Cummins ISX11.9 CM2250 – Service Manual 008-020   Cooling System Diagnostics

Use a pressure gauge with a maximum capacity of 414 kPa [60 psi].

Measure the coolant pressure at one of the OEM coolant ports in the coolant manifold located on the back of the cylinder head.

Operate the engine until the coolant temperature reaches 80°C [180°F].

NOTE: The thermostats must be open.

Operate the engine at rated rpm.

Compare the pressure readings to the following specifications.

Minimum Coolant Pressure at Rocker Housing

Coolant Pressure (Cap Removed)

If coolant pressure is high with the radiator cap removed, check the thermostat or radiator for a restriction. Refer to Procedure 008-042 in Section 8.

If the coolant pressure is low with the radiator cap removed, install a gauge with a maximum capacity of 69 kPa [10 psi] at the water pump inlet connection.

Operate the engine at rated rpm.

If the gauge reads more than 14 kPa [2 psi] with the radiator cap removed, check the radiator. Refer to Procedure 008-042 in Section 8.

If the gauge reads less than 14 kPa [2 psi] with the radiator cap removed, check the water pump or for engine coolant leaks. Refer to Procedure 008-062 in Section 8.