Smokey!

Car is badly in need of a service however, despite the usual little puff of smoke on start-up, when I'm sat at junctions etc idling at 500rpm, the old girl is smoking away quite happily! Nothing under load or acceleration. Ideas? Apart from knackered coil maybe? Oil seal somwhere? Valve guides? Its in next week for a big service so perhaps its just poor running. Ideas and thoughts from those with technical knowledge appreciated!! (Its a UK TT with full CW decat!)

is this not connected to valve stem seals?

*goes to search....*

Well that was also a possibility. Its just a new problem to add to the list for next week!

Mine smokes on start up but only when very cold.

turbo seals im afraid mate. Mine did exactly the same thing, if you put your cat back on, you'll notice it will stop smoking, because the cat increases the backpressure.

thats why im now single ..

How much we looking for to remedy that baby? Is it likely to be tubby 1 or both? Repairable or new ones?????

Anybody at all??

I'll get me coat!

turbo seals im afraid mate. Mine did exactly the same thing, if you put your cat back on, you'll notice it will stop smoking, because the cat increases the backpressure.

 

thats why im now single ..

Erm, no, I doubt thats right, turbo seals wouldnt leak on idle Im sure. My turbo seal on my no.2 hybrid leaks, and no.2 is usually always the culprit. If your no.1 is leaking at idle, then surely the seal must have disappeared completely, as there is no load on it.....from what I know about them anyway.....

Smoke on startup is your valve stem.......why it would do it all the time ?? Dunno, not techie enough

Why do some valve stem seals leak and others dont, what makes them go, ie non regular oil changes or what ??

EDIT: And you say you have no smoke under load or accelleration, then your turbo seals are fine, they would deffo smoke under load.....

Erm, no, I doubt thats right, turbo seals wouldnt leak on idle Im sure. My turbo seal on my no.2 hybrid leaks, and no.2 is usually always the culprit. If your no.1 is leaking at idle, then surely the seal must have disappeared completely, as there is no load on it.....from what I know about them anyway.....

 

 

Smoke on startup is your valve stem.......why it would do it all the time ?? Dunno, not techie enough

 

Why do some valve stem seals leak and others dont, what makes them go, ie non regular oil changes or what ??

 

EDIT: And you say you have no smoke under load or accelleration, then your turbo seals are fine, they would deffo smoke under load.....

Well thats what mine did, and thats what is was.

theres a thread on here, from a good 6months back, where someone, with a black uk spec, was having a similar problem. Toyota, of all people, told him that it was his valve stems, they did them. And it still smoked, turned out to be the turbo seals.

It could be either or to be honest, its very hard to diagnose, but im only giving you my opinion from my experience.

Put the cat on, if it stops, its your turbos. If it doesnt, its your valve stems.

Well thats what mine did, and thats what is was.

 

theres a thread on here, from a good 6months back, where someone, with a black uk spec, was having a similar problem. Toyota, of all people, told him that it was his valve stems, they did them. And it still smoked, turned out to be the turbo seals.

It could be either or to be honest, its very hard to diagnose, but im only giving you my opinion from my experience.

 

Put the cat on, if it stops, its your turbos. If it doesnt, its your valve stems.

Well I guess you learn something new every day......

Your turbo seals then must have been seriously shot, but surely they would have smoked even more under load though, for them to smoke on idle and not under load just doesnt seem to add up.....??

heres a few threads on it if anyones interested, my original, and another, opinion vary but same conclusion in end...

Linky

Linky 2

Thanks for all this - car is now at my trustworthy specialist in Nottingham where its going to get a full compression check plus other checks before anything is removed and replaced. From reading through the old threads my novice diagnosis is turbo seals (although it was boosting to 1.1bar on the way to the garage - he asked me to check). I've had smoke at start up for a while and with 82k on the clock (plus a full decat) put that down to stem seals anyway. Either way I won't be seeing my girl for a few weeks but she'll be as good as new when she comes back! I feel naked without her!!!!

Yep, turbo seals.

Its the piston ring seal on the exhaust side that weeps and produces the smoke.

When designed by Toyota the exhaust back pressure helped keep the oil from escaping from the turbo. High oil pressure inside the turbo and high exhaust back pressure = little pressure difference for the oil to try to escape.

Once the back pressure is reduced the high oil pressure in the turbo housing and the low exhaust pressure = high pressure difference that the oil is trying to escape into.

At part throttle (low or no boost) and medium revs the oil pressure is high and back pressure very low. The oil will seep out past the piston ring into the exhaust housing. As you're driving along this may not be seen, but at idle it will continue to burn off.

The answer is new turbo turbine side piston rings, which will stop the oil leak for a while; or an even better answer is twin piston rings. This will cure it completely.

I believe the twin ring mod is available from some hybrid builders?

Thanks for all this - car is now at my trustworthy specialist in Nottingham where its going to get a full compression check plus other checks before anything is removed and replaced.

Hope it all goes well fella, who did you take it to, UPAuto?

Whoa, I'm going to have to step in here...

Yep, turbo seals.

 

Its the piston ring seal on the exhaust side that weeps and produces the smoke.

Piston ring seal?! Not sure what you mean here, piston rings are the gas seal rings around the pistons, if they ever reach your turbo you've just blown your engine

I think you mean just the exhaust side turbo oil seal?

When designed by Toyota the exhaust back pressure helped keep the oil from escaping from the turbo. High oil pressure inside the turbo and high exhaust back pressure = little pressure difference for the oil to try to escape.

Hmm, well, oil pressure varies a lot depending on load and conditions but it's usually between 40 and 80psi I think. You'll never see past 30psi backpressure in the exhaust, and at that point the oil pressure is going to be at it's highest, so "little pressure difference" is more like "50psi+ pressure difference". The relationship between oil pressure and boost pressure is very non-linear so I doubt it's taken into account when speccing up the turbo seals. Really it's just worn ones, and when the oil pressure is high during heavy engine load, they seep oil out.

At part throttle (low or no boost) and medium revs the oil pressure is high and back pressure very low. The oil will seep out past the piston ring into the exhaust housing. As you're driving along this may not be seen, but at idle it will continue to burn off.

The lifespan of oil in the exhaust housing is rather brief. I don't think it can hang around in there, there must be a constant supply of oil to burn off at idle.

The answer is new turbo turbine side piston rings, which will stop the oil leak for a while; or an even better answer is twin piston rings. This will cure it completely.

 

I believe the twin ring mod is available from some hybrid builders?

New turbo oil seals is a good idea - all part of a full rebuild. Again, "piston rings" is a misnomer. Twin seals sound bizarre, this sounds like one of those USA fixes like springs on wastegates and drilling holes in oil pumps and stuff - hiding the symptoms rather than fixing the problem.

Anyway, putting the cat back on will show up if it's weak turbo seals or valve stems...

-Ian

New turbo oil seals is a good idea - all part of a full rebuild. Again, "piston rings" is a misnomer. Twin seals sound bizarre, this sounds like one of those USA fixes like springs on wastegates and drilling holes in oil pumps and stuff - hiding the symptoms rather than fixing the problem.

 

Anyway, putting the cat back on will show up if it's weak turbo seals or valve stems...

 

-Ian

Ian, Im having my Hybrids rebuilt in the next couple of weeks through Mark Kindell (if you remember him) and he has someone that only he would use for turbo work, and this chap also said about using double seals. Im a little concerned by your point of saying this only masks the problem and doesnt solve it, but lets say due to a crap build in the first place, hence my no.2 seal now leaking, what problem could I be masking by having a double seal put in.

Also by putting a cat back in how does this show up any weaknesses or valve stem issues, I thought it showed up when you removed the cat due to less back pressure against the turbo seals....??