Cooling efficiency is the system’s ability to move heat out of the engine at the rate the work puts it in. The radiator, the thermostat, the fan, and the water pump all have to do their share. A weak pump is easy to miss because the coolant level looks normal.
Flow problems show up as
- Temperature that rises only under load
- A radiator that is cool on one side
- Heater or cab circuits that stay cold
- Repeated thermostat replacements that do not help
Inspect the impeller if the pump is off. Erosion and corrosion cut the vanes down until flow is no longer enough. Replace hoses that are soft, and use the coolant specification for that engine. Mixed coolant attacks the pump and the oil cooler.
When you order, include the engine serial so the pump inlet and pulley match.