Water Pump: Testing and Inspection

DIAGNOSIS AND TESTING - WATER PUMP

A quick flow test to determine if the water pump is working effectively is to check heater system for proper operation. A defective pump will not provide an adequate flow of heated coolant through the system.

WARNING: DO NOT REMOVE THE COOLING SYSTEM PRESSURE CAP WITH THE SYSTEM HOT AND UNDER PRESSURE BECAUSE SERIOUS BURNS FROM COOLANT CAN OCCUR.

Another flow test to help determine water pump operation is as follows:

1. Remove cooling system pressure cap.
2. Remove a small amount of coolant from the system.
3. Start the engine and warm up until thermostat opens.
4. With the thermostat open and coolant level low, visually inspect for coolant flow. If flow is present, the water pump is pumping coolant through the system.

WATER PUMP TESTING - OM 651

1.



A water pump slide valve test is use to ensure valve movement and proper flow from the water pump. The water pump valve is controlled by a switch that receives a signal from the ECM. When the switch is turned on. Vacuum is supplied to the water pump that actuates a valve that controls the flow of coolant on or off. Using a vacuum pump on the port located on the water pump. When vacuum is applied, the piston should be heard by means of a clunk. It is possible to see movement of the valve through the weep holes located around the housing of the pump. A return spring will slowly return the valve.
Once the water pump is verified of proper operation. The vacuum supply can be checked by means of a vacuum gauge installed on the supply line before and after the switch. This will verify if the vacuum pump or if the switch is working properly. Vacuum should be 18 inches HG (609 millibars).
Once vacuum has been verified. While manually applying and releasing vacuum. Perform theWATER PUMP test.