2.5 Allroad, new engine whistle

[bagpipingandy]

Hi some advice required please, its a 2000 2.5TD allroad AKE, 110000 miles, and today I have noticed a new whistling noise under revs. Its hard to describe, it is high pitched & it does mimic the sound like the turbo but it was definately not there before. It is noticeable when revving the engine and on constant revs it can also be heard, I am thinking a turbo problem, or belts or tensioners problem/rubbing.

No fault codes stored with a VCDS scan,

I had the turbo heat shield off and asked the wife to give it a rev whilst I listened under the bonnet, it was really hard to pin point where it was coming from though.

Can a turbo give off an unussual whistling noise if there is a problem? What could I try to prove or disprove the turbo, can I stop it spinning in anyway?

Any one had anything similar or could it be something else?

any advice greatly appreciated,

Andy

[Columbo]

If it's a constant whistle in relation to the rev's i would guess a belt slipping or tensioner bearing squeak.

If the whistle get louder the more boost you have i.e. more pressure then you've got a boost leak somewhere.

With VAGCOM you can run a boost check, but to be honest this will only show the bigger leaks up. The problem with whistle leaks they are caused by small leaks.

A good way to see leaks is to check all the intake connectons for signs of oil being pushed out by the leak. You'll find with most diesels the internal intake route gets quite oily inside.

It's not unheard of for one or both of the intercoolers to leak on these.

[All-rod]

And also have a look if there is much play in the shaft in turbo, by moving it up and down after you've removed intake hose. Your problem more likely to be a leak though.

[nevo]

Almost certain to be a boost leak,dont even attempt to stop the turbo spinning it spins at over 200k rpm,so you can imagine how finely balanced they are.

[bagpipingandy]

Still no solution yet, The whisle/whining noise get higher pitched as you rev it, very difficult to hear it on tickover but clear when reving which would tye in with all your descriptions of a boost leak. ( I hope)

From the PDF attached is this all the possible leak areas you are talking about & I should be checking?Charge air cooler sketch.pdf

I had a look from underneath and could feel/squeeze the 2 large hoses to the cooler but no change in the noise, it is difficult to feel or see the pipe running along the drivers side engine bank but i assume it could be a suspect. does any one know a common leak area?

It is very difficult to visually check the hoses, I have squeezed a few (hoses that is!!) to see if the noise changed whilst running, but fear for my fingers in some bits. What is strange is it is very difficult to trace the noise & where it is actually coming from in the engine bay. I had the lower engine cover off and head up in listening but cannot determine where it is coming from just by listening. I hope it is a leak as I don't fancy putting it in the service position just to find nothing wrong in there, but then I think perhaps I should have a look behind the cambelt cover incase a tensioner is hanging off!! .

thanks for the info so far, I will concentrate on the leak thing again in the morning

Andy

[Peter D]

Use a metre length of screen washer pipe and listen to one end whilst searching with the other. Beware of belts and fans. Regards Peter

[nevo]

I use a bicycle innertube cut opposite end to the valve and rig it up with jubilee clips somewhere near the turbo and other end near the intake then blow it up to test the intercooler, its quiet and you should be able to hear small leaks.

[bagpipingandy]

Well after a lot of searching the engine bay over and under with a pipe in my ear (good tip peter) and all that still no leak found, bit the bullet and put it into the service position tonight, starting it everytime I removed something, to find when I removed the lower belt cover the noise was extremely loud. With the tension off the Aux belt the idle roller showed a bit of movement, a bit of oil in it proved it was the culprit. now removed & car off the road for a few days until I get the part but at least i know what the noise was. I'm glad I checked now!!

thanks for all your replies, it was a whistle noise but slowly developed into a screeching as days went on,

Andy

[Crasher]

I like to replace all those rollers when I do a cam belt but it bumps the cost up.

[adamss24]

Well after a lot of searching the engine bay over and under with a pipe in my ear (good tip peter) and all that still no leak found, bit the bullet and put it into the service position tonight, starting it everytime I removed something, to find when I removed the lower belt cover the noise was extremely loud. With the tension off the Aux belt the idle roller showed a bit of movement, a bit of oil in it proved it was the culprit. now removed & car off the road for a few days until I get the part but at least i know what the noise was. I'm glad I checked now!!

thanks for all your replies, it was a whistle noise but slowly developed into a screeching as days went on,

Andy

If your car is high mileage i would check and replace the metal bushes and the steel spindle of the pivoting arm on the aux. belt tensioner. The bushes are very thin and wear out thus rubbing into the intercooler/pas bracket wich is soft alloy and will require replacing if it goes trough. If you catch it early it might just cost-you a tenner, if you let it rub more the cast bracket is over 100 quid and a real pain to replace (A/C compressor, oil cooler then the bracket needs to come off-messy and tricky job). Eventually the alloy will wear and it will put the belt at an odd angle then it will burn trough the acoustic shield and will jump off stopping the engine or -if you unlucky and the timing belt is weak- it will wrap itself round the crank pulley stripping the teeths off the belt and damaging the engine ! Seen-it before...