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Lots of blue smoke


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Hi all,

I'd appreciate some help to solve the problem I'm having: Our '98 300 TDi (170,000 miles) runs well overall. There is some blue smoke after a cold start, but that clears up within a mile. However, if after driving in slow traffic, it will start to blow lots of blue smoke, so much that other drivers start gesturing. This has been happening now for some months, and it is getting worse.

Once I even saw sparks (and a flame) out of the exhaust, while not pushing the car hard at all. I don't think it is heat related, it happens with both a cold and a warm motor. After a while of highway driving, the blue smoke goes away. Turbo seems to be fine. There wasn't a lot of oil in on the high pressure side of the turbo.

We do have some pressure under our oil filling cap, just enough to keep it up in the air a bit, but the stick has never been blown out. Air filter has been changed. Car doesn't run on its own, so I don't think there is oil blowing in from the crankcase.

A good mechanic replaced the head gasket as a first guess, but that didn't help. He saw some wear on the cylinder walls and has suggested honing them.

I'm puzzled by the fact that the problem only occurs after running stationary or slow driving. Any ideas? Would bad piston rings cause such a problem? Any suggestions what to check?

Klaas

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You may have an oval bore.

Rings may have gone.

Valve steam oils seals may have gone (but unlikely)

Check Turbo for excesive movement, about 1/2 a mm up and down but shouldn't be any in and out.

You said you've seen wear on the cylinder walls ! you should still see the original honning marks, if not yes wear is there.

Good Luck.

Nick

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