I had my timing belt, thermostat, water pump replaced last Aug. 2002. I got called up for OEF (Op Enduring Freedom) so I left my 4Runner in AZ with my Dad. I came back last week (good to be home) and drove back to CA and the temp gauge went all the way to the right (hot hot hot). I had to turn off the a/c and run the heater full blast (outside temp was about 107). Anyway when I got near San Diego I turned the heater off and the temp stayed in the middle but went up when I climb the mountains. I searched the forum for some answers and I read that I have to let the truck "burp." What other actions can I take to solve this problem?

Check your coolant level in the radiator and the overflow container. If the overflow container is empty, chances are you don't have enough fluid in the radiator. Poor between 1-2 qts of 50/50 in the overflow container if it's empty. Add 50/50 to the radiator as needed.
Check your hoses. Make sure non of them have collapsed. If they have, your water pump has failed.
If non of your hoses are collapsed, replace your thermostat. It's possible that it might be stuck in the closed position. It's easy to replace. I composed a write-up over on YotaTech.

Have the motor running from cool when you fill the radiator and keep on it until the thermistat is open and it's filled to the brim. Then cap it and top off the overflow. This should bleed any air from the system. If this does not help, then get another thermistat (from Toyota only).

The hose collapsed a few times after they installed it so I brought it back and they said that it's been fixed. I brought it to Family Toyota yesterday ($15.00 for a gallon of red coolant) and they want $90 for visual inspection and $1300 to "look inside." I got more scared walking in the store than walking the streets of Iraq

The temp only goes up when the truck climbs. If the thermo is deadline then it should run hot all the time, right?

That has me concerned right there. If the truck ran fine before you took it in and now it overheats after they worked on it, you should make it sound like a warranty issue. Especially if they want to charge you $1,300 to "look inside" as you said. And $90 for a visual inspection...COME AWN!!! All that means is that they put it on the rack, pop the hood, look over the top of the engine, raise the truck and look under the engine. I'll bet the cost to replace the timing belt and water pump wasn't that outrageous. But now they want $1300 to fix their mistake?

If it were my truck, I'd take it to the dealer who replaced the timing belt and water pump and tell them that it overheats now. Tell them that your hose was collapsing before and that supposedly they fixed it. I'd also tell them to give me a rental. <img src="/forums/images/graemlins/kewl.gif" alt="" />
Good luck!