Grand Caravan V6-3.8L (2009)
Thermostat: Testing and Inspection
ENGINE COOLANT THERMOSTAT
The thermostat is operated by a wax filled chamber (pellet) which is sealed. When heated coolant reaches a predetermined temperature the wax pellet
expands enough to overcome the closing spring and water pump pressure, which forces the valve to open. Coolant leakage into the pellet will cause a
thermostat to fail open. Do not attempt to free up a thermostat with a screwdriver.
Thermostat diagnostics is included in Totally Integrated Power Module's (TIPM) programming for on-board diagnosis. The malfunction indicator light
(MIL) will illuminate and a diagnostic trouble code (DTC) will be set when an "OPEN TOO SOON" condition occurs. Do not change a thermostat for
lack of heater performance or temperature gauge position, unless a DTC is present. For other probable causes,See: Testing and Inspection. Thermostat
failing shut is the normal long term mode of failure, and normally, only on high mileage vehicles. The temperature gauge will indicate this.
