Rear air suspension
 

I bought a 2006 Buick Lucerne CXL with the 3800 V-6. I think there is a leak in the rear air suspension. When the vehicle is started the air compressor can be heard operating then it cuts off. While driving there is a continuous cycle of the air compressor cutting on and off. For those with the same experience what has been found to be the main culprit? Also, the racket from the air compressor makes a loud, muffled sound, is that normal for what is to be considered a luxury car? I can imagine a similar thing happening on a Chevrolet Impala if it had a rear air suspension, but not from a Buick. I have looked underneath the rear of the car to find the air compressor, I reckon it to stuffed in the front of the trunk behind the rear seat. What do y'all think?