Gang,
Did a little compressor maintenance this week (Husky 3 HP, 30 Gal, 10 years old).
I noticed my compressor was making excessive noise and vibrating wildly lately. I decided it was time to look into the situation.
Job 1 was moving all the junk out of the way (bikes, skate boards, trimmers, blowers, shovels, rakes, lumber & metal scraps, cardboard boxes, etc.).
Job 2 was inspecting the compressor (took about 2 seconds to find the problems). I noticed there were 3 bolts laying on the floor, and also noticed 3 of the 4 bolts holding the compressor pump were missing. I removed the safety cage covering the pulleys & drive belt and noticed that several self-tapping screws were missing and that the cage had been rubbing on the pulleys.
Job3 was reinstalling the 3 bolts to secure the pump and aligning the pump pulley with the drive pulley and re-tensioned the drive belt.
Job4 was finding and replacing the screws that secure the safety cage and making sure that nothing was rubbing against the cage. I plugged the power cord back into the electrical outlet and ran the compressor for a few minutes. All nice and quite, no vibration, no rattling, and no rubbing. All is good again.
Jobs 5, 6, & 7. I decided to change the oil in the compressor pump and drain the air tank while I had good access the compressor. The old oil was still clean (a good sign) but fresh oil is always better. The tank had about a gallon of water in it mixed with a small amount of oil (likely from the pump). Last but not least, I replaced the original intake air filter with a new one. I fired up the compressor and ran it until the air tank was full and the auto shutoff switch shut it down. I turned the shutoff switch to the off position and rechecked the tank air gauges 48 hour later... no air loss.
All is well now, it runs quite and the compressor is no longer dancing around on the floor. Time to put the bikes, yard tools, and other junk back into the storage alcove.
An observation: Job 1 took longer than Jobs 2-7 combined. There was an obvious lesson here...