really annoying knocking rumble noise

[mar1b0ro]

just posting to see if anyone else has had similar problems with an annoying sort of knocking grumbley noise that i am currently experiencing coming from the (seems like) front right underside of my S3. I have recently had the turbo fully rebuilt on the car and it seems to be running absolutley fine, and the knocking noise only happens when im coasting or easing off and seems to be worse when turning left and/or going downhill. Its a hard noise to describe but its fairly loud and i would imagine could be heard from outside of the car and sounds like a metal on metal noise and only happens when the car is in gear. Its worse when the car is in second or third and just coasting along without my foot really being on the accelerator. As soon as i gas it, it dissapears and the engine sounds fine. When its happening and i put the car into neutral, it dissapears..could it be something knocking on the driveshaft? any suggestions would be gratefully recieved...its starting to p**s me off.

 

[beachbuggy]

Check the pipe work that comes off the turbo, especially the water inlet pipe. If it's not been put on quite right then it could be knocking on the engine or intercooler pipe work. As the engine revs or the car turns, the engine will twist on it's mountings and could then knock if something is misaligned. If it's only started to happen since the turbo was rebuilt then I would start there as the likely cause.

 

[mar1b0ro]

cheers for the suggestion, yeah its only started doing it since the turbo has been rebuilt so i guess thats probably the best place to start. The thing is though im sure its only really knocking when the turbo isnt operating. If it was something with the turbo, wouldnt it be knocking more when it was boosting?