I have an 1986 4Runner that I just noticed will start to get hot, then cool off. It never overheats, but the temp gauge just keeps fluctuating instead of staying at one temp. Anyone else have this happen? I wonder if its my thermostat going out???? Any help is appreciated. Thanks.

Dan

 

I would start with the thermostat first it is easy to get to.

 

If the thermostat doesn`t fix the problem, try replacing the temp gauge sending unit, when they go bad it can cause the temp gauge to read wrong or bounce around.

 

An other thing that can cause it but I have yet to see in a toyota is having the propeller on the water pump so rotted or corroded that it is not moving the water properly. The symtoms are normally it will get hotter at an idle/low rpms and cools down at high rmps.
If your shroud is missing it will heat up at a stop/low speeds and cool at high speeds.
I have also read that there is a clutch on the fan that could cause this if it was starting to go.

 

i have sort of the same problem on my 91 4runner 3.0 when im cruising shes fine but if im stopped in traffic the gauge goes up to hot but when i get going it usually cools down. another question when i shut it off and it has cooled down i look in my rad and there is no coolant in there and im not sure where its going as i can see no visable leaks or anything and my head gasket was done at 300000 kms and im at 350000kms so i dont think its burning it or anything. I also have duct tape on my air intake tube and my friend was looking and someone said that my truck could be running too lean and burning hot?? not sure what to do .. PLEASE HELP!!

sorry for the long post :s

 

First I would replace the radiator cap. When they go bad it can cause a loss of coolant without any signs.

 

Thanks guys, it is not an issue of speed or idle. It does this as I am traveling at a constant rate of speed. I am guessing it is the thermostat, I will swap it soon and see.

 

make sure to get an oem t-stat! you will be glad you did!