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'88 4runner overheating on freeway only(I'm puzzled)

3K views 5 replies 2 participants last post by  Rob92083 
#1 ·
I have an '88 4runner(3.0L V-6) that is having overheating issues after driving extended periods on the freeway. I just recently bought the truck from a lady who had it just sitting for about two years and have replaced the water pump, t-stat, most of the hoses, timing belt, plugs, wires, cap&rotor, and all fluids(have not yet replaced the radiator). The truck runs great other than having to turn on the heater while driving on the freeway for extended periods. Any suggestions/help would be much appreciated. Thx.
 
#3 ·
I didn't even attempt any major trips before I did the work. It was in dire need of some attention. The fluid in the radiator was like a rust colored mud. Also on top of all the other stuff, I did flush the block/radiator(several times)and now the fluid is a nice green. It's wierd it only gets hot on the freeway. The truck drives fine in four-wheel drive, with the a/c on, offroad, all day long out in the desert in one hundred degree heat. Darn thing just hates these crazy California freeways....
 
#5 ·
Rob92083,

You know it almost sounds like your thermostat is not opening all the way. That is maybe why at slow speeds it operates normally, but when on the freeway it is not open enough to allow proper cooling. I would take it out and put it on the stove and heat some water and watch to see if it opens all the way. I bet it is bad and is not uncommon for this to happen with a new t-stat. I have seen may new ones fail right out of the box. I would look into that before you do anything else.
 
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