Turbo Kickback Or Overboost??

[fasttdi]

I have a A4 TDI 2004. This problem has probably been covered before but as much as ive searched its not had a fixing solution as yet!

Gradual acceleration upto 2000rpm give a sort of kickback maybe an overboost as i can hear a 'metalicy' spinning noise. This only happens upto 2000rpm.
Its getting worse week after week and I dont really know what to do next.
Ive been to the dealers and have had diagnostic equipment attached but no fault codes are stored......

any help would be appreciated... thanks

[wahwenwong]

Hi Mate, I think the turbo shaft bearing may well be on its way out

[fasttdi]

That sounds quite expensive, does that mean i need a new turbo or can this one be repaired/cleaned???

[wahwenwong]

Your old one can surely be repaired but may be costly, check out ebay for a good secondhand unit, a 41000 miler for a passat recently went for £130.

What I think is happening to yours is there may be a lot of up and down play in the shaft bearing, on lower revs the vanes are expanded to shift more air and I think they are just catching the housing........as revs increase the vanes retract slightly and do not touch the casing.......what do you think? does that sound right to your cars symptoms?

it is unusual on a diesel, unless high miles and or not very frequent oil and filter changes, petrol models is more common as the heat is much much higher.

[fasttdi]

What I think is happening to yours is there may be a lot of up and down play in the shaft bearing, on lower revs the vanes are expanded to shift more air and I think they are just catching the housing........as revs increase the vanes retract slightly and do not touch the casing.......what do you think? does that sound right to your cars symptoms?

it is unusual on a diesel, unless high miles and or not very frequent oil and filter changes, petrol models is more common as the heat is much much higher.

i couldnt have described it better myself mate, now that explains the noise but would this sympton also give me a hiccup on accelleration and if i was to keep driving would it cause further damage?

[wahwenwong]

Yes it could give you a hickup on acceleration because as the vanes catch the housing the turbo will suddenly slow down and then you have a reduction in air flow, so less power..........in theory! so then you put your foot down a bit more to compensate and inject a load of diesel.........which = more exhaust gas ........then the turbo gets dragged by the scruff of its neck back up to a speed were the vanes don't catch the housing and you get your power back.

Ive had this happen a few times on the drag strip with petrol driven turbos that have spent most of their life supplying a lot more boost than they were designed for, they begin to smoke (blue) and make a jingle kind of noise for about 10 -15 seconds when you turn the car off. my mates car eventually sheared the turbo shaft in half so he got no boost at all .......just clouds of (white) smoke as the engine oil started to leak into the hot exhaust manifold, we couldn't actually see the dual carriageway behind him (both lanes)!!. we changed the turbo and the car was fine.

Will it damage your car? Not if the vanes stay were they are........bu if lumps break off and make their way into your inlet manifold ........ then yes it could! I have not in my experiences seen a turbo actually get ingested by the engine ........ but its your car = and your call

[Marco34]

wawenfukinwong seems to have it spot on.

Fasttdi. Is it a whistle spinnig noise of definitely metallic? If it's getting worse then it is best replaced. Mine does whistle quite a bit but always has done from 13k miles. I think some vary and have recently read this. There seems to be a splurge of turbos failing at present.

[wahwenwong]

thats a coincidence Marco34, my A4 TDI sport 2001 (51) has always made quite a loud whistling noise spinning up the turbo aswell, especially noticeable with the drivers window is open

The metalic spinning noise that fasttdi has noticed will be similar to this but at the same time noticeably different, almost as if a tiny muffled circular saw were involved!

My car has 110,000 on the clock now and "touch wood" the original turbo seems to be fine, Ive had the revo remap now for at least 40,000 miles of that with no problems at all. i have changed the MAF once and I change the oil and filter at 8,000 intervals, I always use an engine flush and synthetic oil.

[Marco34]

thats a coincidence Marco34, my A4 TDI sport 2001 (51) has always made quite a loud whistling noise spinning up the turbo aswell, especially noticeable with the drivers window is open

The metalic spinning noise that fasttdi has noticed will be similar to this but at the same time noticeably different, almost as if a tiny muffled circular saw were involved!

My car has 110,000 on the clock now and "touch wood" the original turbo seems to be fine, Ive had the revo remap now for at least 40,000 miles of that with no problems at all. i have changed the MAF once and I change the oil and filter at 8,000 intervals, I always use an engine flush and synthetic oil.

Blimey, I'm only 37k. I see what you are saying re Fasttdi's turbo. Not the whistling noise on ours. How have you found the remap then? What BHP/torque is the car running? I've fancied having a remap but been a little put off with stories of clutch and gearbox having a hard time.

I'm with you re oil. That said I drain mine every 5k or 6 months as running to work in Winter, my engine does not get hot. I use Millers Hi-synthetic. Who's brand do you use?

Cheers

Marco

[wahwenwong]

I just use any good synthetic I have to hand at the time, I forgot to say; yes i have had a clutch , But the gearbox seems to be bomb proof. i can't envisage life without the remap though. 295 ft lbs torque and 180 horses is just bliss! Always brings a smile to my face, have you seen this?

http://www.youtube.com/watch?v=9BvjJjL7Z50

Unbelievable