To rebuild the air compressor it is a very expensive job because it has many parts. I would recommend that you perhaps purchase one at your local junk yard.
Honestly for a problem such as this i would refer you to a mechanic. It could be a number of serious or minor problems. I would recommend you visit your local mechanic.
Rebuilding the air compressor is usually a tedious and arduous task that is negligible to the savings. The parts are not readily available and a new one is not expensive.
