zekgb

The previous owner told me that my new to me 85 with 64k miles would emit a puff of smoke at startup after sitting for several days. We did a leakdown as part of the PPI and got 175-180 across all cylinders. Since returning to California with the car it has emitted exhibited a smokey startup pretty much every morning and has been using oil at a rate equal to a quart/1k. The car starts without smoking when warm/hot and passed smog with abusrdly low numbers just last week.

When replacing my heater valve last night i noticed a nice puddle of oil under the MAF. From the archives it appears that absent a compression problem that a leaky oil breather is the most likely cause of this type of behavior. Am I likely to find/fix this problem without a complete intake disassembly? Are there any writeups (preferably with pictures) that deal with an intake r/r on an 85/86? Any other potential causes that I should be looking at?

Thanks in advance,

Kevin

85 928s 64k Moss Green Metallic AT RMB

davek9

Hi Kevin, yes this is common, most will suck oil thought the crank vent baffle plate (where the oil fill is) an into the manifold. Look around that area there is a seal too which can dump oil into the valley, also PVC connection to the Pass side (US) cam cover.
Lots of threads on this, please do a search.

JHowell37

1 quart every 1k miles is within the normal range of consumption. It is possible to find the source of the leak without completely disassembling the intake but on a car that's 20 years old, you're just going to move the issue to the next weakest link in the chain. The intake r/r on the '85/'86 looks daunting but really isn't too bad of a job. The only diagram I used was the one that showed the vacuum line routing.

nosnow

Sounds like the oil filler/breather seal is leaking. Sometimes you can get a little more life by re-torqueing the bolts but the seal will probably need to be replaced. On my '82 you have to remove the intake and the water crossover. I think it is simular for your year model. Do a search for oil plenum, oil seperator, oil filler... there are tons of threads on this and there are a lot of little things that you mise well do while it is apart.

sharkmeister85

Seems there's been a few of us doing that job over the winter this year. Its not particularly difficult, but does open up a can of worms. There's lotsa gaskets, seals and hoses to replace. Got it all apart? Might as well replace the old (dangerous) fuel lines. How about powdercoat the peeling intake and cam covers? Have the injectors cleaned/refurbed? Replace old sensors? I did all that and more. Time, money and patience. But once every 20+ years isn't so bad.
Glenn

Imo000

I don’t believe this situation is related to the oil accumulation in the intake side tanks. Sounds more like when the engine sits over night or longer, the valve guide seals are leaking oil into the combustion chamber. Either the guides, the seals or both are worn.

Jim bailey - 928 International

I vote with Imo on this one oil in the V of the engine is NOT going to get sucked up into the intake for
a puff of smoke on start up . It maybe that the engine has a bit of blowby and vapors are pooling inside the intake especially during spirited driving that is fairly normal but that typically does not show on start up.

hacker-pschorr

Valve guides & seals would be my best bet.

the flyin' scotsman

Oil puff on start up is classic valve guide seal and/or the valves and guides. Residual oil in the cylinder heads leaks past the valve guide seals down the valve stem and into the combusion chamber is the valve is open or pools on top of the valve until you crank it over.

You can fix the seal issue without removing the heads.........ask me how!

davek9

Your right, bad valve seals won't show on a compression test. I was distracted by the oil in the valley and got off the original question.

Also I think a quart per 1k mi is kinda high... yes?

Jim bailey - 928 International

That amount of oil consumption is high for anything but a GTS... or track use

zekgb

I am feeling a bit nauseous about now.

Shane

What kind of oil are you using?

Not the end of the world, but it is an engine removal job to pull the heads, since the '85-'86 use studs instead of bolts.

zekgb

Previous owner had just completed a change with Castrol GTX 10w40 prior to my purchase (about 4k miles ago.)

hacker-pschorr

Valve guides & seals are a wear item - don't feel bad. My mechanic has seen 944 / 928's with worn valve guides in as little as 50,000 miles.

This might make you feel better. The Ferrari 355 my father is looking at has an issue wearing out valve guides prematurely. A valve guide job on these start at $7,000. So be happy you don't have a 355 Ferrari