Patriot 2WD L4-2.4L (2009)
Thermostat: Description and Operation
Engine Coolant Thermostat - Operation
OPERATION
When the Engine is cold and both the primary and secondary thermostats are closed. The coolant will circulate through the engine, heater system, and the
bypass. The cooling system has no flow through the radiator
As the engine warms up, the primary thermostat will start to open at 82 °C ( 179 °F). Coolant will start to flow through the radiator oil cooler and
transmission cooler. Coolant will flow through the transmission oil cooler only when the primary thermostat is fully open. The primary thermostat will
fully open at 95 °C (203 °F).
The secondary thermostat will start to open at 95 °C (203 °F). This will increase the coolant flow through the cylinder block and cylinder head and the
radiator. The secondary thermostat will fully open at 110 °C (230 °F).
If the thermostat is stuck open or allows coolant leakage through it, the engine will not operate at the proper temperature for obtaining engine fuel
efficiency, performance and emissions levels. If this condition occurs, a diagnostic trouble code will be set and a MIL light will be turned on. Refer to
the Powertrain Diagnostic Procedures manual for further information and diagnostics provided.
