Hello,
I've been reading a lot of information on turbo failures on cars like BMW 320D models.
Just wondering is there any maintenance that needs to be carried out on turbos besides the normal oil, oil filter & fuel & air filter change.
My passat has 170,000 miles on the clock and I'd like it to stay climbing gracefully without problems ;-)
Thank you,
Carlover
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Shortening the time/mileage between oil changes would be useful on an engine with that many miles.
Also check out:
www.honestjohn.co.uk/faq/faq.htm?id=68
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Thanks NeilS,
Will do. Fingers crossed!
Carlover
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I must admit that I've never really understood why a diesel engine turbo needs the wasteful idling cooling down treatment. Diesels have no intake air flow control like petrol engines; the amount of air processed by the engine is governed only by the speed on the engine and the turbo boost.
My thinking goes as follows, you are barrelling down the M6 with your diesel engine at 3000 rpm and suddenly you decide to stop for a coffee. You take your foot off the accelerator, at this point the engine has no fuel going into it, but the engine is still spinning at 3000 rpm so it has the same amount of air going through it, but the exhaust temperature will be a lot cooler. As there is lots of cool air going through the turbo, it should mean that the turbo cools down quite quickly in the rundown.
Petrol engines are different in this respect in that the air flow immediately reduces when you take your foot off the accelerator so you would not get this cooling effect to the same degree.
Anyhow, I do wonder if this idling of a diesel turbo after a long run thing is a bit of an old wives tale. I am sure someone knows more than I do and I would love to hear what they think. I do feel it is frequent oil changes and good quality oil that is the key, not this idling thing.
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You sound convincing Canuck, but a friend has a V6 diesel LR Discovery that lunched its turbo at 8000 miles, and he too, although a sometimes very fast driver (owned a whole string of 911s during his advertising career), dismissed the idea of simmering the turbo down as a load of cobblers.
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I think it depends a lot on the vehicle and the way you drive. I have been driving Citroen turbo diesels for about 20 years and 500,000 miles and I have never had a turbo fail.
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A friend of mine had an Escort RS Turbo "back in the day" which got 175,000 miles out of the original turbo and that was when turbos were accepted to last 100,000 miles tops. The car was serviced to Ford's schedule, driven hard, and received no special treatment, but the roads to his estate are narrow, residential streets with traffic calming and multiple tiny roundabouts. There was a good 5 minutes of this before shutting down in the evening and before opening it up in the mornings. We reckon this gave the turbo a natural warm-up and cool down period.
This turbo was actually rebuilt by a local specialist and refitted to the car. It did another 10k before the car was written off in a smash.
I sometimes wonder when my S60 will spring turbo failure on me (128k and still original), but at the moment it's still doing the job. My father-in-law sold a 200,000 mile mk3 Golf TDI a couple of years back, which was still on its original too. I think modern oils have greatly improved turbo life.
On the Scenic, I change the oil at midpoint between the ludicrous 18k service intervals. Even my local dealer reckons 18k is too long on the same oil for any turbocharged engine. For the cost and minimal hassle, it's a no-brainer for me.
ISTRC reading that diesel engines give turbos an easier time than petrols anyway, because diesel exhaust gases are cooler. Not sure how true this is.
Cheers
DP
Edited by DP on 16/05/2008 at 10:38
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DP is right, turbo's are much less stressed on a diesel. The exhaust gas temperature is much lower that a petrol engine, due partly to the combustion efficiency and also the fact that there is no throttle in the air supply, so you have a continious full flow af air through it - when did you last see a red hot turbo on a diesel?
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Red hot turbine housings are commonplace on commercial diesels running at or near full output. A diesel turbocharger will generally outlast an equivalent unit fitted to a petrol engine because the part-load conditions are more favourable - the diesel has no throttle and hence runs on excess air under these conditions. Average exhaust gas temperatures are therefore lower.
Synthetic based oils have contributed a good deal to turbocharger reliability as have improved materials within the units themselves. As far as prolonging their life goes, I would agree with frequent oil changes to the recommended specification - the interval depends on the usage regimen - and I would very definitely advise a cool down period after running at or near full output.
It's soak-back heat from the turbine to the turbocharger bearing in the absence of a cooling oil flow which does the damage as the remaining oil film will break down on the running surfaces of the bearing and form ash or varnish. A cool off period similarly benefits the engine as well as the turbocharger.
659.
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My ancient (1995) 405 td still pulls very strongly after 121k. Most of my mileage is mway and I always idle before switch off. I dont claim to understand the technical side of this but it may well have helped the turbo last. I always change the oil every 5k without fail.
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