turbo or valve stem oil seals?

[bo!]

I have a leon cupra 180 AUQ stage 1 .
the car is puffing blue smoke out of the exhaust .has done for around two years it used to do this occasionally on cold starts after being left over night .
but I recently put a 3" decat downpipe on the car and now the smoking has got considerably worse .but the symptoms have changed..it does not smoke on cold starts any more .the symptoms now are when the engine is hot !.it smokes on idle .also if I pull of from a set of trafic lights after long durations of idling if i touch the throttle il get a puff of blue smoke . It doesnt do this on overun .i have had a compression test about a year ago and all was ok .i recently took my tip off the turbo to check the shaft for play and there wasn't any side to side movement but there was some minimul in and out play.i have read tons of threads on blue smoke & burning oil but the ones where people have changed turbos and the symptoms persists never seem to get to the bottom of it .and the threads end .I have not yet changed my turbo but I also dont want to change it and find out the symptoms persist .I now I am going to have to bite the bullet sooner or later .but I am looking for some guidance .so what is the general consensus from those in the no as to where I go next .????
all input is greatly appreciated .

 

[bo!]

Forgot to mention it doesn't smoke on boost.

 

[Ryan6926]

Have you got any fault codes coming up?

I'd suspect you're likely to have some now because of the decat but if you'd checked before it may have given you Lambda faults,

Is it burning oil or anything that you've noticed?

 

[bo!]

Hi no fault codes . I used a lambda spacer on the decat.defo burning oil blue smoke and stinks of oil .it doesnt happen all the time but most of the time now .

 

[wildrides]

Take the turbo off and fit a new oil control ring behind the hot side turbine .......... they sell them on ebay separate or in a kit with all the bearings as well ( kit about £ 100 genuine oem )

Remove intercooler and drain all the leaked oil out and wash . If your not capable of above just send the turbo off to beach buggy or who ever for a rebuild ( they use the same kit and charge about £250 ) It you do it yourself be aware the compressor nut is left hand thread normally . It is not difficult but requires an amount of patience and care on reassembly . You need to mark the orientation of the compressor wheel and turbine wheel on the shaft, as they need to be returned in the same orientation so that the core unit retains its OEM balencing . If you dont do this the turbo will whine like an angry housewife and its life will be 5oK instead of 100 K before the next rebuild.

When you have refitted the turbo rag the car for a few weeks to burn off all the leaked oil from the exhaust etc.

If it still smokes you need to change the valve stem oil seals ........ this can be done without removing the head but perhaps best left to an experienced person .

If it still smokes after that AND you run a crappy cotten filter that you can hold up to the light and see daylight through AND you live in an area off low rainfall with dusty roads you will have scratched bores and worn piston rings from road stone dust inhaled into the engine . This will also show as heavy wear on the compressor wheel in the turbo.

 

[bo!]

Thanks for the reply wildrides .
so a turbo that does not smoke on boost at all could still be faulty .?car still boosts fine 1.4bar before tailing off higher up the rev range.and the filter I use is not very old so that's ok.

 

[wildrides]

Correct ............ boost pushs oil back into turbo body .............. no boost allows oil to leak past oil control ring and into exhaust WHEN there is little pressure in the exhaust .... and conversly back pressure in exhaust stops it smoking ( it looks just like a miniture piston ring and does wear out eventually ) A sign is that your engine oil goes black very quick after an oil change when before it used to stay golden coloured for several thousand miles ( exhaust gas getting past the turbo oil control ring changes the colour of the oil quicker than normal )


valve stem oil seals smoke only after a period of non use ie over night . The oil runs past the seal over several hours and burns in the combustion chamber on start up . sign of worn stem seals is :- let car go down long hill off the throttle . Hit the throttle at the bottom of the hill ........... if cloud of blue smoke for several seconds then clear = valve stem seals . On the overrun during the engine braking phase there is a vacuum in the combustion chamber which sucks oil past the worn valve seal or piston rings . The oil then gets burnt when you get back on the gas pedal .

I would get the turbo done first as that is most likely of the two

 

[bo!]

It did used to smoke on cold start after being left overnight .but it hasnt done this since fitting a decat a month ago.if left for a 3-4hours it can chuck a puff of smoke out the rear though. The symptoms now are only when engine has been warmed up .As for engine breaking I can take my foot off the gas coast then back on the gas and a puff of smoke comes out the rear .I thought that could have something to do with the back pressure on the exhaust side of the turbo though? . Also After a good thrashing it smoked more on idle.I had the intercooler off not long ago there was no oil in there .boost pipes are clean and I took the tip off last week where there was a bit of lateral play .is there anything else I can check or get checked whilst I sort my finances out . lol!!!.

 

[wildrides]

How many miles has the engine done ?
How many miles has the turbo done ?
Is the car running standard PCV system ( crankcase ventilation ) or modifications and a catch tank for oil vapour ?

if there is no oil in the intercooler then the coldside of the turbo must be in good shape . Side play in the shaft is normal and this is taken up by oil pressure, thus as long as the compressor wheel does not touch the snail housing when you test the play and turn it at the same time thats ok.
Normally you will get some oil in the intercooler when running stock PCV so I am assuming as you are not that you are running mods with a catch tank . If the car is old and high milage then that might point to Valve stem seals however I would still favour the oil control ring is worn out on the turbo hot side. If it goes completely one day you will get a cloud of continuous dense white smoke behind you and quickly empty the sump ......... time to stop . But could go for ages before that happens

 

[wildrides]

Ps
forgot to mention change in symptoms after de cat

:- when cat is fitted it takes a few minutes to reach working temp and after that pollution ( oil ) gets harmlessly burnt . Before it gets hot oil smoke gets through and shows at the tail pipe. After a few minutes driving cat is working and that stops happening.

After you remove cat nothing takes out the oil smoke so it smokes on start up and keeps smoking all day cos the cat is not taking out the smoke any more . This is why you need a cat to pass the MOT basically .

 

[bo!]

The car has done 122k.
turbo mileage unknown.
Pcv is stock.crankase ventilation.
The turbo play was if I pulled it in and out .
blue smoke on cold start was when I had a cat it Hasn't done this since fitting the decat. symptoms only show themselves after the engine gets hot.
I have heard of stem oil seals only showing themselves when the car gets to temp is this the case?

 

[wildrides]

No ........... stem seals usually smoke after a sustained period of engine braking when hot or cold . tell tale 2-3 second blue puff when back on gas . If it is a jet black puff after a hot thrash the sensors before and after cat have got a bit hot causing the ecu to make a rich mixture to cool things down. At your miles it could be stem seals ........ they tend to get a bit brittle and stiff with age and the liittle springs on them cant close them on the valve stem as effectively as before . I am assuming here that you are using the correct viscosity oil in the engine and that you have not over filled it . You may just have a score down one cylinder . I had an engine once that used no oil what so ever between services until 98k when it suddenly started using a litre every 5000 miles . Naturally I stripped turbo and rebuilt it although all appeared ok . Ditto with the valve stem seals . It carried on using exactly 1 litre every 5000 miles until at 190k the head gasget went . On replacement of gasget I noticed a score all the way down one cylinder . Car still running perfectly well and at 215k now, but still using exactly 1 ltr every 5000 miles !

point being, you can have a score on a cylinder like that and the oil still seals it well enough to get compression BUT the engine uses a bit of oil and smokes a small amount . And that infact was a diesel engine where compression is vital to make ignition of the fuel happen.

 

[bo!]

Yes im using 5w40 fully synthetic. recently done oil change around 500miles ago .I dont fill it right up about 3/4 on the dipstick I have topped It up twice probably about half a liter since the oil change .the car is doing exactly as you describe 3-5 seconds of engine breaking then it will smoke .or prolonged vacuum like in trafic idle for a bit and then it smokes sometimes worse than others.its at the point tho where it is pissing other drivers of behind me in traffic becouse they are geting covered in oil smoke .

 

[bo!]

Been thinking about having a leak down test on the motor .is it worth having one ? not sure where or how much I should pay ?

 

[bo!]

test results from compression and leak down tests

DRY.
cylinder
1. 2. 3. 4.
11bar . 10.5bar. 11bar 11bar

WET
cylinder
1. 2. 3. 4.
12.8bar. 13bar. 14bar. 13.5bar

carried out a leak down test after on cylinder 2 and 3
Cylinder 2 stayed in the green and held pressure where as cylinder 3 held pressure but we could hear air leaking from the dipstick ??

 

[bo!]

Bump!

 

[wildrides]

Seem ok to me .

why not change the valve stem seals and turbo bearings and seals? ............. its cheap enough parts wise

 

[bo!]

The chap that performed the compression and leak down said the results from cylinder 3 were conclusive of worn rings would you not agree???

 

[wildrides]

change the rings if you want .......... Its just a fair bit more work. Personally I would try the easy stuff first . The figures are not that different are they for the amount of smoke you are getting . It depends how much you think the car is worth and how much you wish to plough into it .

 

[bo!]

Figured the car is not worth the amount it could potentially cost to sort after speaking to a few garages. So I ended up putting the standard cat back on . And now the car is behaving itself .it has give the occasional puff of smoke after being left for a few hours after driving but what ever was causing the smoke the cat is able to burn off the smoke before it exits the tailpipe now because it is not smoking now when driving.