Unusual Whistle/squeal

[seatkid]

Disturbing event this morning. Slowing down on slip road after 20 miles at 70 mph and I suddenly hear a constant high pitched whistle/squeal. Think its just one the lorrys in front brakes. But no, the lorrys depart but I can still hear the constant whistle/squeal. As I pull round the roundabout and start looking for a lay-by, the squeal subsides slowly (in volume but not pitch) but starts up again in a minute or so, albeit quieter. I pull up and pop the bonnet and try to see if I can see where its coming from.

 

Unable to determine location exactly, just generally to left of engine and maybe towards back. Anyway the noise gradually subsides again and doesnt come back.

 

First thoughts were -

 

1. cambelt tensioner or roller - these have been changed recently - although the garage didnt return the roller so I'm not 100% sure they changed it (VW garage using official kit)

 

2. Leak from a/c - maybe low side connector - it was refilled yesterday - the a/c wasnt on at the time and it still works without any indication of lost gas (noise)

 

3. Auxillary item - tensioner, alternator or power steering pump

 

4. Turbo?

 

4. EGR valve, cutting in after prolonged "high speed" run.

 

The thing that puzzles me though is the whistle was fixed in pitch/volume and didnt alter with engine revs, turned a/c on didnt make any difference, hopefully ruling possibilties 1 to 4 out.

 

So, could the EGR valve whistle?

[Neils TDi again]

First you have two number 4s :>

 

Anyway the EGR could indeed be the cause of the problem slowing down from high speed is likely to have caused the valve to open on overun of the engine if as I have now come to belive the EGR is like many other diesel EGR it will be very clogged with exhaust carbons. I have come to understand this after having several problems with the EGR ona 320D BMW and effectively its the same valve on the Galaxy and also just for info it suffers the same problem as the Gal with the MAF. Although the BMW forums recommend cleaning the MAF !

 

Anyway back top your squeal it is likely that the EGR being dirty is slow to close after opening at overun temperatures it should close once it cools down but if thisis the case it will stick again, might be worth getting at it and either cleaning it or replacing it.

 

Best of luck if you do can we get a blow by blow account so I know what to do when it comes to mine ?

[insider]

Would VAG-COM indicate a malfunctioning EGR valve?

[Neils TDi again]

It would register a pressure change but I dont think it would identify the valve as it has only a vacuum operation and no sensor in it.