Your thoughts please - oil burn after long idle

[JohnM 855 T5R]

Hi All,

Yesterday I was in my T-5R when I was held up at some complicated 4-way traffic lights that caused me to sit idling for around 5 mins. When I pulled away there was a BIG cloud of oil smoke from the exhaust which cleared very quickly. Thinking about it's, it the first time since I bought the car last August that its had a prolonged idle.

To give you some background:

It's just on 1800 miles since an oil change and judging by the dipstick its used around 300ml of oil = 6000 miles/litre. Oil is 5W/40 full synthetic Castrol Edge (which I've used in all my high mileage T5's going back to 2005 and is Volvo recommended nowadays so please, lets not get into the synthetic Vs semi synthetic argument and keep this thread on track. It's nothing to do with the 5W cold rating either - we are talking about a thoroughly hot idle where its the hot viscosity rating of 40 is all that matters). Also, the PCV is fine and doing it's job.

So, given that it's doing 6000 miles/litre and there is no evidence at all of smoking either whilst normal running (I've had someone follow me to check) or after a short idle what are the likely culprits or such an oil burn. I can only think of these possibilities and these are my views

1) Worn rings/ liners - not a chance I feel. Smoking would be general and consumption way higher. Besides, the engine pulls like a train.

2) Valve guides or valve stem seals - I think it's very unlikely. Oil bypassing the seals/guides would be burnt straight away as it finds it's way into the combustion chambers with, at worst, a puff of smoke when pulling away (this wasn't a puff - it was a big cloud) - and again, consumption would be high.

3) Turbo oil seals - this I feel is most likely. If the seals are on their way out, there could be some pooling of oil at idle in the turbo assembly which gets thrown out as soon as the turbo spools up and burnt either through the combustion chambers if leaking on the pressure outlet side or in the hot exhaust if on the exhaust side (more likely).

I would welcome your thoughts on this.

Furthermore, has anyone recommendations as to a good turbo re-conditioner who gives a decent warranty (and who can rebuild my 15t as a 16t if I chose to).

Thanks all.
John

[john.wigley]

My late Ph1 V70 is prone to this too, John. I have no turbo so can't comment there, but being an N/A engine, I strongly suspect my valve stem seals. This is apparently not uncommon as mileage accumulates (my car is now on just over 130K). My garage agree, and have advised me to live with the problem unless it becomes too troublesome. As I'm doing very little mileage now, and would find it difficult to justify the cost of replacement, I'm inclined to agree. The car also exhibits similar behaviour upon first opening the throttle, following a long descent on the overrun.

Regards, John.

[JohnM 855 T5R]

Originally Posted by john.wigley

The car also exhibits similar behaviour upon first opening the throttle, following a long descent on the overrun.

Regards, John.

Thanks for your input John. I don't have the problem after a long descent on overrun - but then mine is an automatic so it drops to idle revs on overrun which would mean a bit less suction to pull oil through. Do you have any idea what your oil consumption is?

Regards
John

[john.wigley]

Originally Posted by JohnM 855 T5R

Thanks for your input John. I don't have the problem after a long descent on overrun - but then mine is an automatic so it drops to idle revs on overrun which would mean a bit less suction to pull oil through. Do you have any idea what your oil consumption is?

Regards
John

My car is also an automatic, John, and, yes, the revs do drop to idle on the overrun - but isn't that the same as during your extended wait at the traffic lights?

My oil consumption varies. If I fill it to the half way point on the stick, it falls to the minimum mark after around 1000 miles or so, and then remains there almost indefinitely, gradually becoming darker with the impurities, etc. It will fall further, but at my current rate of usage, this is barely noticeable and insignificant.

The car has been serviced twice by my local garage, using the recommended lubricants, in my ownership (12,000 or so miles), and this pattern appears unchanged. I bought it as a trade sale (long story) and it was obvious that it had been neglected a little. It took all of 3 litres to bring the oil up to the full mark before the journey home, although I was later advised that it is better to run these engines around the half full mark. My experience since would suggest that this is so.

I must emphasise that mine is a working car that had obviously not led a particularly easy life. It is also equipped with a tow-bar, but I have no idea if that was for a light camping trailer or a large horse box! The car was very cheap, is both comfortable and now reliable, and owes me not one penny. If you've had yours from new and it has been cossetted all it's life, then their respective conditions may vary greatly.

Regards, John.

[400-ascona]

I have the same issue on the Carlton. After idling for a while there is an oil build up which then quickly burns off when you drive. I suspect one of the turbos which I know has a small amount of compressor damage and therefore believe the bearings/seals will be deteriorating.

I have new turbo cores ready to go in, just not had time to sort it!

[JohnM 855 T5R]

Originally Posted by john.wigley

My car is also an automatic, John, and, yes, the revs do drop to idle on the overrun - but isn't that the same as during your extended wait at the traffic lights?

Regards, John.

Ah, apologies, I didn't know you had an automatic. Logically (and my logic could be faulty), if an auto is on the overrun and the revs are at or just above idle, the engine will still be fuelling which means normal combustion of the fuel should burn off any oil entering the combustion chamber - so no oil puff when reapplying throttle. On a manual, however, the revs will be higher such that the fuel cut-off will be operating. With no fuel in the cylinders the oil won't burn off and so a little will accumulate. As soon as throttle is applied, combustion starts again and the oil burns off giving the puff of smoke.

The provenance of my car by the way is largely unknown though I have lots of service history and past bills. I've only had it 9 months and 1800 out of its 174,500 miles though it's had many thousands spent on it throughout its life and £9,000 in the previous 20,000 miles

Regards
John

[sdg1970]

Mine used to do this quite a bit for the first 12 months when I bought it, but as I gradually got the car tip-top at Stage 0 it rarely, if ever, does it now. I also think these engines are prone to it to some extent and it doesn't neccessarily mean something is shot. I also thought turbo or valve stem seals initially, but after several oil changes over 10k miles it gradually subsided. I do think regular fresh oil, with the odd bottle of seal conditioner additive poured in works wonders.....or it did for me!!

[Cookeh]

This is the most common symptom of knackered stem seals.

[Clogs]

My 1999 T5 will burn oil if topped up to the top level. After oil levels fall to low, they stay there indefinitely, as John Wigley reports. I used to worry about clouds of blue smoke after a long descent... especially in the Alps. I would stop at the bottom of the pass, wait for all passing traffic to go by, and then set off with a huge blue cloud, which cleared quickly.

With low oil levels and no loss of oil pressure, this doesn't happen anymore. The precise cause is unknown.

The oil pressure light never comes on except when the oil level is very low and going round a bend quickly, so it's sloshed to one side of the sump. I keep spare oil in the car, but topping up for a long journey just means it gets burned up and wasted! I just top up with a little and so need only a couple of litres between annual /10,000 mile oil changes.

[Laird Scooby]

Simple answer - abide by the law and switch off after idling for 30 seconds because the delay is going to be longer than that. It'll save you a lot of fuel too.

If you suspect your turbo seals are letting by, chances are that's what the problem is as it all fits - you can buy new turbo cores (as referenced further up by someone with a Lotus Carlton and apparently an Ascona 400) and fit them yourself - much cheaper than having your existing turbo reconditioned.

Not sure if this applies to the 850 as much as the940 but the coolant pipes to the oil cooler and turbo tend to "fur up" after high mileage meaning the turbo runs hotter than it should. This would thin the oil to the point where the vacuum from prolonged idling would pull oil droplets out into the inlet tract and intercooler, opening the throttle would then pull in a cloud of oil vapour that would burn off fairly rapidly with a big blue cloud. If it's the oil seals in the turbo, it will be white, acrid smoke.