Friend's V8 is smoking

[superdavelotus]

I have a local friend who has a V8 which had a rebuild recently. It started smoking now and then mainly on decelleration but only once or twice then nothing for a day or so. Sometimes he can go a week then it starts to smoke? He changed one of the turbos because it had end play but it didn't make much difference then he changed the other. Smoke went away for a few weeks but now it's back again. He's also changed the oil several times and tried difference grades of oil etc.

He's now running out of ideas?

It could be the turbo he's just had rebuilt or something internal?

If internal, why isn't it happening all the time?

He's not on this forum or the internet so he's asked me to ask the question.

David Walters

[ramjet]

Grey, blue or black smoke?

[910Esprit]

Smoking on overrun (deceleration) is typically a sign of valve guide wear or seal failure. The engine is pulling maximum vacuum as the throttles are closed, so it drags oil down the guides.

Having said that, you would expect that to be consistent, which isn't this guy's experience.

[superdavelotus]

I am guessing it's blue smoke because if it was black (rich) or white (weak or head gasket or water based) then he would be looking elsewhere. With dreaded blue smoke, we fear the worse. I hoping it's his turbo that hasn't been rebuilt properly.

It does seem odd about it being intermittant, I've never seen this before. I've only seen his car smoke once and I've seen it about 4 times now.

David

[ramjet]

Steve,

The amount of vacuum though would be dependent on the rpm prior to deceleration and whether David's mate lifts off the loud pedal completely. That may account for it being sometimes and not all the time. Lot of variables.

David,

Is it one bank or both?

Edited September 29, 2009 by ramjet

[Advantage]

Idling after a hard run, does it start to smoke then? And as above, one or both sides?

[Günter]

how's the oil level in the air-cleaner housings ? how much oil did the engine pump into that system.. .?

[th4neuk]

On a side note is the oil level ok??

It might be it has been over filled which has to get out somewhere maybe??

Cheers

Alan

[Che]

"Idling after a hard run, does it start to smoke then? And as above, one or both sides? "

A sign of a turbine oil dripping through the exhaust.

On cruise or on boost, no smokes.

On idle or decelleration, smokes ---->means turbo oil issue.

[superdavelotus]

Hi all,

I don't know all the answers so I'll ring him in the morning and find out. It's tricky working out which side as it's not necessarily the side coming out the exhaust is it? Does it depend what type of exhaust back box you have? I think he has standard and it ws coming out of both but one more than other.

I will try and find out as much as possible but from what he's told me already, there isn't a set of things he does or the car does which makes the smoke happen. I will check tomorrow.

David

[Advantage]

I'd wager 16 pence that one of the turbos has gone phut.

[Günter]

standard box: - as the endpipe goes from left to right, undo the inlet and watch out which one is oily/dark black.

sports-box : -every side goes its own way, there is no mixup on the endpipes.

If you want to determine if it is oil from the turbos: undo the turbo inlet ducts, and watch out for oil -is there much oil watch out if it comes out of the air-cleaner housing [as the crankcase breather ports are there]. Is there not much oil, bud there is fresh oil on the catalyst pipe: the turbos are leaking. Is the turbo not oily, bud an serious amount of carbon deposit/buildups on there: the engine burns much oil -that comes probably from elsewhere (piston -blow by, valveguides or what ever..)

As others have mentioned -that are all just some thoughts.. .