'96 850R - smoke at startup, PCV test and turbo questions

rhalkyard · Post by **rhalkyard** » 21 Mar 2015, 21:19

I have just noticed that when I start my 850R from cold, there is a sizeable cloud of blue smoke from the exhaust as I pull away -- big enough to spot in the rear view mirror. My initial thought was valve stem seals, but I've never noticed any smoke after idling in traffic or when coasting on a closed throttle. It only seems to happen when pulling away after starting from dead cold. It's hard to gauge when this started happening -- it's only just got warm enough for the clouds of condensation to stop forming -- but I'm pretty sure that it wasn't doing that last fall, although it was running thicker oil then (I changed to 5W-30 from 10W-30 in the middle of winter after it was struggling to build oil pressure on startup on subzero days, but I ended up doing the pickup tube seals anyway).

I have read posts about blocked PCV systems and dying turbochargers causing smoke on startup, too, but since I'm not really in a position to tackle all of the possible causes, I thought I'd put this out there for the collective wisdom of the internet to weigh in on before I dive in. If it's valve stem seals, I suppose that the best thing to do is just live with it until I pull the head for some other reason, but if it's something that I can fix relatively easily, it would be nice to not leave the neighbours in a cloud of smoke every morning.

As far as the PCV goes, there's no observable smoke from the dipstick tube at idle, but there doesn't feel to be much of a vacuum either, and revving the engine yields a small puff of smoke from the tube. Is this considered within acceptable limits for a 214,000 mile engine? Service records from the previous owner say that the PCV system was serviced 25,000 miles and 5 years ago, and 'inspected' (whatever that means) 10,000 miles ago and found to be okay. As it is, the engine has a bunch of oil leaks, but reading between the lines in the car's extensive service history, I suspect that might be from pre-existing seal damage -- the service write-ups consistently mentioned evidence of leaks for about a year before the PCV was last done, and kept mentioning them afterward.

The intake hoses are all pretty oily, but there doesn't seem to be huge quantities of oil pooling anywhere, and the intercooler weep hole never shows any signs of dripping. I did find a page on a Saab site detailing a so-called "blue smoke syndrome" caused by leaking seals on the exhaust side of the turbo -- http://www.saabnet.com/tsn/members/gall ... w&id=12972 -- is this a known phenomenon on the 850 as well? There's no evidence of any turbo work having been done in the car's life, so I can only assume that it's 214,000 miles old, too. It doesn't make any noise, and seems to boost well, but at that mileage, should I be rebuilding it anyway?

Post by **Ozark Lee** » 21 Mar 2015, 23:12

Smoke on startup is usually bad valve stem seals. The turbo won't really smoke until the car gets hot when its hot side oil seal fails. If the cold side seal was real bad then the intercooler lines would be dripping oil rather than the typical film of oil.

...Lee

Post by **shaker_chi** » 22 Mar 2015, 14:43

Take a look at your tail pipe. Do you see any oil on the tip of it? If you do, it's probably the valve seals.

Good luck.

Post by **polskamafia mjl** » 22 Mar 2015, 17:51

shaker_chi wrote:Take a look at your tail pipe. Do you see any oil on the tip of it? If you do, it's probably the valve seals.

Good luck.

Can the oil really make it all the way through the turbo and length of the exhaust without getting stopped along the way? I would expect it to burn in the turbo and downpipe or to get stopped inside the cat.

rhalkyard · Post by **rhalkyard** » 22 Mar 2015, 20:17

Thanks. There's no doubt that there's oil being burned somewhere, but it's just a question of where it's coming from. I had a friend follow me today and they did see a small amount of smoke at high vacuum and after pulling away from a stop, just not enough that I could see it in the mirror. Sounds like it might be valve stem seals, then.

I might try switching to a thicker oil now that the weather has warmed up a bit, and see if that staves off the inevitable for a while longer. The valve stem seals look to be a bit of a daunting job, but thus far, my ownership of this R has been all about pushing me outside of my auto-repair comfort zone, and I don't see that as a bad thing.

I'm still wondering about the results of that PCV test, though. Everything that I've seen just talks about the absence of smoke at idle. Would a puff of smoke on revving the engine and a lack of suction at idle indicate the beginnings of a blockage, or is that normal on a higher-mileage (214,000 mile) turbo engine even with the PCV system in good shape? I don't really want to go and tear into it if it isn't necessary, but if it's just on the edge of failure, I'd rather tackle it now rather than wait for it to get worse.

MrGruffles · Post by **MrGruffles** » 24 Mar 2015, 11:39

I agree with the others: blue smoke upon cold start after sitting sounds like valve seals (oil leaks through into the cylinders as the car sits, then burns off when you start it.)

A good PCV system check is to remove the oil filler cap and rubber-band a latex glove over the opening: At idle the glove should suck in. If it inflates, it indicates a clogged PCV system and/or PTC nipple or possibly clogged or disconnected hoses.

For what it's worth, my 1994 850 Turbo billowed out clouds of greyish-white smoke when the turbo oil seals went. (It is my understanding that oil burned in the combustion chamber produces blue smoke whereas oil vaporized later on in the exhaust produces the grey/white.)

Post by **rspi** » 25 Mar 2015, 06:35

What climate are you in? Are you using synthetic oil? I have read of these 15g turbos lasting well into the 300,000 mile range with no problems.