Temp gauge issues

Temp guage goes from normal temp to cold while passing on the highway and while going downhill, will not do this going up hill. I checked the fluid level and all is good any thoughts? Thanks!

 

Need to get a scan tool and see what the actual coolant temp reading is doing when the problem occurs and also if you have any codes.

I'm asuming you checked the level in the radiator and not just the overflow bottle correct?

 

Welcome!
I would start by checking the coolant level to make sure you are not low.
You may also get more help if you would include some details like engine, year, mileage, weather, etc. It could be the thermostat opening too soon.

GL

 

Got it! Thanks! Its 2020 tacoma TRD off road 3.5ltr 36k miles weather about was about 60°. I checked the coolant levels and all appears well. I should also mention that while in park I can rev the motor to 3000rpm and the temp guage will drop too. No codes or warning lights on

 

Fan clutch locked up ?

 

Fan works. On the way home today I finally threw a code, P0128. After reading about it ( https://www.700r4transmissionhq.com/p0128-toyota-tacoma/) Seems maybe a stuck open thermostat or a coolant temp sensor. Thermostat would make sense because coolant will flow through the motor all the time never allowing the moter to achieve proper temp.

 

seems strange the thermostat would die that soon. Having a good tech diagnose properly may end up cheaper than playing swap a part with it, but I'd guess a thermostat doesn't cost much,, it would probably come down to the time spent on changing it out,, not sure what that is, as I have never done it. Maybe look up a boobtube video on it and see if it's in your comfort zone.

 

The symptoms you described are that of a thermostat stuck open. I would do the following, although I have no idea if it will give you proper evidence because I have never done this in the Tacoma, only on older cars:

With the car dead cold, open the radiator cap, turn the engine on, you should see almost no coolant flowing inside the radiator, if you do, the thermostat is open when it should be closed.