ISC, ISCe, QSC8.3, ISL, ISLe3, ISLe4 and QSL9 Engines – 012-007   Air Compressor Cylinder Head, Single Cylinder

WARNING  Batteries can emit explosive gases. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To reduce the possibility of arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.

WARNING  Do not remove the pressure cap from a hot engine. Wait until the coolant temperature is below 50°C [120°F] before removing the pressure cap. Heated coolant spray or steam can cause personal injury.

WARNING  Coolant is toxic. Keep away from children and pets. If not reused, dispose of in accordance with local environmental regulations.

WARNING  Air pressure must be released from the system before removing the air governor. The governor can be under pressure and cause personal injury.

• Disconnect the batteries. Refer to Procedure 013-009 in Section 13.
• Drain the coolant. Refer to Procedure 008-018 in Section 8.
• Remove the air governor or air governor signal line, if necessary. Refer to the OEM service manual.
• Remove the air compressor coolant lines. Refer to Procedure 012-004 in Section 12.

Remove the four 8-mm capscrews.

Do not remove the three M6 internal hex capscrews at this time.

Remove the head and gasket.

NOTE: Due to an interference with the fuel pump on some applications, it can be difficult to remove all four mounting capscrews completely from the air compressor cylinder head while the air compressor is still mounted to the engine. To remove the cylinder head, completely remove the front two capscrews and completely loosen the rear two capscrews. Simultaneously lift the left rear capscrew and cylinder head to unseat the locating dowel from the air compressor housing. Slowly rotate the head counterclockwise, using the right rear locating dowel as a pivot point until enough clearance is available to lift the cylinder head off of the air compressor.

Inspect the cylinder head for signs of an external coolant leak. A large coolant leak from the air compressor cylinder head will have blistered/removed paint and/or have a white deposit build up.

If a large coolant leak is observed, the head should be rebuilt with a gasket kit. Refer to the Cylinder Head Gasket Kit in the Install section.

Inspect the unloader valve plate and cylinder head for deep scratching or scoring. If the cylinder head is scratched or scored deeply, it must be replaced.

Verify that the unloader piston is in the proper orientation and operates properly. If, upon inspection, the unloader piston and plate are stuck open, exposing any area of the relief chamber, carefully remove the unloader plate from the unloader piston pinions.

NOTE: The unloader piston and plate must always default to the fully closed position.

Place a few drops of automatic transmission fluid into the unloader piston bore. Coat the front and back side of the piston with fluid.

Use a stiff wooden handle to apply pressure to the unloader valve against the spring. Slide the unloader piston through the full range of rearward travel. When the spring is fully compressed, quickly let the pressure off, allowing the spring to drive the piston back to its closed state. Repeat cycling the unloader piston in this manner 5 to 10 times.

If the unloader piston continues to demonstrate any resistance to movement, or slow response while returning to the default closed position, the cylinder head must be replaced.

Inspect the unloader channel and governor supply port, as well as the unloader piston, for signs of rust.

NOTE: Rust present in the unloader channel and/or governor feed port indicates that either the air dryer has malfunctioned, or improper draining of the vehicle air tanks. Use the following procedure to check the air governor for proper operation. Refer to Procedure 012-016 in Section 12. Refer to the OEM service manual for troubleshooting the air dryer, as well as proper maintenance intervals for the vehicle compressed air tanks.

Inspect the intake and discharge ports for heavy carbon buildup. Use the following procedure for proper reuse guidelines. Refer to Procedure 012-003 in Section 12.

While the air compressor cylinder head is removed, inspect the rotating components and the cylinder bore of the air compressor for damage. Refer to Procedure 012-014 in Section 12.

Air compressor cylinder heads can be rebuilt with new gaskets if air or coolant leaks are detected.

Disassemble the cylinder head by removing the five internal hex capscrews.

Separate the cylinder head.

Remove and discard the old gasket.

Inspect the sealing surface on both the upper and lower sections of the cylinder head for damage.

NOTE: Do not remove the exhaust valve capscrews.

Carefully place a new gasket on the lower section of the cylinder head.

Place the upper section of the cylinder head and insert five internal hex capscrews.

Tighten the internal hex capscrews. Use the following sequence.

NOTE: If installing a new air compressor cylinder head assembly, the following steps should not be performed. New cylinder head assemblies are already assembled per the instructions below. Skip to placement of the cylinder head assembly onto the air compressor housing.

Apply a light coating of assembly lubricant, Part Number 3163087 or equivalent, to the unloader plate recess of the cylinder head.

Place the unloader plate onto the unloader piston pinion, as well as the stationary pinion, and press the unloader plate into the assembly lubricant.

Install the air compressor intake valve.

Make sure the intake valve is oriented so the unloader channel of the cylinder head is exposed by four holes (1).

Install the sealing gasket in a similar manner.

Make sure to orient the gasket so the four holes are not blocked by the sealing gasket.

If a new head assembly is being installed, tighten the five small head cover bolts in the sequence shown.

NOTE: A new gasket kit must be used each time the air compressor cylinder head is removed and installed. Do not reuse the cylinder head mounting capscrews.

NOTE: Due to an interference with the fuel pump on some applications, following a specific installation sequence of the air compressor cylinder head and mounting capscrews will make installation possible with the air compressor still installed on the engine.

Before placing the cylinder head on the air compressor housing, insert the rear right capscrew (1) through the mounting hole. Place the cylinder head on the air compressor housing such that the right rear locating dowel and mounting capscrew engage the mounting hole in the air compressor housing.

Insert the rear left capscrew through the cylinder head mounting hole. Rotate the cylinder head clockwise into position, using the rear right capscrew and locating dowel as a pivot. Once the cylinder head has been properly set onto the air compressor housing, insert the front two capscrews.

Install the cylinder head and gasket.

Install the four 8-mm capscrews.

Tighten the capscrews in the sequence shown. Use the torque plus angle method.

NOTE: If a new head assembly is being installed, the five small head cover bolts MUST be tightened.

WARNING  Batteries can emit explosive gases. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To reduce the possibility of arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.

• Install the air inlet and outlet connections from the air compressor.
• Install the air governor or air governor signal line, if necessary. Refer to the OEM service manual.
• Install the air compressor coolant lines. Refer to Procedure 012-004 in Section 12.
• Fill the cooling system. Refer to Procedure 008-018 in Section 8.
• Connect the batteries. Refer to Procedure 013-009 in Section 13.
• Operate the engine and check for leaks.