Grinding Noise After Starting

[jmusser218]

I'm sorry if there's already a thread on this, but I haven't been able to find one anywhere. Every time I start my car, there is a loud grinding sound about 15-20 seconds after I do so. The noise seems to be coming from the trunk and lasts for about 5 seconds. It started happening after I replaced the fuel filter in my car, however I don't know why that would cause the noise. I believe it is the air compressor for the rear shocks because when my car is idling on an uneven surface, the grinding noise comes on and lasts for 30 seconds to a minute at a time and happens constantly, as if it is trying desperately to fill the shocks with air. I can't find anything on the location or replacement process of the air compressor, and I can't find anything but aftermarket air leveling systems for the car. Any information would be very helpful. I plan on replacing the rear shocks with the Monroe's as soon as I get the money. Thanks everyone!