The water pump pulls coolant from the bottom of the radiator and pumps it through the engine back to the top
of the radiator for cooling. Reduced or interrupted flow will result in the engine running hot.
The pump is belt driven from the crankshaft pulley. An automatic belt tensioner is used to prevent the belt from
slipping on the pump pulley. A malfunction of the tensioner will cause the water pump impeller to rotate at a slower speed reducing the amount of coolant flow.
The coolant flow can also be reduced if the inlet hose to the water pump collapses. A hose will usually not col-
lapse while the engine is running at low speed. Check the hose while the engine is running at rated speed.
NOTE: Be sure the engine is warm, a minimum of 95°C [203°F], so the thermostat is open.
A worn or malfunctioning water pump will not produce the flow required to prevent the engine from running hot.
However, be sure to check the other possibilities indicated in the Troubleshooting Logic before checking the
flow or replacing the pump.
As stated in the coolant discussion, an obstruction in the passages can interrupt flow.
