99 tacoma v6 overheating

Unless you have the TRD 170° thermostat you should be opening fully around 185-195. It's just an expanding wax pellet that opens the stat, I always boil mine first to see when they open, I've had bad Toyota ones right out the box. But they typically maintain somewhere from 185-200 on a 5VZ. In the summer I hover at 194 and winter it doesn't even get there unless I idle off the highway for a long time. But climbing a grade (I'll push that shit to 4500rpm to keep hauling ass) it will climb up to 210. Some of the guys I wheel with have 5VZs that are always at 195-205, there's a tolerable variance.

 

Here’s fsm page

 

I haven't seen any open much if any before 180°. But I suppose it would be okay if it did