A4 Turbo screech?

[smithen999]

Hi Gents,

I'm not new to this site, have been a golf owner for the last few years. Got myself an A4 Avant Sline 170 quite recently, its the second one ive had and I must say its not as responsive as the first. One thing ive particularly noticed is that when the turbo starts to boost, I get a horrendous squealing noise (similar to screeching brake pads) which is extremely annoying! Anybody experienced this?

[gblades]

That doesnt sound good. It certainly shouldnt be making that noise and I would get it checked asap.

[s-express]

sounds like a boost leak to me. Need to get the pressurised side filled with compressed air and listen for leaks. easy peasy.

[smithen999]

Thanks for the replies guys, I havent done a pressure test on the hoses as i'm not convinced its a boost leak as there seems to be certain conditions that it doesnt happen; when the dpf is regenerating (seems to have more power when regen) and when ive been using it after long runs. I read a thread over on the T5 forum and somebody had a similar issue which turned out to be the turbo to exhaust manifold joint leaking. Ive had a look but I cant see any evident soot marks so at a bit of a loss. When I had it serviced recently at an Audi specialist I asked them to have a look - they reckon its fairly normal??! I know it isnt as I used have an identical model! Just wondered really if anyone else had suffered a similar complaint.

[smithen999]

UPDATE!

Changed the EGR changeover flap on the egr cooler as there were a few soot marks underneath, and a smell of exhaust fumes aparent in that area - Problem solved! Part No is 03G 198 512 'repair set' I think Audi charge around £60 but there is a chap on ebay selling brand new genuines for £40. It actually seems alot more responsive lower down in the revs now as well as higher up (and no screech). I know there are a few threads about low down power issues so it may well be worth checking this as it probably often gets overlooked. Hope this will help somebody in the future.

[patrickhorton]

Thanks for doing this thread, Smithen. I have something very similar. Had a turbo recon in June to try fixing this intermittent noise problem. Until last week it seemed to have worked. .... Now it's back! Absolutely gutted as the turbo job took a lot of graft I wouldn't want to repeat.
Will take a look at the cooler flap now.
Patrick

[utensil999]

Hi Patrick,

I also had a leaky cooler flap, and it was leaking exhaust fumes and soot all over the top of the turbo and there was a big black layer of soot on the underside of the bonnet over that area also. I was getting a strange screeching noise also but this did not cure it.
IMG_6133sml.jpg

i then found this article which seems to be exactly what my BRD turbo does, it might be completely irrelivant to you but if you have a BRD engine this link might be of interest,

Question Noise when coming off throttle

cheers

matt

[patrickhorton]

Smithen - I Reckon I owe you a beer. Looked into the cooler flap thing and mine is working fine but it put me onto something crucial. There is a really thin metal gasket under the flap housing. There's a lot of stuff on the web about noisy gaskets on turbo pipework. Mine showed some soot marks from leaking - also on egr take-off port from turbo. Made some gaskets from some high temp material off ebay and bingo - noise has gone (for now) . It all makes sense - the gasket buzzes in resonance with the turbine wheel as it leaks - a bit like a mouthorgan reed. After a while it used to go quiet (from sooting up I guess) then after a DPF regen with 800degC exhaust temps it used to start again (presumably because the soot was burnt off. The EGR cooler has been off a couple of times before the noise started and i didn't replace the gaskets at the time.
Thanks again.
Patrick

[patrickhorton]

Hi Patrick,

I also had a leaky cooler flap, and it was leaking exhaust fumes and soot all over the top of the turbo and there was a big black layer of soot on the underside of the bonnet over that area also. I was getting a strange screeching noise also but this did not cure it.


i then found this article which seems to be exactly what my BRD turbo does, it might be completely irrelivant to you but if you have a BRD engine this link might be of interest,

Question Noise when coming off throttle

cheers

matt

thanks for the links. Hope you get your noise sorted. If you have the screech aswell, you might want to replace the gasket where the turbo joins the egr pipe. It is only a couple of pounds and ten minute job to fit.
Patrick

[utensil999]

cheers for the update Patrick ill take a look at that

matt