After Repairs Operational Check

COOLING SYSTEM OPERATIONAL CHECK

IMPORTANT: Always verify the operation of the thermostat and cooling fan prior to driving the vehicle after a cooling system repair.

HOW
- With the cooling system filled and bled and the expansion tank cap installed, start the engine and allow the coolant to warm up.

Thermostat Shut:

- The lower radiator hose should remain cool to the touch until the coolant within the engine block and head has reached the thermostat opening temperature.

Thermostat Opens:

- The thermostat opening should be indicated by a rapid warm up of the lower radiator hose.
- If lower hose gradually warms up, the thermostat may be stuck open (assuming the engine is started cold)
- If the coolant temperature reaches the normal operating temperature (as indicated by the temperature gauge) before the lower hose becomes warm, the engine should be turned off, and the cooling system allowed to cool down. The thermostat may be stuck closed and should be removed and tested.




WARNING: Never remove the radiator cap, or disconnect a coolant hose on a warm engine. A warm cooling system may contain a large amount of stored energy in the form of steam and high pressure, which could seriously injure you.

- If the thermostat opens properly, continue to allow the cooling system to warm up. As the coolant temperature reaches its maximum operating temperature the electrical cooling fan should energize. Verify the fan energizes and de-energizes.

WHY
Thermostat Closed, Cold Engine - With the thermostat closed, coolant flow through the radiator is blocked forcing the coolant to re-circulate through the block and head. This allows for a rapid warm up. During this time there should be little or no coolant flow through the upper radiator hose.

Thermostat Open, Warm Engine - Once the coolant has reached normal operating temperature, the thermostat begins to open, allowing coolant flow through the upper hose and into the radiator. The thermostat will continue to regulate the amount of coolant flow to the radiator to maintain a optimum operating temperature.