. On further investigation there appears to be a significant drip of oil at or around the slot on the bottom of the gear box, wasn’t there a week ago. I’m thinking that they may be related to the rear seal?

[Rich850R]

Originally Posted by lightyears

The PCV change was documented on hear by the previous keeper😁. On further investigation there appears to be a significant drip of oil at or around the slot on the bottom of the gear box, wasn’t there a week ago. I’m thinking that they may be related to the rear seal?

I’d suspect rear main….ouch

[Luxobarge]

Originally Posted by Rich850R

I’d suspect rear main….ouch

Indeed, but be very sure it is before you go pulling it apart. I had this, and figured it could also be the turbo oil pipe (assuming you have one) but it turned out to be simply the camshaft oil seal had popped out - probably also caused by blocked PCV, which I'd already fixed.

In any event it sounds as if you need to re-investigate the PCV, especially if it fails the glove test. Remember the port into the crank case can get blocked with carbon sludge, so even if you replace the PCV components if this is blocked then it still won't breathe properly. You might be able to clear it from above, but the best and most thorough way is to drop the sump. Quite involved to do this, but nothing like as bad as rear main seal!

[Baffler]

Originally Posted by Luxobarge

In any event it sounds as if you need to re-investigate the PCV, especially if it fails the glove test. Remember the port into the crank case can get blocked with carbon sludge, so even if you replace the PCV components if this is blocked then it still won't breathe properly. You might be able to clear it from above, but the best and most thorough way is to drop the sump. Quite involved to do this, but nothing like as bad as rear main seal!

Picture of said oil return port in this thread: PCV system theory & diagram anyone?? (courtesy of MikeAlder)

[4x4]

The oil at the gearbox bell housing will be the rear main seal, however that would not cause the smoke at idle. I would expect valve stem seals to be the cause of the smoke

[phatboy130]

I had a 1994 850 10 valve a few years back, well looked after, similar mileage which started doing this, unfortunately in my case, the rings had gone on no.5 cylinder, really hope this isn't your problem, but might be worth a quick compression test if you can get one done? I believe some of the early 850's had this problem with the rings / bores...

In my case, I scrapped it sadly....

[lightyears]

Thanks for all your suggestions so far, I will work through some of the suggestions and see what’s what. I’ve got a bad feeling though, the smoking has come out of the blue after an extended rest period of about 2 weeks.

[Baffler]

Sudden onset of smoke would kind of rule out valve stem seals as they are usually gradual. If it were mine I would first identify as to which seal has actually popped, rear camshaft or crank, and then get the sump off for a proper look to see what's going on below and inside.