M11 Plus Series Engines Operation and Maintenance Manual – 008-013   Coolant Thermostat

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 coolant system pressure cap. Heated coolant spray or steam can cause personal injury.

Remove the pressure cap when the engine is cool.

WARNING  Coolant is toxic. If not reused, dispose of in accordance with local environmental regulations.

Drain the cooling system. Refer to Procedure 008-018. (Cooling System) in Section 6.

Remove the upper coolant hose from the thermostat housing.

Loosen the coolant bypass hose clamps.

NOTE: Some models could have a converter cooler disc located in the bypass hose. Contact a Cummins Authorized Repair Location.

Remove the four thermostat housing mounting capscrews and the thermostat housing.

Remove the thermostat from the housing.

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

If the seal is damaged, it must be replaced. Contact a Cummins Authorized Repair Location.

Inspect the thermostat for damage.

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

NOTE: Do not allow the thermostat or thermometer to touch the container.

Heat the water, and check the thermostat as follows:

The nominal operating temperature is stamped on the thermostat.

• Thermostat must begin to open within 1°C [2°F] of nominal temperature.
• Thermostat must be fully open within 12°C [22°F] of 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 in-chassis test, replace the thermostat seal. Contact a Cummins Authorized Repair Location.

Install the thermostat in the housing.

Install a new o-ring seal in the groove on the thermostat housing mounting surface.

Install the hose on the thermostat housing bypass outlet.

Install the thermostat housing and four mounting capscrews.

Tighten the mounting capscrews.

NOTE: If a torque converter cooler disc is used in the coolant bypass hose, contact a Cummins Authorized Repair Location.

Install the upper coolant hose to the thermostat housing outlet. Tighten the hose clamp.

Refer to the OEM service manual for the correct torque value.

Tighten the coolant bypass hose clamps.

Close the cooling system draincock, and install the lower coolant hose.

Tighten the hose clamp.

Refer to the OEM service manual for the correct torque value.

The correct concentration of coolant additives must be used in the cooling system. Refer to Procedure 018-004 (Coolant Recommendations and Specifications) in Section V.

Fill the cooling system. Refer to Procedure 008-018 (Cooling System) in Section 6.

Operate the engine until it reaches 80°C [180°F], and check for coolant leaks.