Cummins ISX11.9 CM2250 – Service Manual 008-013   Coolant Thermostat

The engine thermostat and thermostat seal must operate properly in order for the engine to operate in the most efficient heat range. Overheating or overcooling will shorten engine life.

Use the following procedure to inspect the thermostat seal. Refer to Procedure 008-016 in Section 8.

WARNING  Complete this test with the engine coolant temperature below 50°C [120°F]. Hot steam can cause serious personal injury.

Remove the radiator hose from the thermostat housing.

Remove the coolant temperature sensor located on the rocker lever housing, toward the front of the engine, near the thermostat housing.

Install a thermocouple or temperature gauge, which is known to be accurate.

Install a hose of the same size on the thermostat housing outlet, long enough to reach a remote, dry container used to collect coolant.

Install and tighten a hose clamp on the housing outlet.

Place the other end of the hose in a dry container

Operate the engine at rated rpm for 1 minute.

Shut the engine off and measure the amount of coolant collected in the container.

The amount of coolant collected must not be more than 100 cc [3.3 fl oz].

If more than 100 cc [3.3 fl oz] of coolant is collected, the thermostat or thermostat seal is leaking and must be replaced. Refer to Procedure 008-016 in Section 8.

Complete the following test in-chassis to test the thermostat opening temperature.

Start the engine and monitor the water temperature and the container.

Thermostat Initial Opening Temperature

Shut the engine off when the coolant starts to flow.

If coolant does not start flowing into the container during the initial opening temperature range, the thermostat must be replaced.

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. If not reused, dispose of in accordance with local environmental regulations.

• Drain the cooling system. Refer to Procedure 008-018 in Section 8.
• Remove the upper radiator hose. Refer to the OEM service manual.
• Remove the coolant thermostat housing. Refer to Procedure 008-014 in Section 8.

Remove the thermostat from the thermostat housing.

Inspect the thermostat seal for cracks, corrosion, or other damage.

If the seal is damaged, it must be replaced. Refer to Procedure 008-016 in Section 8.

Inspect the thermostat for damage.

Suspend the thermostat and a 100°C [212°F] thermometer into a container of water.

Do not allow the thermostat or the thermometer to touch the sides of the container.

Heat the water and check the thermostat as follows:

The nominal operating temperature is stamped on the thermostat.

• The thermostat must begin to open within 1°C or 2°F of nominal temperature.
• The thermostat must be fully open to at least 11 mm [0.435 in] within 12°C or 22°F above nominal temperature.

The fully open distance between the thermostat flange and housing is 11 mm [0.435 in].

If the thermostat operates properly and more than 100 cc [3.3 fl oz] leakage is detected during the in-chassis test, replace the thermostat seal. Refer to Procedure 008-016 in Section 8.

Install the thermostat in the thermostat bore by pushing on the outer rim of the thermostat.

• Install the coolant thermostat housing. Refer to Procedure 008-014 in Section 8.
• The correct concentration of coolant additives must be used in the cooling system. Use the following procedure in the Operation and Maintenance Manual, ISX11.9 CM2250, Bulletin 2883444. Refer to Procedure 018-004 in Section V.
• Fill the cooling system. Refer to Procedure 008-018 in Section 8.
• Operate the engine until the coolant temperature reaches 80°C [180°F] and check for leaks.