The temp. gauge in my SR5 cluster started going crazy today. I started the truck and was driving about 5 minutes, just long enough for it to get to normal operating temperature. The needle then started jumping from normal to the red and back to normal very rapidly. It continued to due this until I got to where I was going, about 2 minutes farther, then stayed in the red.

Coolant level is full, no water in the oil.

Thanks for the help.

 

what year truck is this in?

Its a common problem for the temp gauge to break in sr5 clusters in 85-89 trucks/4runners. see if you can tap the gauge while its on to see if that makes it move, indicating that it is broken (or having issues like mine)

If tapping the gauge doesn't make it move (tap the lower corner of the platic cover, but not hard, you don't want to break anything else) take a look at this:

http://www.4crawler.com/4x4/CheapTricks/index.shtml

Scroll down to where it says thermostat and check it out

More info would help so let us know what you find!

 

you don't mention any idle fluctuation so yes it sounds like the gauge is simply malfunctioning...

did it appear that the truck was actually running hotter than normal? Was there a recent coolant changeout? If so it may need burped...it can appear full but have an air pocket-this is somewhat common on the 22re.