Holset Air Compressors – Air Compressor Air Pressure Rises Slowly

Symptom Tree  t004

This is symptom tree t004
Cause Correction

Air intake system restriction to air compressor is excessive

Replace the air compressor air cleaner (if installed). Check the air intake piping. Check engine air intake restriction if the air compressor inlet is plumbed to the vehicle or equipment intake system. Refer to the OEM service manual.


Air system leaks

Block the vehicle wheels and check the air system for leaks with spring brakes applied and released. Check for leaks from the air compressor gaskets and the air system hoses, fittings, tanks, and valves. Refer to Procedure 012-019.


Air governor is malfunctioning or not set correctly

Check the air governor for correct operation. Make sure the air governor is located less than 0.6 m [2 ft] from the air compressor. Refer to Procedure 012-017 or 012-018.


Carbon buildup is excessive in the air discharge line, check valve, or cylinder head

Check for carbon buildup. Replace the air compressor discharge line, if necessary. Check the turbocharger for oil leaks. Check the intake tube for oil. Refer to the OEM service manual.


E-type system is not plumbed correctly

Install an Econ valve, a check valve, and system hoses. Refer to Procedure 210-001.


Air system component is malfunctioning

Check the operation of check valves, alcohol evaporators, air dryers, and other OEM-installed air system components. Refer to the manufacturer’s instructions.


Unloader valve is malfunctioning

Check the unloader valve and unloader body seal. Refer to Procedure 012-101, 012-103, 012-104, or 012-106.

Last Modified:  13-Jun-2005