M11 Series – Service Manual – 008-020   Cooling System Diagnostics

This procedure tests the correct operation of the fan, shutter, coolant temperature gauge, and thermostat. It also checks for combustion leaks into the cooling system, coolant flow through the filter, and entrained air in the system. Carefully read and understand all the following steps before beginning the troubleshooting procedure.

This is a free-running (non-dyno) test. It requires the use of the coolant pressure/temperature/flow analyzer kit, Part No. 3822994, and the proper installation of the cooling system Compuchek® fittings located on the engine.

WARNING  Do not attempt to install fittings unless the coolant temperature is below 49°C [120°F]. Failure to do so can cause personal injury from heated coolant.

The coolant

must not be drained to install the fittings. Draining the engine can introduce air into the system and give false results.

Required Engine Sensor Fittings

The water pump inlet pressure line of the analyzer kit

must
be installed on the water pump inlet Compuchek® fitting on the rear cover of the water pump.

The thermostat housing pressure line of the analyzer kit can be installed in one of the following Compuchek® fitting locations:

• The heater housing on the rear of the water header plate
• The outlet fitting on the water pump.

This connection will enable the operator to record cylinder block pressure.

The remaining line of the analyzer kit

must be plugged.

Remove the radiator cap, and leave it off for the following test.

NOTE: All cab heaters and air conditioners

must be turned off, and the engine fan control

must be turned to the Automatic position if applicable.

Install the combustion gas leak test instrument, Part No. 3822985.

Refer to Procedure 008-019.

Install the analyzer kit, Part No. 3822994.

• Red Line – Plugged
• Yellow Line – Cylinder Block Pressure
• Black Line – Water Pump Inlet.

Pressure Readings
– Turn the pressure selection valve to the position corresponding to the desired reading. Turn the temperature selection valve to the “OFF” position.

NOTE: When the cylinder block pressure reading is taken, the valve

must
be turned to the thermostat housing pressure location. This is due to the different hose connection used on the M11 and L10 engines.

Monitor the sight glass installed on the service tool throughout the test. If air is observed, finish the test and examine the combustion leak tester. This will determine the origin of the leak. Refer to Procedure

008-019.

Temperature Readings
– There will be temperature fluctuations when switching the temperature selection valve. This fluctuation is normal, and is caused by temperature loss in the line. The temperature will stabilize after a few seconds.

Check the color of fluid in the combustion gas leak tester. This information, along with the sight glass observations, will help isolate the source of air in the cooling system, if any.

Refer to Procedure 008-019.

Do

not rule out combustion gas leaks if the combustion gas leak test does

not indicate a combustion gas leak. The test kit is

not sensitive enough to detect very small combustion gas leaks.

Check the recorded coolant temperature when the shutters are opened. Compare this value to that which is stamped on the shutter control. Cummins Engine Company, Inc. recommends that the shutters open at 85°C [185°F].

Check the recorded coolant temperature when the fan is engaged. Compare this value to that which is stamped on the fan control. Cummins Engine Company, Inc. recommends that the fan engage at 96°C [205°F].

Compare the cab temperature gauge reading with the block temperature. Replace the cab temperature gauge if it is

not within the manufacturer’s specifications of the correct reading. If no manufacturer’s specifications are available, replace the gauge if it is

not ±3.9°C
[7°F] of the correct reading.

Read the recorded block pressure at 60°C [140°F]. If the block pressure is less than 138 kPa [20 psi] at high idle and without a pressure cap, check the following:

• Remove the water pump, and inspect the impeller’s integrity and for slippage on the shaft.

If there is a drop in block pressure of more than 34 kPa [5 psi] during the test, check the following:

• Air in the system.

  Refer to Procedure 008-019.

• Incorrect initial cooling system fill.
• Less than 50/50 antifreeze mixture, or the engine is at high altitude.