chirp, chirp noise when a/c is on w210
 

So now that my oil leaks are all fixed I am moving onto my chirping noise coming from my a/c compressor/pulley area. It only makes noise when the a/c is on but I am guessing I should replace the belt, roller, tensioner and spring?

Anything I am missing or am I not addressing the problem here?

I take it the sound isn't emanating from the AC clutch.

Can you at least tell if it is coming from left, middle or right hand sides? Have a mechanics stethoscope? Suggest dropping tension on the belt and spinning everything by hand to see if you feel any drag or unevenness in bearings.

I would doubt it is the spring or damper shock. Could be the roller pulley but they usually wobble or are subtly out of alignment with the belt when bad. The pivot tensioner can get dry and squeak or chirp. It has a sacrificial brass(?) sleeve inside it that can get dry and wear.

Alt bearings go bad too.

*edit*
Forgot to mention that you should check the motor mounts too. Collapsed mounts can cause belt problems too. A big rubber bushing between floor jack and oil pan and lifting engine 1/4" (NO more) with AC engaged might tell you if they are part of the problem.

Thanks for the reply-

I do have a stethoscope, although now I am having trouble getting to chirping noise to stay, well, chirping.

Thinking back, the noise increased after I cleaned the engine after fixing the oil leaks. Today it only "chirps" when the A/C is on, and I place the car in gear-and then for only about 5 second bursts. Just enough to drive you crazy..Its definitely coming from the drivers side of the engine. Maybe it is that brass sleeve that is dry and needs some lube.

The previous owner told me the motor mounts had been replaced recently but I do not see any paperwork for those in the stack he gave me, only the belt tensioner shock.

Left side would be the roller, AC and PS pump pulleys. Release tension on the belt and spin the roller and PS by hand and see if they spin freely. The roller has sealed bearings and should be very smooth.

Washing the engine may be the key. Could use a screw driver and try to pack a bit of grease between timing chain cover and the rear of the pivot arm. I've done that on mine before. There is a washer back there so it is impossible to pack it w/o removing it completely. Requires a 17mm hex and some disassembly to remove it. First time took me 90 minutes or more; last time only 18 minutes when the roller pulley snapped off becasue of defective casting.

I packed some grease where you said between the arm and the chain, then put a new belt on and no more noise!

I am sure it was just the belt, I guess I was over thinking it.