Had the turbo pack up on me on the way back from the lakes this weekend in my VW Caddy (1.9 TDi 104). It had been a VERY wet trip up with lots of DEEP puddles. The van was fine on the way up but when I came to leave 36 hours after parking up the turbo failed to spool up. After stopping for a bit it started again and was fine for 30 miles before cutting out again and causing the engine warning light to come on.

Two separate AA patrols said turbo was fine, prob just the boost valve/sensor. Been at the VW main dealer today and they say that the whole turbo unit needs replacing at great cost – something I'm not so sure of.

What are the symptoms of a totally buggered turbo? The van still drives ok with no smoke or anything, it just lacks the boost. One AA guys said that a full-on turbo failure would result in lots of black smoke.

Anyone with a insight?

There's loads of VW specialists around [none main dealers] they're usually very good
Worth trying one for a 2nd opinion

Is it a VNT turbo?

Tubby failure on a D normally results in lots of black smoke, but it depends how smart the engine management is, in this case I would expect black smoke. Tubby failing shouldn't happen intermittently – it's either dead or it's not. If the shaft has snapped you'll get no boost any of the time and probably ditch lots of oil thorough it, and possibly hear lots of unpleasand screeches from it. If the bearing has just failed and removed lots of the turbine blades you might be looking at a silent no-boost situation but its rare for the blades to get shed without such bad bearing failure that it contacts the housing.

My guess is that if its elec-controlled boost it's simply a failure of the valve that regulates the pressure to the actuator. It could simply be that your wastegate has stuck open, massively bypassing the turbo.

What is the engine warning light code (have you had it read?). Dont just jump down the new turbo route without good cause. Where is the turbo on those, is it visible in the engine bay or is it buried down the back?

Even a VNT turbo would produce SOME boost if its mechanisms had failed, but it may cause fluctuation in power.

No idea sorry. It's the PD engine if that makes any difference. 55 plate

Engine warning codes as read from the AA comp were along the lines of 'turbo/supercharger underboost'.

The AA's computers can't read individual sensors on this engine so they couldn't check it out for me.

Thanks for the replies so far.

EDIT: turbo is burried down the back but the first AA bloke 'copped a feel' and said it all felt ok – i guess he meant the fins were intact and/or the bearings were fine.

VNT is variable nozzle turbo, if the VNT control part fails there is a large gap between the vanes & the housing & the turbo can't spool up – a strip down & clean to get the carbon deposits off the mechanism will usually do the trick without a new turbo, see an independant specialist (I would expect a main dealer to try & sell you a new turbo)
Fin or bearing failure would result in white smoke or fins being sucked into the engine 😯

The ECU will go into safe mode if there is under-boost. This can be caused by something as simple as a boost pipe leak or the pressure regulator failing. You may be lucky.

The spectacular sort of Turbo failure is when an oil bearing/seal fails and oil is sprayed into the inlet. The engine then runs on the lubricating oil, can get faster and faster and won't stop until something fails….

The engine then runs on the lubricating oil, can get faster and faster and won't stop until something fails….

Or until you're bright enough to put it in 5th and stall it. I've heard of 2 people writing off engines this way when they could have just stalled it – no engine will overpower its brakes in 5th.

snaps – would have thought you'd still get SOME boost with failed VNT.

http://www.britishvegoil.co.uk/smallengine/vnt.html

It happened to an automatic E-Class and another car on a ramp in a garage.

It happened to an automatic E-Class and another car on a ramp in a garage.

I'll let the automatics off, though only becuse I feel sorry for them 😀

Or until you're bright enough to put it in 5th and stall it. I've heard of 2 people writing off engines this way when they could have just stalled it – no engine will overpower its brakes in 5th.

I've heard similar stories but running on oil mist from crankcase breather. But, not always possible to stop the engine by stalling it as it relys on the clutch not slipping. The engine could be revving well above its normal rev limiter.

Surefire way to stop the engine is to physically block the air intake (wouldn't suggest using a hand!) or discharge a C02 cylinder into the intake.

Cheers for that link coffeeking, very useful info. The only problem is that the error code that that talks about is overboost, whereas I'm getting underboost. Still damn sight cheaper than the £800+fitting+VAT+fat cat main dealer tax that I have been quoted.

alex – give them a call and see what they say, they're obviously more experienced than most of us with that particular hardware so might be a bit more helpful, but with luck it wont cost you a fortune.

The engine could be revving well above its normal rev limiter.

Yup, but it's not necessarily going to be producing more torque than it would when running normally, just more power, and unless you have a catastrophic failure of a seal and start devouring the whole sump full in seconds you're not looking at vast amounts more fuel to burn.

Having stopped a little 1ltr petrol by hand, with the throttle closed, I'd also agree not stopping a throttle-less 2 litre D one by hand! I thought most MOT places kept CO2 fire extinquishers handy for this very purpose – makes sense!

snaps – would have thought you'd still get SOME boost with failed VNT.

No, if the vanes get stuck in the 'base position' then as soon as the engine revs rise the exhaust gases stall the turbo if the vanes don't move.
Good animation at the bottom of this page.
http://www.technologie-entwicklung.de/Gasturbines/VNT15-Turbo/vnt15-turbo.html

Or until you're bright enough to put it in 5th and stall it. I've heard of 2 people writing off engines this way when they could have just stalled it – no engine will overpower its brakes in 5th.

Unless it's a bus engine thats gone, then everyone* runs like **** in the other direction!

*Apart from the nutter who bungs a hosepipe into the air intake and hydrolocks it!!

Yeah, I'll give them a call soon.

My only job at the moment is as a volunteer so I hope there is a cheap fix!

Anyone know what I can do about the main dealer IF there turns out to be a problem that can be solved much cheaper (such as replacing a sensor) that they obviously knew about but are trying to pull the wool over my eyes? But maybe I'm jumping the gun here

I once saw a 16v71 Detroit run away. First start after rebuild, and the control rack stuck open. The noise was horrific (2-stroke diesel) for about 20sec, then with a puff of smoke and a terrible clatter it all came to a stop, after chucking a leg out of bed.
Very amusing, as I had nothing to do with it.

Yes, stuffing a big rag into the inlet is the way to do it.

Anyone know what I can do about the main dealer IF there turns out to be a problem that can be solved much cheaper (such as replacing a sensor) that they obviously knew about but are trying to pull the wool over my eyes? But maybe I'm jumping the gun here

I'd *expect* that of a main dealer.

@snaps – ok, I suppose it depends whether the vanes provide complete turbine stall, I'm just surprised they do that's all.

Yes if the vanes don't move with the increase in revs, you get a little boost at the point where they stick but after that the exhaust gas speed rises & because the vanes aren't moving to direct it on to the vanes at the correct angle, it actually slows the turbo until the gases rush past it.
Have a look at the animation at the bottom of the page in my link above & you'll see.

If its underboost, you may be looking at something as simple as an adrift induction pipe, contaminated (oiled) map sensor or as you say it was wet, if you went through deep water (no one admits it!) may just be a water clogged air filter. but the AA should have checked it. VW also use braided vacume lines to the boost control solenoid and its not uncommon for them to split at the ends and come off. Could also be a buggered turbo though! plenty of cheap stuff to check first though. really could do with someone with a mitivac to check the vacume system.

Well its been at the main dealer all day and I would have thought they would have checked all the obvious things before settling on replacing the turbo – then again, they are a main dealer…

I think somethings got wet (electrical) but i'm not a mechanic.

Get someone to plug it in to a laptop running Vag.com software & ask the same questions on seatcupra.net or other diesl forums.
I've got Vag.com & I'm happy to run it for you but I'm in North Devon.

The code of the AA man's laptop was (i think) P0299 – turbo underboost. Would Vagcom give any more info that that?

EDIT: I'm in West Wilts/East Somerset.

Yes that's saying not enough boost but you know that by driving it – I'd take it to a VW specialist & see what he says.

Will do, found one in Salisbury that I'll potter over to when I get the van back from the MD. Thanks for your advice.