Redbullf189

So I just got done dumping $2700 in my 2002 s4, replacing the timing belt, thermostat, water pump, control arms, fan and bushings, n Ive only owned it a week. Now, coming home, when it idles, it sounds like a damn diesel engine. I looked and everything looked normal, and my mechanic said it could be something with a pulley? Any ideas?

ezveedub

Is it only at idle? Does it have a rattling sound from one of the cylinder heads? The cam tensioner can make that noise from one of the heads if its going. Low oil pressure will make is sound like a mechanical sewing machine. If you remove the serpentine belt and it stops making noise, then an accessory driven by the belt is the cause of the noise.

Redbullf189

Well the cam tensioner was replaced as well so I doubt thats it. I actually think the fan they installed might be out of allignment because it sounds like its coming from there. The sound speeds up when I accelerate.

Peter Badore

The shop may have damaged the fan clutch using improvised methods to remove the left hand drive threads on the fan clutch attaching nut. I have seen some shops use a pneumatic impact bit to remove the left hand threads on the fan clutch--very crude to say the least. Also were the intake camshaft timing adjuster chain pads replaced? A broken or missing chain adjuster pad can make a lot of noise at idle. Usually it is the bank 1 (right side cylinder head) chain pad that has problems first.

Brewhaha

Usually my engine will get noticeably louder over 3500 miles.

Small Town Terrorist

Timing belt roller tensioner. When it fails, the timing belt is loose making a diesel sound. You may get a code on the camshafts because of the loose belt.