Abnormal Overheating

[LeeRoy]

Why can’t it measure the temperature of air? It reads temp as you said, how would it know whether it’s immersed in water or air?

As EldarO said water has different properties to air hence an incorrect reading.

On a similar note the low fuel light is triggered by a coil of wire sitting on the fuel sender assembly in your fuel tank. As you know, heat affects resistance, and this coil has current running through it so it gets hot, when immersed in fuel it gives a low resistance but once your tank becomes empty and its only air that resistance rises and triggers the light to come on.

[-GT-]

As EldarO said water has different properties to air hence an incorrect reading.

Agreed, wasn't trying to say it would read correctly, just that it wouldn't read full cold.

[Vios-GT_07]

i'd say check to see if it's got BHG first (in case you didn't get the hint about 7Ms)

but yea your symptoms sound a lot like the thermostat is wide open, or the thermostat gasket (little rubber ring thing around the thermostat) is broken and allowing water to go around it... that made a big difference on my 4A-G corolla, and had symptoms you described as well

every post above is good so try them out !

[andylaurel]

thanks for the advice guys
I will replace the thermostat, the radiator cap and install an aftermarket water temp guage.
I will also flush the radiator.

[jimmmayyy]

A thermostat is only there to hold water in the block for cold starts, so it wouldn't really cause it to overheat. Sounds like air pockets to me, since you say you just filled it up. With the car running (not hot) find the highest point where there is coolant and crack it until you get a clear stream with no more bubbles coming out. Not sure on your engine whether it has a specific bleeder built into it anywhere, but if theres not, find the highest coolant line and let it bleed. with the radiator cap off too. Eventually all the bubbles will work their way out the overflow however.