Cummins/Onan — Coolant Thermostat - Remove and Install
Repair & overhaul
From a Cummins/Onan owner's manual covering: M11, M1i Series Engines, ps200da. Check it applies to your exact model before use.
Applies to: Cummins/Onan M11 engine
Before you start
- Do not remove the radiator cap from a hot engine. Wait until the temperature is below 50 C [120 F].
Procedure
- Remove the radiator cap after the engine is cool.
- Drain the cooling system: open the radiator draincock and remove the lower radiator hose.
- Remove the upper radiator hose from the thermostat housing.
- Loosen the coolant bypass hose clamps.
- Remove the four thermostat housing mounting capscrews and the thermostat housing.
- Remove the thermostat from the housing.
- Install the thermostat and a new seal in the groove on the housing mounting surface.
- Install the hose on the thermostat housing bypass outlet.
- Install the thermostat housing and four mounting capscrews.
- Install the upper radiator hose and tighten the bypass hose clamps.
- Close the draincock, install the lower hose, fill the cooling system.
- Operate the engine until it reaches 80 C [180 F] and check for coolant leaks.
Specs & values
- Thermostat housing mounting capscrew torque: 54 Nm [40 ft-lb]
- Coolant bypass hose clamp torque: 3 Nm [30 in-lb]
Source: Cummins/Onan owner's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.