burning oil

[elmof1]

Right got the MOT tomorrow so i need to fix this problem ASAP. Before I rebuilt my car I assumed it the turbo oil seals knackered as it was let oil passe the turbo seals and oil was in the intake pipes and intercooler.

I've just got the car on the road for a quick spin with a brand new turbo and its still smoking on boost and overrun, but Nothing at idle. So some help guys with things to check. Some questions I have.

1) Is there normally a oil restrictor on the turbo oil feed? The one way valve it currently fitted.

2) Could it be a breather issue? I was thinking of puting the breather pipe into a catch tank and see if it fills with oil.

My oil pressure seems fine, sits around 5 on the dash gauge. Anything else you can think of please post here.

[car.crash]

It could be unburnt oil sitting in your exhaust pipe.

[LiamR]

Headgasket possibly?

[SCHWARTZ]

Put the breather to a catch tank, if your engine is breathing heavily it will go through the turbo and into the boost pipes. Take it for a good run after to clear any unburnt oil, if its still smoking and there's no oil in the water its most probs rings.

[SCHWARTZ]

Also check there's not to much oil in the engine. You want it to be in the middle of the 2 marks.:ashamed:

[kentraider]

seems like its the rings to me too

[elmof1]

seems like its the rings to me too

You maybe correct. There is no oil in the intake so I dont think its coming from the turbo, but it does smoke reasonably heavy under boost.:(

[Markey Mark (BD)]

With the engine running on idle remove the oil cap and see if you got alot of pressure coming out the rocker cover, also do you have the standard breather set up in there still?

[elmof1]

With the engine running on idle remove the oil cap and see if you got alot of pressure coming out the rocker cover, also do you have the standard breather set up in there still?

Yeh still running standard breather setup, and there is a valve inside the breather pipe that goes to the back of the intake manifold. Anything there for me to check??

[Markey Mark (BD)]

Yeh still running standard breather setup, and there is a valve inside the breather pipe that goes to the back of the intake manifold. Anything there for me to check??

Thats your oneway valve, it'll run fairly lumpy if that has failed as it'll be sucking in alot of air on idle and leaning the mixture out alot.

As few people said try running the breather pipe going to the air filter into a bottle and see if your getting any oil in the bottle, this will give an idea if the engines breathing. If not time to look somewhere else

[elmof1]

Just looking at the breather system and if I remove the breathe pipe that connects to the back of the input from the the plastic 3 way tee I'm getting quite a bit of vacuume at that point.

Now I've removed the valve from that pipe and it's just a round peice of plastic with a small hOle in the middle: no way will that act as a one way valve. Do you guys think that's the problem??

It does seem a little lumpy on tick over!

[elmof1]

Just looking at the breather system and if I remove the breathe pipe that connects to the back of the input from the the plastic 3 way tee I'm getting quite a bit of vacuume at that point.

Now I've removed the valve from that pipe and it's just a round peice of plastic with a small hOle in the middle: no way will that act as a one way valve. Do you guys think that's the problem??

http://i216.photobucket.com/albums/cc279/elmof2/627f80bb.jpg

[Tony Walker]

Realisticly the tester shouldnt get it on boost anyway so it shouldnt fail. the only fail is for excessive smoke on idle.

[elmof1]

yeah on boost it will force oil through, it should suck oily fumey vapory stuff through when theres a vacuum.
Realisticly the tester shouldnt get it on boost anyway so it shouldnt fail. the only fail is for excessive smoke on idle.

What do you think Tony, replace the one way valve or is the cup breather mod worth considering. Is there a short turn fix, like blocking off the inlet?

[Ian S]

Now I've removed the valve from that pipe and it's just a round peice of plastic with a small hOle in the middle: no way will that act as a one way valve. Do you guys think that's the problem??Yes Renault put that there to cause this kind of issue.


That is a restrictor. There are two of them. You need them there if you have the whole set of pipe. The idea is that under boost, when the inlet manifold no longer sucks, the turbo inlet suction keeps the crankcase it minus pressure. But off boost, the restrictors stop that open end from defeating the inlet manifold suction from the crank case.

The one way valve is a largish metal hexagon on the back of the manifold. There are two there. The other goes to the brake servo canister. They stop boost pressure from leaving the inlet manifold.

The cup mod has nil to do with the oil breather circuit.

[elmof1]

Yes Renault put that there to cause this kind of issue.


That is a restrictor. There are two of them. You need them there if you have the whole set of pipe. The idea is that under boost, when the inlet manifold no longer sucks, the turbo inlet suction keeps the crankcase it minus pressure. But off boost, the restrictors stop that open end from defeating the inlet manifold suction from the crank case.

The one way valve is a largish metal hexagon on the back of the manifold. There are two there. The other goes to the brake servo canister. They stop boost pressure from leaving the inlet manifold.

The cup mod has nil to do with the oil breather circuit.

I was thinking of simplifying the Breather system and blanking off the one way valve, and run the rocker and crank breather to a catch tank?

[Ian S]

Those cup cars had the oil drain cut off above the oil level so pressure leaves via that tube. So they took it to a tank.

The road cars are not like that. That pipe remains an oil drain. Their only crank case vent in on the top of the rocker cover.

Unless you make another from the sump.

Cup cars only raced for a few minutes. And, my guess is they normally had good rings and at only 14 psi, not much blow past or oil to collect.

At 20psi a 5GTT can blow out quite a bit of oil when they're fine at 15psi.

[Tony Walker]

Sry Ian is correct. Its easy enough to block the pipe to the inlet manifold to help see if this is the cause.

[Ian S]

Regarding the problem of smoke on boost.

It's not coming into the inlet manifold though the oil breather as there's either no movement in there, or the one way valve is leaking and is blowing the fumes away back to the turbo inlet, where they'd be sucking into anyway.

If you're rings are worn, which was also my first thought, the excess crankcase pressure will blow oil into the turbo inlet and you'll get smoke.

You can take the breather pipe out from the 'telephone hose', plug the hole in the 'telephone hose', and take the breather pipe to a tank. That will stop that problem.

If there is a lot of blow past, and oil collecting in that tank, you'll need to empty it often, maybe daily. Sometimes you can have, eg, a damaged ring land and the engine will empty litres out into the tank.

[elmof1]

Regarding the problem of smoke on boost.

It's not coming into the inlet manifold though the oil breather as there's either no movement in there, or the one way valve is leaking and is blowing the fumes away back to the turbo inlet, where they'd be sucking into anyway.

If you're rings are worn, which was also my first thought, the excess crankcase pressure will blow oil into the turbo inlet and you'll get smoke.

You can take the pipe from the 'telephone hose' out, plug the hole, and take it to a tank. That will stop that problem.

If there is a lot of blow past, and oil collecting in that tank, you'll need to empty it often, may daily. Sometimes you can have, eg, a damaged ring land and the engine will empty litres out into the tank.

That was my initial thought that oil was being blown into the telephone hose, but all my intake pipes are clean inside, no traces to oil. Thats why im a little confused

[Ian S]

I was thinking of simplifying the Breather system and blanking off the one way valve, and run the rocker and crank breather to a catch tank?I think problem with this is that the lack of vacuum applied to the crank case might help it to push oil past places such as the crank seals and valve guides. Maybe up the bores a bit.

It's a complete certainly that Renault would not have put that lot there if there wasn't a need to. They would have saved the money. Regulations probably dictate that oil vapours should be burnt and not just released into the air. If that's all and not for any leakage problems then from a functional point of view it could all be binned.

[Ian S]

That was my initial thought that oil was being blown into the telephone hose, but all my intake pipes are clean inside, no traces to oil. Thats why im a little confusedWhat, none?!

Well then that points to the turbo oils seals?

I don't know if it's possible that it could be a crack in the bearing casing leaking to the exhaust side??

Or guides or head gasket.

Unless the smoke is water and you've a cracked liner?

[elmof1]

What, none?!

Well then that points to the turbo oils seals?

I don't know if it's possible that it could be a crack in the bearing casing leaking to the exhaust side??

Or guides or head gasket.

Unless the smoke is water and you've a cracked liner?

Well I never thought of that! Its a newly recon'ed T25 unit but I guess its possible. I have a spare T2 Hybrid I could fit?

I'll check the plugs to see if they are black!!!

[elmof1]

Well Ive investigated the problem a little more and number one cylinder has only 85PSI on compression test. Add some oil to the cylinder and its back up to 150PSI.

Also run the car with a catch tank on the breather and it collected about 20mill of oil but also looked like some water mixed in; check the dip stick and the oil looks clean.

Intake pipes are all still nice and clean inside, no traces of oil

[Ian S]

No 1 (the water pump end) is often the one that gets scored, liner and piston sides, if the piston expands during extended high load, ie, a long time on full loud pedal.

So it rather looks like blow past is pressurising the crank case and even though the breather and inlet hoses look clean, that's the source of the smoke.

Or could it be the head gasket and that leakage is making it's way into the oil and water ways?

That wouldn't be valve seats would it that a splash of added oil would temporarily seal?

I know this is stating the obvious but either way, it kinda looks like the head has to come off for a visual inspection of those parts.

[elmof1]

No 1 (the water pump end) is often the one that gets scored, liner and piston sides, if the piston expands during extended high load, ie, a long time on full loud pedal.

So it rather looks like blow past is pressurising the crank case and even though the breather and inlet hoses look clean, that's the source of the smoke.

Or could it be the head gasket and that leakage is making it's way into the oil and water ways?

That wouldn't be valve seats would it that a splash of added oil would temporarily seal?

I know this is stating the obvious but either way, it kinda looks like the head has to come off for a visual inspection of those parts.

Yeh head off is the next job. I'm moving house next weekend so i'll keep it together till I've moved then strip the head off to have a look.

I'll probably do a semi-rebuild, check liners, and re-hone or replace if required, new rings, big end bearings, head gasket.