The_One

Hey folks,
I just got back from a trip a few thousand kilometres up north of Western Australia. Took the 4Runner down the coast where there is no one for miles and miles. Ningaloo Reef is offshore there and the snorkelling is world class.


Anyway, on the way back the 22R is getting a bit hot when idling.
The air being pulled through the radiator by the fan is cold, unless i rev it up above about 1,000RPM - then the radiator gets hot and the fan pulls through hot air.

It looks like it could be the water pump, and it is only moving enough water at higher RPMs. However how could the water pump fail in this way? I have read that the impeller can disconnect from the shaft and only work at low RPMs but my problem is the opposite...?

The thermostat is the other suspect - perhaps not opening enough and having to have higher RPMs to force enough water through. But i had it out and tested it a few weeks ago and it seemed fine.

Any thoughts guys?
Thanks!

RAD4Runner

Yes, sounds like a bad water pump. Perhaps getting weak already and t takes higher RPM for it to move water enough to cool the engine.

The_One

Thanks. It does sound like the water pump - but does anyone know how do the pumps fail that would cause this symptom?
Impeller loose or something? The pump was put in by the bloke before me, and it is one of those cheap stamped steel ones, not a cast impeller. How would the pump work one minute and then only work at higher RPMs?