Audi A3 Knocking/Vibrating - Engine!

[FelixCatFace]

Ok... Need some serious help - The other day i started my car up and could hear kinda like a squeaking belt from the engine, so opened the bonnet to hear nothing. Then to check, i just revved the engine a bit from the engine bay, but when i let off the throttle i could hear a kind of vibrating/knocking this was in time with the engine (sounded a bit like if you have a sander turned on and touch the handle gently on a solid piece of wood) then when the revs dropped a bit it stopped but did it again and again each time i revved it... after it had warmed up after a short drive to the mechanic - there was no sound at all but later when it had cooled i started it up and checked... and sure enough... there it is again.

I'm not sure if it's the turbo buggered or something far worse - cam etc! It's difficult to figure out where the noise is coming from. It kinda sounds like it's to the right of the engine but also sounds like it's down the back of it. Have been told that it doesn't sound like the bottom end.

Any ideas? Cheers!

[350zwelgje]

Hopefully your cambelt hasn't slipped. Know that it is nearly impossible, but a long time ago happened once to me (not VW/Audi - was Japanese stuff) and wrecked the engine. First you still could drive, but engine temperature fluctuated, power loss until the engine gave up and head gasket had blown as well.Root cause analysis showed slipping of cambelt. So the question would be, when was the belt changed, and if it was recent it should not be an issue. If not, have the timing checked/belt changed etc. before other things go wrong.

Rob

[GreenV8S]

What sort of engine is it, how old, when was it last serviced? Hard to diagnose funny noises over the internet but a misfire could produce symptoms like the ones you're describing. If so, and if it's a petrol engine, it may be as simple as the plugs overdue for replacement, or an HT lead shorting on something.

[H2DaE]

Sounds similar to what has happened to my Punto JTD engine, have stripped it and couldn't find anything obviously wrong but it was getting slowly worse so it was probably a slipped belt. I have just decided to change the engine as I got a lower mileage one from ebay for £300...

[GreenV8S]

Cambelt problems are unlikely to be intermittent though.

[H2DaE]

mine wasn't intermittant lol, it was really rough and when you turned the engine off there was this nasty loud metallic tapping noise. but now i've stripped it down there does't appear to be anything wrong.

anyway sorry for the hijack

[FelixCatFace]

Hey guys! Thank you for all your help and suggestions... Just though I'd let you know the mechanic "thinks" it's the turbo but can't be 100%... so I've traded it in for a WRX Impreza! Woo!

Thanks again people!

[H2DaE]

rofl nice one