I haven't visited this group in a long while. I have been a Toyota owner for 32 years, starting with a Corolla 1200, brnad new when I was in H.S. I currently have an '85 Corolla GTS I bought in April of '86, an '88 Supra I bought a couple years ago, and a Scion tC I bought in September. The Supra is a Sport Roof (Targa) and goes into the garage after the first 50 degree day until spring. The Scion is a Daily Driver, and the Corolla is my favorite car, but needs some repair.
At any rate, this has NOTHING to do with any of my Toyotas! I had an AWD Grand Voyager I was using as a Winter Beater, but after braking off some bolts in the failing engine, I bought an 89 Mazda 626 for $150 from a friend. It needed about $500 worth of work and parts, and is a pretty decent car. I did a lot of the work myself.
One of the things I did myself was a cooling system flush. I flushed the system as usual, and then flushed it again since the AF was REALLY rusty. When we originally started the car, we let it run for 1/2 hour, and the temp needle never moved from 1/3 of the way up the gauge. After the flush and fill, it would get to half and then the fan would kick on. As long as the car is idling...
When the car is in motion, the gauge hardly moves above the lowest mark on the gauge. If I leave it running while going into a convenince store, it will get up to the 1/3 mark like it did when we first started it, but then drops back to Cold when the car starts moving.
Since it seemed like a stuck thermostat, I changed that the next day. No luck. I tried a new radiator cap. Still no good. I replaced the water pump when I replaced the timing belt. Uh-Uh...
If the car is left to sit and run, the gauge moves up and there is PLENTY of heat. But, as I said, when the car starts moving, the temp goes low. AFAIK, the thermostat is installed properly. Before I go through the trouble of removing it again, can anyone think of something I overlooked? The radiator and the overflow bottle are full, water circulates with the water pump, temp sending unit seems OK, fan comes on when it should and is off when it should be, everything seems to check out OK. I'm stumped. I even have a piece of cardboard blocking about 1/3 of the radiator.
I'm about to start banging my head against the wall!
All this 'cause I don't want to drive my Scion in the snow! Hey, at least the Supra has heat!