ISC, ISCe, QSC8.3, ISL, ISLe3, ISLe4 and QSL9 Engines – Air Compressor Cycles Frequently

Symptom Tree  t005

This is symptom tree t005
Cause Correction

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 the OEM service manual. For applications fitted with selective catalytic reduction exhaust systems, check the air supply line to the dosing control unit.


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 the OEM service manual.


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.


E-type system is not plumbed correctly

Install an Econ valve, a check valve, and system hoses. Refer to the OEM service manual.


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. Refer to Procedure 010-033.


Air compressor pumping time is excessive

Replace the desiccant cartridge on the Turbo/CR 2000 air dryer. Refer to the OEM service manual. Check the air compressor duty cycle. Install a larger air compressor, if necessary. Refer to the OEM service manual.


Air dryer outlet check valve is sticking

Lubricate or replace the air dryer outlet check valve assembly. Refer to the manufacturer’s instructions.

Last Modified:  06-Oct-2006