Smoke at idle

[Toby 200sx]

Just wondered if anyone had any ideas? I'm getting smoke at idle, only when the engine is hot, its definately oil!!
Its been suggested that its a one way valve problem, what is this one way valve? where is it? and how is it fixed?
Thought it might be rings but surely it would be doing it at other times and not just at idle? Have just fitted a mongoose exhaust and i'm told the one way valve thing is very common after fitting one. Please help as i don't want to go rebuilding my engine if its not neccessary.....
Thank you
Toby

[shebban]

I hade same problem. It was the turbo that needed to be changed! The oil rings inside can not hold presure when car is idle. Or it can also be oil seals arownd your vaules.

[shane]

Try a one way valve. Take a trip to a local scrapyard and find a car with a decent sized engine. Look for the hose from the brake servo to the engine, threre should be a small valve, remove it (take some of the pipe). Check the valve (you should be able to blow through one end and not the other). Fit the valve between the engine breather and the air intake. The valve must allow the engine to breathe out but not suck in.

(picture borrowed from a previous post)

my one way valve is on the pipe as it exits the engine to the catch tank (old picture).

Later pic below showing recent breather setup. A oneway valve would be fitted in the pipe to the catch tank.

[PrimeraRacer]

can you just confirm exactly how it needs to be fitted and an explanation of how it works etc.

I'm looking at your picture and seeing that its placed in the middle of the breather that goes from the engine to the intake. exactly which way round does it go and how does it work to stop the smoking etc etc.

Many thanks
Kev

[shane]

Not sure excatly how it works, but from my basic knowledge when the turbo isn't boosting the vacuum draws in a small amount of oil through the gaskets which burns creating the smoke. The oneway valve lets pressure out of the engine (very important) but doesn't allow air to be drawn in through the outlet to the intake, thus stopping the letby from the gaskets. (somebody please correct me if i'm wrong ). The fitting of the valve is in the description on the thread.

[ADON996]

Just chop the pipe and put your one way valve in so it lets the air go from the head to the airfilter intake pipe. does the trick even when my turbo was fookd for a while

[Jonny Wilkinson]

Looking at what's been said and the excellent pics, it looks to me like this is what is happening....

There are free-flowing breather pipes connecting the plenum, the head (cam-side) and the air intake.

The purpose of the breather is to allow equalisation of pressure in the head by blowing excess pressure through the breathers to the air intake. This can allow a small amount of oil into the breather pipes as there is oil flying about in the head

When the engine is on the overrun, a vacuum occurs in the plenum allowing air to be drawn from the breather pipes into the plenum (with a bit of oil in it). The air taken from the breather pipes is replaced by fresh air from the air intake.

The oil then gets burned as it goes through the cylinders.

Fitting the one-way valve in the pipework to the air intake would stop air being drawn in which would massively reduce the amount of air that could be taken from the breather pipes into the plenum.

Does that sound even half-right ?

[Paul FWx]

Deffo seems a turbo problem to me, my last two have had the same problems

[Jonny Wilkinson]

Sorry, Paul. It's a bit of a thread resurrection on my part as the thread has been made sticky.

I'm interested in the one-way valve thing coz I'm getting a brown oily deposit on the rear bumper round the exhaust and I was thinking of trying the valve before replacing the seals on my turbo as that seems the next most likely source of the oil.

[.G.]

Yeah i went to look at the car as he was selling it. he said he just cleaned out the breather's didnt seem to be smoking altho it was dark.