So, i must replace the thermostat from my 4th gen 3S-GTE. I was doing some research around the web and i found the part number for this thermostat, is: 90916-03100. This one can be found in the 2UZ-FE, 3SGE from 94-99 Celicas, from the ST205 3S-GTE (94GT-Four) and from the Caldina ST215 4th gen 3S-GTE. I found those engines that shares the same thermostats! i dont know if another engine use the same one.
The 90-93 3SGTE (2nd Gen) do not share the same thermostat!.

I just post it for the record! and to give a little info

Fran

Make sure to order

16346‑17010 GASKET, THERMOSTAT

with it. Your old thermostat gasket may not hold a good seal.

Unless you buy the TRD thermostat which already includes a gasket. The genuine item does not.

Yup nice info! i forgot to put that!... Yup i buy the gasket with my new thermostat!

How do you know when it has to be changed?

when it takes a really long time for the engine to warm up, or if it overheats. a broken or stuck open thermostat will cause the engien to take much longer to warm up and on super cold days, it might not warm up at all. if its stuck closed the water cant flow and it will overheat

Really easy way to tell is if your temperature gauge drops while in motion, then rises when idling.

I heard that if your car doesn't blow hot air through the vents after driving for a good amount of time its probably a thermostat as well?
Could be wrong, can anyone confirm this?

Yeah that's right.

It's also a good idea to flush the heater core at the same time as changing the thermostat, I've had the thermostat stay open before and replaced it and heater still never worked until i took it all apart and flushed the heater core aswell.

>

This happened to me, I knew it was the thermostat. I'm going to buy a new one soon, but do you know WHY it does this?

The thermostat stays shut by a spring, and there's a diaphragm filled with wax inside it. The wax expands to a certain point with heat causing it to push open the thermostat letting cool water pass through.

After a good overheating or boilover, an old thermostat can get stuck (in most cases stuck in the open position) thereby constantly cooling the engine and not regulating the temperature. This means when the car is moving, a big flow of air across the radiator brings the temperature right down, and the thermostat can't close to compensate, you'll also notice the heater doesn't work because the engine is always cold.