S3 Screeching noise under load

[acmo]

Hi All
I have recently been aware if a screeching noise coming from somewhere when under the slightest bit of load. No noise when revving stood still and only does it after C.5 mins of driving.

I have eliminated that STUPID alternator pulley as I have had the belt off.
Checked boost hoses and small vac pipes

It does sound like a belt squeal rather than a fudged turbo, plus I have not lost any power.
I'm starting to think it may be coming from the Haldex Coupling? I did think it was something to do with the SAI, but the weather is **** here and driving with the window down for any length of time = very wet carpets
Does anyone have any ideas?

[Scott K]

Any chance it's the water pump bearings? You might be coming up for a cambelt change-did the pump get changed last time?

[acmo]

Belt and pump done about 9 months ago, I just can't get my head around why it's only under slight load......if you back off throttle it stops. I may just be kidding myself about the turbo but It spools up as it should.

[zollaf]

sounds like you have a wee boost leak from one of the rubber seals somewhere.

[acmo]

Thanks Zollaf.....it was the 1st thing I looked for but soon dismissed it for some reason. Going to log data on way to work tomorrow morning and see what's revealed

[zollaf]

a small leak like this won't show up as the turbo will make more than enough boost to compensate. you can try soapy water on the joins and watch for bubbles when revved , or apply a bead of grease and go for a drive ad see where the grease is blown off.

[acmo]

It really doesn't sound like a leak.....it's sounding more like something mechanical 😭

[acmo]

Oh dear, I have found it......had it in bits today, checked for boost leaks, end play on turbo, cam belt idlers, Haldex then I spotted it..........A bit of rubber from an engine cover had nestled its self perfectly under the prop coupling from the bevel box thus screeching when engine tilts back under load.
I could not believe it!
Suitably Embarrassed