Recently I replaced the pipe from the airbox to the turbo elbow (pictured below) as the flexible part had been crushed but I now get a whistling noise when the engine revs.

 

I've checked all the joins from the ducting in the front grill to the turbow elbow and all seems ok. I suspected that maybe it was the PCV hose that runs from the back of the airbox to the valve in the cam cover but can't really pinpoint where it's coming from.

 

It sounds as though it's coming from the middle of the pipe near to where the 3 chambers come out of the side but on the right hand side, however it's solid plastic with no joins. I tried manipulating the pipe while having someone rev the engine and there was no change.

 

The noise is a short sharp whistle that's only present if you rev from idle and stops within a second and doesn't happen again unless you let the engine drop back to idle and do it again.

 

Any ideas as its got me stumped?

Video of the noise

 

Edited 18 June, 20223 yr by Bepis
Video format not supported

I seem to remember that early cars had a whistle issue and they got it revised part. Maybe that is just a false memory / dream. Search it. 

I'll have a look but the pipe was bought new from Skoda and couldn't find any notes of revised parts.

 

I put the old pipe back on and the noise still persists. The noise may have been there before as with the bonnet shut and inside the car you really can't hear it.

 

However, it wasn't there 6 months ago when I was investigating another noise.

Have you fitted new green O-ring seals to every joint that has that type of O-ring in it - VW Group states that any/all these green O-ring seals must be replaced before re-assembly?

 

The function of these 3 tubes is to act to reduce resonances in the induction tract at that point.

 

Edit:- it would be useful if you stated what happened to cause that area of induction piping to get crushed - as when that happened, maybe something else got damaged, so knowing that might reduce any wild guessing.

Edited 18 June, 20223 yr by rum4mo

I purposely didn't remove any pipes that have o rings so they didn't need changing . I believe it's just the turbo elbow that I've touched but didn't remove which has an o ring seal.

 

Could it be possible I've slightly tweaked it? Needed hardly any force to get the pipe back on to the turbo elbow.

 

Only pipes I removed were those that would need removing or unclipping to change the air filter. Only difference is that I removed the pipe with 3 chambers rather than just moving it aside.

 

I'm going to double check the seal on the air filter box itself as with it being a short sharp whistle I'd assume there's a tiny gap somewhere or something that isn't applying the force necessary on a seal to seal properly.

Re checked the inlet pipe and airbox and both are seated properly.

 

Only thing I can think of that's causing the noise is the turbo elbow has come unseated just enough to allow air to be sucked in from around the o ring that seals it and once the turbo produces enough vacuum in the intake it sucks the elbow in and seals.

 

But I'm not 100% sure as there are 2 screws that hold it to the turbo inlet.

 

Looks like a 20 minute job changing one pipe is now a visit to the mechanic 🙁