The piston rings are worn out.

Overhaul or replace the air compressor.

The engine air filter is dirty (diesel engine).

Replace the engine air filter.

The air compressor air strainer filter is dirty (gasoline engine).

Replace the air compressor air strainer filter. Refer to Air Compressor Air Strainer Filter Replacement .

The inlet vacuum is high.

Clean or repair as needed.

The air compressor oil outlet hose is restricted.

Remove the restriction or replace the air compressor oil outlet hose.

The engine oil pressure is too high.

1. Determine the cause of the condition.
2. Repair or replace as needed.

The air compressor oil inlet hose is flooded with water.

1. Determine the cause of the condition.
2. Repair or replace as needed.

The air compressor oil outlet hose is flooded with water (gasoline engine).

1. Determine the cause of the condition.
2. Repair or replace as needed.

The air compressor oil outlet return passage is flooded with water (diesel engine).

1. Determine the cause of the condition.
2. Repair or replace as needed.

The piston rings are not properly seated.

Overhaul or replace the compressor.

The back pressure exists from the engine crankcase.

Determine the cause of the back pressure and repair.