2.5 TDI whistle

[usegoldie]

I have an A6 2.5 TDI (AKN)

When I accelarate hard, I can hear a (subtle) whistle from the engine as the revs climb. As the engine gets to around 3000rpm the whistle stops and I feel a slight pick up in the power / accelaration.

The engine does not smoke at any time.

If it was the turbo hose/s I would expect the problem to get worse with bosst pressure rise, not suddenly go away.

Any ideas?

[bagpipingandy]

I have an A6 2.5 TDI (AKN)

When I accelarate hard, I can hear a (subtle) whistle from the engine as the revs climb. As the engine gets to around 3000rpm the whistle stops and I feel a slight pick up in the power / accelaration.

The engine does not smoke at any time.

If it was the turbo hose/s I would expect the problem to get worse with bosst pressure rise, not suddenly go away.

Any ideas?

I recently also had an engine whistle on my AKN, it turned out to be an idle roller on the Poly v Belt,

read this thread for some fault finding ideas:

https://www.vwaudiforum.co.uk/forum/s...engine+whistle

Andy

[Columbo]

is it an auto?

My auto box makes some whistle type noises most of the time.

[usegoldie]

Just had the belts and rollers replaced, the problem was the same before and after. Having read the thread, I'm pretty convinced that it's a leak somewhere. I'm just surprised that it stops as the revs climb (with the associated increase in power) I would expect it to keep getting worse.

It's not an automatic.

[bagpipingandy]

Just had the belts and rollers replaced, the problem was the same before and after. Having read the thread, I'm pretty convinced that it's a leak somewhere. I'm just surprised that it stops as the revs climb (with the associated increase in power) I would expect it to keep getting worse.

It's not an automatic.

There are a lot of Rollers/bearings and tensioners in there, were they all changed from cam belt, water pump, idle roller & tensioner, to Aux belt which has many and air con ones? A Garage would not change them automatically. it would also have cost a pretty penny to do everything?
The only reason I go back suggesting the rollers, is on mine i could increase the revs and at high revs the noise seemed to dissappear, this could be as it is overcome by engine noise but I could rev through the whistle to make it seem to dissappear.
It could also be a Aircon pump or Alternator bearing.

All the above however would not explain the power increase you say you can feel!!

Andy

[usegoldie]

The cam / aux belt change was carried out by a vw/audi specialist who checked all of the rollers and replaced all of the ones he thought were suspect, and yes - it did cost me a pretty penny!

I will try to have a look at the hoses over the weekend but it would appear that they are pretty inaccessible so I will just have to do my best.

A few posts have mentioned having someone rev the engine whilst trying to find the leak. I was wondering if the turbo spins up properly when the engine is not under load. I was under the impression that the torbo doesn't do much when not in gear and the wastegate stays open??

[bagpipingandy]

The cam / aux belt change was carried out by a vw/audi specialist who checked all of the rollers and replaced all of the ones he thought were suspect, and yes - it did cost me a pretty penny!

I will try to have a look at the hoses over the weekend but it would appear that they are pretty inaccessible so I will just have to do my best.

A few posts have mentioned having someone rev the engine whilst trying to find the leak. I was wondering if the turbo spins up properly when the engine is not under load. I was under the impression that the torbo doesn't do much when not in gear and the wastegate stays open??

The best tip I used was a piece of hose 1m long and use this with your ear over one end to search for leaks in those hard to get areas.

Andy

[carcav]

Hi, check the turbo pipe for a split.