Turbo squeel

How do you know it's coming from the turbo? I ask because I've never heard of "turbo squeal" before. Is it the same with the lights on full beam or turned off?

It normally happens when the thrust bearing in the turbo is worn, and happens just before the turbo smashes the compressor wheel on the housing. I'd suggest getting it rebuilt ASAFP before the repair beomes even more expensive.

Is it the turbo itself, or the wastegate mecahnism - my Tdi makes lots of whistling noises as the excess pressure is vented.

Having said that, probably better to get a professional opiniion sooner rather than later. Regards Graham Carter

ON that topic, what it your switching off proceedure. I have a 300tdi and I try to religeously run it for at least a few seconds (10-20) if I have just puttered into a parking, but if I have been going some and don't have much slow down room, like coming off a freeway into a garage, then I usually let it run for a good minute or so.

I know most salespeople when selling a turbodiesel will tell you that running your turbo down is old school and you don't need to do that on a modern car. I think that is a load of kak.

In South Africa turbo diesels have only recently become popular - in the last five to seven years I would say - and so a lot of people that are used to thrashing their 3 series beemer or whatever, are now buying diesel wagons.

Because of our somewhat unique propensity for speedy and agressive driving and high altitude, the turbos work very hard and are then immediately shut down. I know the 320d bmw blows more turbos here then just about anything else, any vehicle with a turbo seems to come in for a fair bit of stick.

What are the opionions of the group?

Regards Stephen

That's what happened to a turbo in one of my cars, no squeal though, just a horrible grating sound and no power as a vane came off after the impact! If the OP's turbo is rubbing its bearings and has been for a while, that's quite surprising.

I don't bother to idle the engine any more as the reasons for idling the engine really only apply if you are revving it under load, or running it so hard that it glows red. Driving normally and the usual parking of the car gives the turbo easily enough time to stop spinning, and I've never seen my landy get so hot for me to worry about the oil-baking problem. There are cars that I would worry more, but my landy and my audi 1.9TDi aren't among them. Some cars (e.g. my audi) now claim to have a thermionic oil circulating system that stops oil sitting in the turbo to bake. I'd regard sitting there for a minute with the engine running as completely excessive.

The squeal isn't actually anything rubbing - it's the air being forced thru the tiny gap between wheel & housing.

Coming off a freeway shouldn't be an issue - as the engine's not doing a lot of work on level ground (even at speed) so EGT and turbo temperature should be reasonable - enough idling to let the turbo slow is probably all that's necessary, say 10-15 secs.

Conversely if you've been working it hard (eg towing uphill) a cooling period of a minute or so will be beneficial.

That said, modern turbochargers with water cooled bearing housings are much less prone to failure from excessive heat anyway, so the problem is far less severe than with older vehicles.

When you say "wheel and housing" do you mean the turbo vanes and the turbo housing, and if so why doesn't that happen to a non-fubarred turbo? Just trying to get my head around where the air is going here, mostly for my own curiosity.

There's a huge yellow label on the dash of Pinzgauler's (sp?) - "Allow to idle for 2 mins before turning off" (or words to that effect).

A new concept in warfare!

Getting back on topic - my 200Tdi has had turbo wine for about

Richard (Waiting for the bang)

Hehe, I wonder if that's the older ones with the air-cooled petrol engines or the newer ones with the Golf diesel engine in it. I'd have thought that the Golf diesel would be modern enough to not need idling, and the air-cooled engine might need the fan for a bit longer to bring the temp down.

I wonder what turbo whine sounds like, given that they whine anyway as part of normal operation. Obviously describing it in a newsgroup isn't really possible....

Hmmm... Pinzgauer's we had were not Golf engined, but they were a vw sourced

My bmw 330d had a bit of whine from the turbo occasionally, mainly in cold weather so I suspected some sort of resonance issue based on air density change. Was never loud enough to bother me and it always went fine, so ignored it! Badger.

fanie came up with the following;:

I'd agree to some extent, but not to the degree that you do.

If I've been towing the caravan or horse box (every weekend virtually all year round) then I let it idle for a while, but don't really time it, just while I gather my house keys, wallet, phone, sat-nav etc etc and get the kids out. If I've been driving solo round town or poottling about I don't worry about it at all.

On or around Thu, 26 Jan 2006 08:22:12 +0200, fanie enlightened us thusly:

I'm inclined to agree - but I reckon a minute is probably overcooking it. driving up at high revs and turning off leaves the turbo still spinning and the pressure oil feed not working any more, which is the argument against it. But I doubt the turbo spins at high speed for more than 10 seconds or so after coming back to idle, if that.

Ages ago, Commer made some 2-stroke diesel engines (and Foden, I think, but the comment pertains to the Commer) for lorries. In those days lorry engines were such as the 5LW Gardner and the AEC 690 which were flat out at about 2500 revs and normally pulled about 1800 or less, and had huge capacity cooling systems to cope with an engine that wasn't prone to overheat.

The Commer was much faster running and hotter than the typical engine of the day and quite a number got broken 'cos people were getting it hot running at at speed and then pulling up and switching off. The coolant then stopped circulating and uneven colling warped or cracked the heads. If left to idle for a few minutes to cool down, they were fine.

hens-teeth territory now. I did see a (preserved) 2-stroke Foden on the road a year or so ago, makes a marvellous noise, but not in the same class as a "Deltic".

If you google, theres a very anoraky site with recorded train noises including Deltics.

On or around Thu, 26 Jan 2006 09:00:10 +0000 (UTC), beamendsltd enlightened us thusly:

that may be more about engine cooling than turbos, though

Once, when I were an anoraky trainspotter, I was standing at Paddington station watching an intercity 125 (AKA HST), which runs a Paxman Valentia V12 turbo diesel, depart. So were some other simialr types.

Due to the nature of the transmission, as it pulls off it revs up to fairly high revs, and this particular one produced a scream from its turbo which must've been audible at least all over the station, and probably for about half a mile around. Still seemed to be running though. Sundry comments were made about how long for.

some turbos are just noisy... Although the sudden appearance of noise or a sudden increase needs looking at.

Not wanting to contradict any other posts but if it more of a whistle while under load then it could be something as simple as a very slight air leak from an inlet hose either side of the turbo or intercooler.

Huw

I would agree with that and add that the water is pumped electrically through the turbo on modern BMW [and other] engines for quite a while after shut-down. The main danger these days is from stalling a hard worked engine or shutting down straight away before the turbo has spinned down [those 10 seconds of idleing are vital in some circumstances] because once the engine is killed no oil is forced through those bearings. Restart a stalled hot engine with no delay.

Huw

Yep - compressor wheel vanes and the housing. As the thrust bearing wears the shaft can move axially which changes the clearance. The change in clearance changes the pitch of the sound - not unlike changing the note when whistling with your mouth.

IME turbos that have shown a marked increase in noise are normally ready to do themselves a mischief. It's not too hard to use a DTI to check the end float of the shaft if you're concerned about it either.