Voyager L4-2.4L VIN B (2001)
Thermostat: Testing and Inspection
DIAGNOSIS AND TESTING - 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 Powertrain Control Module'S (PCM) 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. Thermostat failing shut is the normal long term mode of failure,
and normally, only on high mileage vehicles.
