Thermostat ???

Thermostat Issue??

2015 Toyota Tundra........Temp Gauge is normal, then all of a sudden it pegs all the way to "Hot", the alarm in the Dash flashes, then the needle goes right back to normal temp. Does this once or twice each week. Is the Thermostat about to Fail?? Sensor?? Battery?? Not sure what it could be.

 

check coolant level.
Check for stuck thermostat. Just replace it and be sure jiggle valve is at 12 o’clock.
Check your fan clutch by spinning fan with engine off.

 

When mine did that - it was the temp sensor.

 

Good point @Johnsonman

 

Thanks for the info Guys!!

 

^ I concur with @bfunke and @Johnsonman - sound like a sensor issue. It takes longer than a few seconds for the truck to build heat like that, but a bad sensor or a pocket of steam from low coolant would do it.

 

First thing to check is the obvious and most dangerous. If it’s low coolant, it’ll do exactly that. Rule that out asap. You risk catastrophic damage.

when that’s ruled out, move on with the rest of the list.