924 turbo - smoking

[johntom]

hi
i have just bought a 1981 924 turbo (series 2) which blows out light blue smoke above 3000rpm !

I have removed the plugs and all 4 are black and oily, how do I tell if it's the turbo, the ring, bores or the head/valves ? or could it be something else ?

[vdubr928]

Compression and leakdown. But sounds like turbo.

[924RACR]

Yeah, what he said - compression and leakdown.

Noting that the boost comes on around 3000rpm, it would seem you have a boost-related oiling problem. Given that it appears to be bringing oil into the combustion chamber... the oil should be coming in in the intake tract. Very likely seals leaking in the turbo, but do the leakdown first to make sure the basics are good. Then to line up a turbo rebuilder; it's not easy to remove the turbo with the engine in, but will save a lot of money if you can just send out the turbo.

There's lots of guys in the UK on the 924board.org - one or more can probably recommend a turbo rebuilder.

These cars do also tend to have the valve seals harden up and leak with age/heat... but those are different symptoms...

Congrats on the purchase!

[wild man]

Without water cooling (and turbo-timer w/electric WP), those turbos run real hot. That means that the seals will have a relatively short lifespan. The factory learned a lot about this issue, from that particular model. This is evidenced in the next turbo model of the FF (front four) series in 1986. They definately switched-up and went all-out on turbo cooling there. And they weren't concerned about the complexities involved in making that happen.

That does seem to be their M.O. when it comes to most issues though. They aren't afraid to use complexity as a means of solving issues. But that may have been what killed the series. Do hear "over-engineered" (especially the FFT)? With complexity comes not only higher initial cost, but also more things to go wrong, meaning more repairs, which also cost more because they take longer due to more OTHER things needing to be removed.

[Rasta Monsta]

Gotta disagree with the above. With proper cooldown, the seals last just fine. The 951 setup was employed to avoid a common operator error. . .shutting down red hot.

[johntom]

Thanks guys

I have a compression tester but will have to find someone to carry out a leak down test.

So if i understand this right, the turbo is forcing oil (from it's own lubrication system- the feed and return pipes ?) through the intake and into the combustion chamber ?

if so would I be able to trace and see the oil path to confirm this ?

[Rasta Monsta]

The turbo CAN spit oil into the intake, and into the exhaust. One clue in your case is your fouled plugs.

These cars also tend to break rings, and if you have excessive blowby, the turbo seals won't work regardless of their true condition.

[vdubr928]

Originally Posted by johntom

Thanks guys

I have a compression tester but will have to find someone to carry out a leak down test.

So if i understand this right, the turbo is forcing oil (from it's own lubrication system- the feed and return pipes ?) through the intake and into the combustion chamber ?

if so would I be able to trace and see the oil path to confirm this ?

No. But you will probably see excessive oil in the intake after the turbo, rasta is the expert and helped get my 931 going so let him check my work here but, the idea is, you test for leakdown and compression. If those test are good it is not likely to be an issue with blowby or valve leakage. This really only leaves two possible sources for the oil. The head gasket, which has in my mind been eliminated because you stated all the plugs were fouled (also probably eliminating a broken ring as all cylinder are effected) this leaves the turbo. Added to the evidence is the fact that it happens around the same rpm that the magic really starts to happen in the turbo. Blowby tends to be worse when you let off the gas, increasing vacuum in the combustion chamber.

It doesnt look good for your turbo but its worth doing the compression and leakdiwn test.