Cummins ISX11.9 CM2250 – Service Manual 020-024   Engine Brake

Features of the engine brake:

1. Solenoid
2. Location for mounting studs
3. Location for Cummins® harness p-clip
4. Slave piston adjusting screw
5. Slave piston
6. Location for mounting capscrews.

The engine brake master piston contacts a machined pad (1) on the exhaust rocker lever (2).

The ISX11.9 CM2250 engine is available with either a 12 volt or 24 volt electrical system. These systems use different engine brake solenoid valves.  The 24 volt solenoid valve has one terminal and is grounded to the body of the solenoid. The 12 volt solenoid valve has two terminals and is grounded to the wiring harness.

A stuck oil flow solenoid valve can prevent the engine brake from operating or performing properly.

To check for a stuck solenoid valve, disconnect the electrical connection to the engine brakes and operate the engine.

If exhaust gases can be heard escaping past the valves, the solenoid valve or valves must be replaced. Contact an authorized engine brake dealer.

An incorrectly adjusted or damaged slave piston will cause the engine to run rough or not to start.

To check the slave piston, remove the rocker lever cover. Refer to Procedure 003-011 in Section 3.

Check the slave piston clearance.

Use the Adjust section in this procedure to measure and adjust the clearance.

Inspect the slave piston for damage.

If the slave piston is damaged, contact an authorized engine brake dealer for repair.

Install the rocker lever cover. Refer to Procedure 003-011 in Section 3.

If a sudden drop in lubricating oil pressure causes the engine to not start or run rough, perform the following steps.

• Remove the rocker lever cover. Refer to Procedure 003-011 in Section 3.

Check for the following:

• Upper solenoid valve seal ring missing or damaged
• Oil supply adapter o-ring missing or damaged.

Contact an authorized engine brake dealer to correct the problem.

Install the rocker lever cover. Refer to Procedure 003-011 in Section 3.

If the engine is misfiring or has a loss of power:

• Remove the rocker lever cover. Refer to Procedure 003-011 in Section 3.
• Use the Adjust section in this procedure to measure and adjust the clearance.

Install the rocker lever cover. Refer to Procedure 003-011 in Section 3.

• Remove the rocker lever cover. Refer to Procedure 003-011 in Section 3.

Disconnect the solenoid power and ground wires from the terminals. Refer to Procedure 019-063 in Section 19.

Remove the mounting capscrews from the intake side of the engine brakes and the mounting hexagonal nuts from the mounting studs.

Lift the engine brake housings off of the studs.

Remove the mounting spacers from the mounting studs.

Remove the mounting studs.

NOTE: If the engine brakes will not be installed again, remove the oil supply adapters and plug the oil supply ports in the rocker lever pedestals.

Secure any loose wires in the wiring tray.

WARNING  When using solvents, acids, or alkaline materials for cleaning, follow the manufacturer’s recommendations for use. Wear goggles and protective clothing to reduce the possibility of personal injury.

WARNING  Wear appropriate eye and face protection when using compressed air. Flying debris and dirt can cause personal injury.

Use an approved solvent to clean the brake housings.

Dry with compressed air.

Inspect the housings for any missing or damaged parts.

Inspect the solenoid and terminals for damage.

With the solenoid removed from the housing, check the operation of the pin assembly. This should be totally free.

• Remove the inlet screen
• Hold the solenoid with a thumb on the bottom pin and an index finger on the button.
• Alternately push on the button and pin. The pin and button should move together freely.

Check the resistance across the solenoid terminals with an ohmmeter.

• 12 volt dual lead solenoid
• Cold engine (25°C [77°F]) – 8 to 10 ohms
• Hot engine (121°C [250°F]) – 16 to 20 ohms
• 24 volt single lead solenoid  32.6 – 39.8 ohms

Replace the solenoid if the measured resistance is not within the above specification.

Check that the screen is not torn or damaged.

Check the connector for wear on both terminals.

Check for damaged or worn solenoid o-rings. If the o-rings can not be reused, replace the solenoid assembly.

Check that the solenoid is seated in the bore before tightening.

Tighten the solenoid hold-down screw.

Check that the wire harness connector is secured to the studs.

Tighten the fasteners.

If the solenoid does not meet the above criteria, the solenoid must be replaced. Contact an authorized engine brake dealer to correct the problem.

Apply a thin film of clean 15W-40 oil to the machined surfaces.

Inspect the oil supply adapter o-rings for damage.

Inspect the mounting studs and spacers for fretting and other damage.

Inspect the master piston retention springs for damage.

Inspect the exhaust rocker brake actuating pads to see if they are missing or damaged.

Check that the correct wiring harness is installed. The engine can be equipped with either a Brake harness or a Non-Brake harness.

Install the correct harness if not present. Refer to Procedure 019-063 in Section 19.

Check that the compression brake crossheads are installed and verify the actuator pins are facing the camshaft side of the engine.

Oil feed adapters must be installed in the rocker lever pedestals. If the oil feed adapters are not installed, perform the following:

• Remove any pedestal plugs from the oil feed drilling
• Be sure o-rings are undamaged and installed on the adapters
• Install the oil feed adapters into rocker lever pedestals.
• Tighten the oil feed adapters.

Install six mounting studs into the holes in the cylinder head. The allen socket should be pointing up.

Hand-tighten the studs until bottomed in the tapped hole.

Install a mounting spacer on each stud.

Install the brake housing marked “Front” onto the studs for cylinders 1 through 3.

Install the brake housing marked “Rear” onto the studs for cylinders 4 through 6.

Install the mounting capscrews and washers through the left side of the brake housing and into the rocker shaft supports.

Install the mounting nuts onto the mounting studs.

Snug all fasteners.

Tighten the mounting hexagonal nuts and mounting capscrews starting with the center fastener and working outward, as shown in the illustration.

Tighten the engine brake mounting capscrews.

Connect the solenoid power and ground wires to the terminals and tighten.

Adjust the slave piston clearance. Use the Adjust section in this procedure.

CAUTION  Do not tighten the adjusting screw too tightly. The engine can be damaged.

CAUTION  Failure to have the correct clearance can damage the engine.

To obtain maximum brake operating efficiency, and prevent engine damage by piston-to-valve contact, complete the following instructions carefully.

Adjust the exhaust valves on the appropriate cylinder. Refer to Procedure 003-004 in Section 3.

After adjusting the exhaust valves on the appropriate cylinder, insert the correct feeler gauge.

Loosen the locknuts on the slave piston adjusting screws.

Rotate the engine to the desired position marked on the front engine damper.

Use Cummins® service tool, Part Number 4919693, to adjust the brake lash for the corresponding cylinders to 3.8 mm [0.150 in] of clearance.

Once properly adjusted, hold the adjusting screw in position and tighten the locknut.

After the secondary piston adjusting screw locknut is tightened to the correct torque value, check the clearance with the feeler gauge again.

• Install the rocker lever cover. Refer to Procedure 003-011 in Section 3.