1990 Protege Overheating

[j369852147412]

I have a 1990 with 174k miles that overheats (needle goes to below H) when I idle (e.g. stop and go traffic) in 90-100 degree weather. And even sometimes when I have to do stop an go driving on the hills of san francisco when the ambient temperature is 55 degrees. Once i start moving (above 20mph) the needle goes back down to the middle. The thermostat has been replaced a few weeks ago, and I checked the fan switch and it is working properly and the fans do come on. I also pinched both the inlet and outlet hoses of the radiator and I can feel that there is water flowing through.

Water pump is fairly old, but it has zero leaks at the moment. Radiator is about 5 years old.

[Mazda_Powered]

Sounds like a water pump to me if your rad isn't starting to get clogged. If your fan is coming on, your not losing coolant, and the t-stat is operating properly...you have a flow problem.

I'd try to backflush the radiator and see if that helps, could have fine particles starting to clog it up.

[1st Gen]

The temp sensor on the thermostat is the one that controls when the fan comes on. Next time it get's hot and you're in the drive through, jump out and see if the fan is on. If it's hot and the fan isn't on, that sensor is foobar. Assuming there's coolant in the system and it's circulating.
Next time it gets hot, turn on the heater full blast. If the air is hot, it's the sensor. If it's cold, it's coolant level/circulation.

The wire that goes to that plug is solid and it's fragile. So is the plug. So, be careful if to F with it.

[j369852147412]

My fan does come on when it's hot. I actually broke the wire that goes to the temp sensor on the thermostat housing, but i took the plug completely apart and resoldered it and the fan still comes on when it's hot. The air is hot when I turn the heater on. The car also warms up very quickly. Im thinking it's mostly likely what Mazda_Powered said. Probably a flow problem. If my waterpump isn't leaking, how could a old/dying pump not circulate water?

AFAIK the pump impellers are metal, and it's just a straight shaft from the impeller to the pulley on the outside with a series of bearings and seals in between. I've double checked and my coolant levels are good and there are no leaks.

[FE3-323]

did you try flushing your whole system really well.

[j369852147412]

So I pulled out the radiator and flushed it in reverse. Water in from the bottom and I let the water come out of the top and fill cap. The water was slightly brown for a bit and then turned clear so I hoped that helped. I also completely flushed the system today and put in some new coolant.

[Mazda_Powered]

awesome! sounds like you're on your way to solving the issue.

Water pumps have a tendency to have blade failure due to the PH level in the coolant, to acidic, and it will actually cause the blades to rust and wear down to where they can't flow a damn thing. So keep that in mind unless you know the pump has been recently replaced lol.

[1st Gen]

Back in the day at Dad's old repair shop he'd show me water pumps that had been eaten by electrolysis. It's pretty crazy. Different material now but---.

[93BlkOnGreenPro]

Someone also suggested to me to tack weld the propeller of the new wp to the shaft bc alot of the auto zone / advance cheap wp, the propellers have been coming off with low miles.

Just a thought if you are not buying a oem unit.

[j369852147412]

So today the ambient temp was around 60 degrees, and i was going up a few hills revved it up to 4-5k for each long stretch of hilly road. And at the tops when i stopped at stop signs. The temp gauge went to 3/4 again. So now im deciding whether it's the radiator or the waterpump.