924Board.org

[Carrera]

Anybody ever experienced turbo whistle on a 931?

I thought it was a vacuum leak that was causing the turbo whistle. The vacuum hoses on my car were really crappy with DYI tape fixes all around. The hoses have now been replaced with Dan’s vacuum hose kit. Thanks Dan for providing us with these ready made kits
Just noted that the elbow from recirculation valve is NLA and therefore not included in the kit. Anyone have the part number for this so I could locate it easier from PET?

Also the exhaust manifold and the J-pipe were investigated as they are prone to cracking. No cracks found, however the ends of the J-pipe had corroded causing the seals to loosen up and there was evidence of a leak. The J-pipe has now been cleaned and fixed with new seals. And as the wastegate bolts were of course stuck, the wastegate came off and was broken into pieces and thoroughly cleaned.

The whistle is no longer as loud as it was before but it’s still there. However, from the seat of my pants I can’t tell it having any effect on power. It’s just damned annoying…

My friend who does most tech work on my car suggested it could even be the blow off valve that I guess is somehow built into the turbo…? The turbo itself was also inspected and there is no excess play…

Another thing is the smoking after a cold start. At start up the first minute is just fine. Then comes the blue smoke clouds… And after a short drive they disappear and the car does not smoke on idle when warmed up… Valve stems or just seals?

Thanks for any pointers!
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931 S2, 1981

[Raceboy]

If you suspect a vacuum leak, take apart the by-pass valve on the turbo and inspect it. If the spring is worn/broken etc the bypass will leak and it causes turbo to do excess work in order to maintain boost pressure specified by wastegate. Also you could hook up the boost gauge to measure boost pressure.

Regarding smoking, it points to the worn turbocharger (oil seals are shot).
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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[Carrera]

Thanks Raceboy for the pointers!
Does the turbo need to come off to inspect the by pass valve or is there a way to tell without a huge work effort?
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931 S2, 1981

[Cedric]

I had some severe whistle one time, located it to some really bad threads at the joint between the charge pipe and the pipe after the turbo. Check that joint. Redid it with helicoils and its been tight since, even though I have taken it appart several times.

I also had problem with a stuck pop off valve, the boost just dissapeared. Couldnt hear the light clunking sound from the valve when i stod at the engine and reving. So i took it appart and found the old rubber gasket smeared all over the pop of piston wall. Bought a new gasket from (Seemed like different material) porsche for not big money and it was up and running again
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1980 924 Turbo
www.instagram.com/garagecedric/

[Carrera]

Thanks Cedric!
I'll need to check that joint.

How is the by pass valve set up in the 931? Can it be fixed without taking out the turbo?
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931 S2, 1981

[Grenadiers]

I took one apart while it was in the car. There are two gaskets, one on each side, if you can't find any, I have a pair I don't need that I can send to you. One side is easy to remove, the other side butts up against the front frame rail. Remove easy side first, removing spring tension, then remove bolts on frame rail side. Fix that side first. Was about 4 years ago I did this, so buyer beware~!
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'83 944 Track car.
'88 924S Track car.
'89 944 Turbo
2004 Winnebago Vectra monster RV
2012 Jeep Wrangler
2014 Kia Soul
2001 Ford F350 powerstroke

[9xx]

[Carrera]

[9xx]

Hmm, are sure that the mesh part is also clean? It doesn't necessarily help if you clean the oil catch can and related hoses, you have to clean the mesh too. It is connected to the engine block itself. The location is quite difficult, of course.

But if it's clean, then it's clean.

Another question is that how normal is it for a 931 to smoke on a cold start? Certainly not unheard of.
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Mikko

All gone: 931 '82 Alpine White, original option "220" G31 with LSD + 3 x 944

[jessy1984]

hi

i was looking at this post and seems to be a verry simmiler problem that i have with my own 924turbo ( US car )

when i start the car everything seems good
then after not 1min it starts to smoke verry bad
when engine is hot the smoke dissapears

now the engine is completely rebuild also the turbo
real strage as i have spend a lot and the car is sitting in the garage now cous i cant get it to run properly

when i saw this post i hoped for a solution but still nothing at this time
is it solved alreddy ?

[bear924]

Back in 2000 my car would start to smoke really badly when it came back to an idle. If I stopped at traffic lights it would smoke, more of a white smoke from what I can remember. In my case, a replacement of the turbo seals fixed the problem. You problem sounds more like the valve guides to me. (which I replaced when trying to fix my problem (before the turbo)).

[Carrera]

It can be either the turbo seals or valve guides and if its really bad it can be the piston rings. In my original case I'm putting my money on the turbo seals. I have a set of seals from Dan waiting for the right moment. As long as the problem is not horrific I can live with it as the turbo disassembly, rebuild, reseal, assembly show takes a couple of days and costs €€€ if you can't do it yourself... Let's see, I might sell the car before it really needs a turbo rebuild
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931 S2, 1981