I'm curious for updates as well. My temperature gauge seems to be all over the place. At highway speeds it's about 1/4 of the way up the scale, and now at normal driving it's about 1/8 on the scale. It's pretty dang low. Just put in a new thermostat and gasket too.

 

Make sure you put in Toyota t-stats.
22re - 190 degree
3vze - 180 degree

That simple fact just saved my ass from digging any deeper into my overheating problem.

 

Mine was an 88 degree Celsius thermostat, which converts to 190 degrees Fahrenheit. So I got that much right.

 

Just to jump in on this...Mine (22re) has been running just above the cool line for the past few months. I put on the heat the other day and low and behold the truck almost came up to normal temp. The past few morning's I have been using the heat and the truck warms up more. when I head home I don't run heat and it's back down to just above the cool line. Isn't that interesting???

Now back to our regular scheduled thread...

The only other thing I can think of is that the pump may not be pumping...but that would mean it should over heat in the city driving...I'm starting to run out of ideas...

 

i think i found an explanation for my problem. the day after i first experienced this problem i checked the coolant level and it seemed to be ok. the next day the problem happened again so for kicks i topped off the coolant, turns out was able to add about another quart. drove it again the next day and noticed a small pool of coolant underneath the front of the vehicle. i checked and saw residue from a small coolant leak on the backside of the lower radiator hose.

my guess is there was a slow coolant leak from the lower radiator hose that occurred mostly while driving. over time the low coolant level reached a certain point where there was an air pocket that built up where the temp sensor is, the hot air being much much hotter than the coolant would cause the erratic behavior in my temp gauge. this explanation makes the most sense to me but i'm open to being wrong. from everything i have experienced and read, water pumps and thermostats either work or they don't, they don't behave erratically.

i am keeping a close eye on the coolant level and will replace the lower hose this weekend. last thing our touchy 3vz-e motors need is high temps. thank all of you for your help!

 

Nice find!!! Hope this quick fix clears this up for ya.