Thanks for your quick reply dkveuro. Belt and tensioning system, engine mounts, and A/C compressor are all in good shape. I picked up an automotive stethescope and the noise is definetely coming from the air pump. The ping is loudest on the canister that sits towards the rear of the air pump unit, part no: 104 140 00 81 . The air pump itself is part no: 000 140 26 85. Is there anything I can do here? Or do I need to purchase a new air pump ($$$). Thanks for your help!