My wife’s 1990 XJ-S convertible (5.3 L V12) recently started making an irregular mechanical chattering sound at the right front of the engine. The sound could clearly be heard with the hood (bonnet) closed but was much louder with the hood open. I did a side by side comparison with my 1990 V12 Vanden Plas (5.3L V12) with both engines running using my mechanics stethoscope and I localized the noise to the Air Pump (EAC8839) which very loud on the XJ-S and barely audible above normal engine noise on my V12 Vanden Plas. I removed the Air Pump from the XJ-S and confirmed that it was the culprit when I turned the pulley by hand and heard the same unmistakable mechanical chattering noise. I was anxious to get the car back on the road quickly and delighted to find that my local O’Reilly’s auto parts store could order a rebuilt one and get it on hand for me that afternoon. The replacement Air Pump I purchased was a rebuilt Cardone 32-293 for about $100 US. It was an exact replacement for the one in the car. Originally I thought that I could use one of the spare Air Pumps (EAC3645) that I removed from my XJ6 parts cars but when I compared them side by side I discovered that although they were similar they used a different diameter pulley and smaller pulley bolts. I swapped over the pulley, pulley bolts, outlet adapter (using the new gasket provided with the rebuilt Air Pump) and mount bolts from the original Air Pump to the replacemement one and easily installed the replacement Air Pump. When I started up the car late last night the mechanical chattering noise was gone. On a short drive today I confirmed that the engine has returned to it’s nice smooth sound again and the chattering noise is gone.
The attached pictures show the old Air Pump before the removal and replacement, the box of the rebuilt replacement Air Pump, and the replacement Air Pump in place.
I live in California, USA and this car is subject to visual and gas analysis Smog Tests every two years. So a proper replacement was required in order to pass the upcoming CA Smog Test.