Our Auxiliary Air Compressor seemed to be getting louder last week. On Friday morning, it got much louder with a distinct "knocking" sound.
A quick check of the compressor on the tray showed the rear two rubber motor mounts had split. I searched for a part number, couldn't find a specific part or source. I looked locally at various shops, nothing. A friend mentioned McMaster-Carr.
Found out these are called vibration-damping sandwich mounts. Looked at McMaster Carr online. Found the exact replacements. These have 5/16-18 threads on the stud and insert, they are 1" in diameter, 1" in depth. The part number I used was 9378K16, arrived the next day from Chicago.
Easy fix... Working great again.
Best, Jeff