WARNING  Compressed air can propel debris into eyes and ears. Keep head away and wear protective eyewear.

NOTE: The illustrations shown will be of the single cylinder air compressor. Differences in procedures for Holset® models SS, QE, ST, and Cummins® air compressors will be illustrated where necessary.

Shut the engine OFF.

Open the drain cock on the wet tank to release air from the system. Close the drain cock after the pressure is released.

Operate the engine to activate the air compressor.

With the air compressor pumping between 550 to 690 kPa [80 to 100 psi], use a solution of soapy water to check for air leaks in the following areas:

• Air compressor cover gasket
• Unloader body o-ring (Holset® only)
• Air compressor head gasket
• Air compressor valve plate gasket (Holset® QE models only)
• Hose and fitting leaks.

If air leaks are found, replace the leaking gasket or o-ring. Refer to the Holset® Air Compressor Master Repair Manual, Bulletin 3666121.

NOTE: Not all air compressors referenced can be used on your engine or application.