so I have a 1997 4runner limited with 190,000 miles on it. I was on my way home from Yakima going up over white pass when I noticed my car getting super hot. After letting it cool off I was able to get some water in it and make it home. Once I got home I flushed the radiator and put in new coolant as well as a new thermostat. Well tonight on my way back to yakistan it got pretty hot going up the pass, not in the red but hotter then usual. It cooled down and seemed fine the rest of the way. When I got to my apartment, the temp gauge was reading normal but I could hear the coolant just boiling. Any thoughts of what it could be? Maybe a bad water pump or bad core in the radiator? Any replies will help, thanks!

 

Radiator cap?
That's the cheap guess...

Have you been losing coolant? Have you heard or seen evidence of water pump problems? Have you looked at the plugs? Have you seen oil in the radiator/white junk on the dipstick? Have you milkshaked it? (3.4 automatic, right?)

 

Dirt in radiator fins? Radiator plugged internally? Radiator hoses collapsing? Fan clutch not engaging properly?
Thermostat jiggle valve installed at 6 o'clock position for the 5vz-fe 3.4l engine?

Did you use a Toyota 180 deg thermostat as the replacement?