There are many posts about this problem but I have not seen mine. Only after driving several hours and if I stop for gas or shutoff the truck for a few min the temp starts climbing up.
The rad seems to be boiling and the overflow fills up. If I drive the truck with it hot it goes back to normal temps in a mile or two.
I have a new radiator, thermostat, and hoses. Any ideas?

 

Your thermostat is sticking. Cheap ones tend to do that. Get a Toyota OEM one from the delear. Then burp the system really good.

 

Why would it only stick after a long drive? I can drive in town all day and it never heats up

 

If that doesn't do the trick, and it very well should, look into getting a "sniffer" test to check for exhaust gasses in the coolant. Mine was doing the same thing and after replacing all the cheap parts like the car, and t-stat i found a leaking head gasket was my culprit. Not saying this is your problem so definately knock out the cheap stuff before you go onto the head gasket.

 

My 91 would do that and my 84 does on hot days...

My advice is to get a 3 core rad out of a V6. One out of an AT truck will work as well...

3 core and T-stat then call us back if symptoms persist.