ProbeGT-ZE

Okay so this is a bone stock '92 Civic Hatch w/ a D16Z6 swap (car is automatic). It started mysteriously overheating a few months ago and it's been parked since and I haven't had the time to work on it. The situation is that the upper hose gets hot but the lower hose stays cold. Of course the gauge sensor is in the upper housing and the thermostat/fan switch is in the lower housing. It shows indications of no flow. The whole cooling system aside from the waterpump itself has been replaced. Hoses, sensors, radiator, thermostat, clamps etc. Someone pointed out that it's probably a blown head gasket. I thought that too but there's no signs of that happening.

Even with a blown head gasket if the water pump was circulating coolant the lower hose would get warm eventually correct? I've replaced the thermostat twice and still nothing. Should I try removing the thermostat?

Dough_Boy.

A water jacket in the head could be blocked up. Or you could have got a defective thermostat.

ProbeGT-ZE

Hmmm....I've replaced the thermostat a couple times already...water jacket clog...cause?

Dough_Boy.

I couldn't even tell you. Antifreeze corrodes after a while. Maybe that could be it. when you took the hoses and thermostat off what did they look like?

ProbeGT-ZE

Pretty clean honestly. Some rust on the fittings but not enough to be a cause of concern.

JustaGSR18

could be the waterpump itself.. I have seen them go bad and the fins break off

Fabrik8

The only thing that you haven't replaced is the part responsible for circulating the coolant.

ProbeGT-ZE

Fabrik8 - any way to check the water pump without removing it?

Pele

Warm the engine up so the thremostat is open. Squeeze the upper hose and rev the engine. You should feel the pump add a little bit of pressure to the hose.

ProbeGT-ZE

With the engine running and the radiator cap open, if I rev the engine the coolant level does rise...that indicates a good water pump right?