Thermostat: Testing and Inspection
WATER THERMOSTAT TESTWARNING: Never remove the pressure relief cap under any conditions while the engine is operating. Failure to follow these instructions could result in damage to the cooling system or engine and/or personal injury. To avoid having scalding hot coolant or steam blow out of the cooling system or reservoir, use extreme care when removing the pressure relief cap from a hot cooling system or reservoir. Wait until the engine has cooled, then wrap a thick cloth around the pressure relief cap and turn it slowly until pressure begins to release. Step back while the pressure is released from the cooling system. When certain all pressure has been released (still with a cloth), turn and remove pressure relief cap.
When investigating a concern of overheating or of insufficient heater/defroster performance, perform the following:
1. Check and service any leaks found in the:
a. Radiator pressure relief cap.
b. Heater water hoses.
c. Radiator hoses.
d. Water hose connection gasket.
e. Cylinder head.
f. Water pump housing gasket.
2. Check the cold engine coolant level in the radiator coolant recovery reservoir.
a. If the level is below the cold fill level, fill to the cold fill level with a 50/50 mixture of Ford Premium Cooling System Fluid E2FZ-19549-AA or -B (in Canada, CXC-8-B) or equivalent meeting Ford specification ESE-M97B44-A and water.
b. If the coolant drops below the cold fill level, add coolant to bring level back to the cold fill level. If air is suspected in cooling system, perform Cooling System, Draining, Filling, and Bleeding procedure.
3. When this procedure has been completed, feel the heater inlet and outlet hoses and the underside of the upper radiator hose. The water thermostat should be replaced only if these hoses are cold after 10 minutes of operation.