My 85' 4runner has an overheating problem. So far it has gotten a new radiator, on the 2nd thermostat, new head (installed by a toyota shop), cooling system flush(by shop), and 10000 miles on the water pump. When the truck is warming up the temp goes over normal "3/4" then return to 1/4 of the way up. The gauge then rises steady when the heater is on..yes, "ON" It does not make sense to me, please help, thanks

 

its called temp overshoot, there is a special t-stat for it, here is a link to 4crawler's site to explain it
http://www.4crawler.com/4x4/CheapTri...tml#Thermostat

 

Mine does the exact same thing...now that I know why I don't worry about it. Next time I have to replace the t-stat, I'll get the special one.

 

Yep, temperature overshoot problem. Mine has been totally fixed once I installed the dual valve t-stat. Added benefits of that t-stat are that it works very well, small valve has a much faster thermal response time and even the large valve works faster than the single large valve t-stat. And it just lasts and lasts, I have about 7 years on my original one, it is still working fine. And there is a built-in redundancy in that if one valve fails the other one can still handle temperature regulation. Even if I did not have the temperature overshoot problem, I would still run this t-stat, it is just a superior design.

 

Yep, sounds like the thermostat. My friends mazda used to do the same thing until we replaced it.

 

I have the same problem, I will get the new thermostat...

 

Thanks so much for the info, on my way to buy it right now, thank you