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[CrazyMe]

I just recently rebuilt the motor in my 82 931 (rebuilt head, new cam, new crank, the whole 9 yards). The turbo was rebuilt only months before the engline. I've already drove the car alteast 3k miles, making sure to follow the haynes manual to the dot on breakin etc. Now here is what the car is doing. When I let off of the gas (like whne coasting down a hill or coming to a stop) it smokes very very badly. Doesnt seem to smoke at all while cruising at a steady speed, and rarely smokes while taking off. Any suggestions on why or what to do?

[TroyDest]

Hey Crazy. What color is the smoke? That will help narrow it down. Blue smoke is oil, black smoke is gas, white smoke is water. Does the smoking seem to start about the same time as the turbo bypass valve opening? You should be able to hear it click when it opens and closes. If it starts on deceleration like you said, it only smokes when you're pulling a vacuum downstream of the throttle body. If the smoke is black, I'd suspect a leaking injector (cold start maybe). If blue smoke, oil is being sucked in when you pull a vacuum. I'd suspect leaking valve seals, rings not broken in yet..... Keep an eye on the smoke and determine whether it's oil or fuel. Have someone follow you while it's happening. Good luck, Troy.

[Zuffen]

I would make sure the decel valve was hooked up correctly and there were no splits in the elbows and hoses.

Also the decel valve itself may be bad. But if it worked fine before the rebuild I would say something is routed wrong.

But of course I'm waiting to here about the smoke color too.

_________________
Bob Dodd - 924turbo@cox.net
931 1982, 944 1982 euro, 924S 1988SE, 93 968 tip 06 Silver Cayenne S, 06 Black Cayenne S

I have Way too many cars, parts for the 931,944 and 951

[wdb]

there is also a rare problem that I've seen happen to a ford van when the rear seal in the brake master cylinder goes bad and brake fluid gets sucked into the intake system and burns ,you'll get white smoke out the tail pipe, If that happens change your oil immediatly ,because the brake fluid will break down the oil and cause your bearings to fail.

[larso]

valve seals

[larso]

Also the best way to smell for oil is to smell for oil. The color of oil is very confusing. Oil smells like rotten peanuts, overcooked peanuts....Oil can be white, purple, or black, so don't try and look at it and determine if it's oil or coolant, or water. I've tried, and after a year, I've tuned my nose. Given up on the "color". *ONLY* your nose knows.

That's right, ONLY.

WHen coolant burns, it smells sweet. This is not the case though, when your engine is blowing coolant with gas fumes. Don't think that if it isn't sweet, it isn't coolant. Coolant does not smell sweet when being burned with gas fumes. I've blown a head gasket in a 931 a long time ago, and the coolant didn't smell sweet. It only smells sweet when burned by itself (so when you first start the car up, for a split second it may smell sweet...but after a split second that it will not smell sweet).

Just some nosey points. Or maybe just my pointy nose.

Lars

[ This Message was edited by: larso on 2002-07-24 00:33 ]

[CrazyMe]

Hi, thanks for the reply's. It's definately oil (usually a bright blue smoke, though sometimes its a much lighter greyish color, and you can really smell it).

[Rick MacLaren]

I blew my engine last year. Cost me a bundle to fix. Still paying for it.

My advice?

1. Stop driving it now.
2. Find out the cause of the problem.
3. Pay for someone very very qualified finding the cause. Or, if you feel qualified, do it yourself and save some money. But DO IT properly.
4. Do not write off this oil smell as something minor until you have information specifying that it is indeeed only minor.

I give you quite overly conservative advice - I admit that fact. But the risk if it is NOT a minor glitch is, at best, extreme ($$$).

In recent months, I had ONLY a leaking oil filter gasket, but, cautiously, I had a shop go over the entire car to confirm that suspicion. Once they gave their stamp of approval, and I retightened the filter, I drove the car normally again. It cost me $60, but the reassurance that there were NO OTHER LEAKS was worth every penny paid.

Alternatively, you can just drive it at 5500 RPM, assume it's nothing major, and maybe starve the engine of lubrication. Eeek! Thus, I'd get it handled and cease your driving-type investigations until you know the root cause.

As you know, oil leaks can occur:

Around the distributor gasket
Around the dip stick
From work around the valve cover - i.e., from re-using an old gasket...and numerous other places.

The problem is obviously not a 'one off' affair. It's not like it's happened for 10 minutes and never happened again. Instead, it is recurring and therefore potentially dangerous.



[ This Message was edited by: Rick MacLaren on 2002-07-24 03:52 ]

[John H]

I concur with Lars - sound slike valve seals. If you back off and coast for a few hundred feet and then floor the gas do you get a really big cloud of smoke.

The other case could be a set of faulty seals in the turbo. I had this once at idle when there was little pressure in the exhaust system the oil would seep pastthe seals and start burning in the turbo. Once you had the revs up the smoking would disappear. An interim fix was to run the car gently on leaded gas and mineral oil for about 600 miles. This caused a slight build up on the seals but hard driving eventualy burn this off and it started again.
The cure was to remove the turbo and rebuild with new seals.

[larso]

John did this turbo seal problem also show smoke when going down a hill? I would be interested to know before I change the valve seals.

[John H]

The smoke normally appeared while you were idling at traffic lights obviously more noticable while you're sitting still.

From memory I think it also appeared when you were coasting nad no load on the motor - sort of gave the same sypmtoms as worn valve seals. It's really testing the memory as this was in around about 1990/91 - I distinctly remember the smokning at idle, as it also appeared while sitting on the grid at the race track. This was why I put my original turbo back on, as I was having to start of the back of the grid due to the smoke.

[wdb]

smoking while idling usually means your rings are worn and not scraping the oil off the cylinder walls

[John H]

True - bu tin the case of the K26 turbo it also means that the seals in the turbo are shagged and letting oil through into either the compressor or turbine side.
If I had not recently changed the turbo for a GTS unit just before the smoking started then I would have diagnosed faulty rings or valve seals.
But as I had only changed the turbo and it hadn't smoked before and it started smoking on start up we knew it wasn't rings but associated with the turbo.

When the turbo was stripped and rebuilt it was found the seals were faulty and the KKK agent in New Zealand paid for the rebuild and also paid me some money for the time it took me to remove the faulty unit and reinstall the original GT turbo

[clhughart]

I am crazyme17's Dad, otherwise known as the little mechanic that goes along with this German car. (Personnally, I have been under the car much more than I have been in it.) We had the head rebuilt at a machine shop and we gave them actual Porsche valve seals. The shop tore up one of the new ones but they replaced it also with original Porsche parts because he had bought an extra one and it he still has the package with the extra one. He replaced 4 of the valve guides and said the others were OK. I really kind of doubt that the problem is valve seals unless there is some kind of trick in getting these in a proper position. The turbo itself was rebuilt by a turbo shop probably around 10,000+ miles ago so it really shouldn't be bad either. I checked on another turbo from R&R in Akron Ohio, around $550. We hate to replace it if that's not the problem. Plus, they said it is only the core (center part) of turbo. I have the following questions:

1) I have never seen a PCV valve but there is a tube that runs from the valve cover (where a PCV might be on a "normal" car) that goes to the turbo. What is inside that part where it goes into the turbo and could this be a problem? (If we get a new turbo from R&R, this part would not be replaced, so we could still have the same problem.)

2) I'm writing this from memory since the car isn't here right now, but there is a canister on the drivers side that has one hose going to the air cleaner, one going to the oil pan (I think it is a drain hose?) and the third hose I don't remember where it goes. Is there anyway this could be related to the problem?

3) I know after the engine was rebuilt that we were getting some blowby, because oil was in the air filter assembly, which had to come through that hose mentioned in the above paragraph. It just seems odd to me that we would be getting that much blowby at deceleration if the rings hadn't seated yet. Looks like it would smoke bad when accelerating hard like most cars do, or does the turbo keep the pressure in the cylinder high enough to keep the oil away from the combustion chamber.

4) We did use crome rings, and the machine shop honed the block. What is our option if the rings never seat? Would a compression check be low if rings hadn't seated?

[Rick MacLaren]

To my knowledge, a compression test, or a leakdown test, might show loss if the rings didn't seat, yes. What color is the oil? Any particulate?

Were these rings by any chance the ones that don't let oil slip down past the piston? If so, they might not be the best choice...

[ This Message was edited by: Rick MacLaren on 2002-08-01 05:39 ]