Is there a way to reasonably diagnose a water pump failure directly? In How to test the function of a water pump? the question is posed but the accepted answer only provides a way to infer that the pump is functioning:
Typically [with impeller failure], the engine will overheat, but the heater core and radiator will still be cold. With a thermostat failure, the radiator will be cold, but the heater core should still get hot. This leads to a possible false positive if the heater core is plugged and the thermostat failed.
A couple of questions have come up:
where it would be nice to have a way to confirm that the pump is working (at least in a qualitative way) without having to spill a lot of coolant or pull the pump.
Would it work, for example to:
- Squeeze one of the heater or radiator hoses and listen and/or feel for coolant movement (like kinking a garden hose to cut off water flow), or
- Listen with a stethoscope or screwdriver at a constriction or perhaps at a tee for the sound of rushing fluid – perhaps while adjusting engine speed.
It seems like if either of those methods would work they would make it possible to detect flow and decide if the pump was suspect.