There are three main statuses when some abnormal noise occurs in the air compressor. 

Here are the reason and solution:

1.There is some abnormal noise in the cylinder:

1)The abnormal objects or the broken valve block. 

Clear them away.

2) The top of the piston and the cap of the cylinder have a crash.

Adjust the gap.

3)The piston ring causes excessive wear and the strike happens in the  groove at work. Change it.

4)There is some water in the cylinder.

2、There is some abnormal noise in the valve:

1)The intake and vent valve group is not impacted.

Tighten the valve and the nut.

2)The valve spring have a failure.

Change it timely.

3)The bolts and the nut loose. Tighten the nut.

4)The gap between the valve block and the bonnet is too great.

Adjust the gap and change the nut if necessary.