I just had my AC recharged. Then last week I watched in horror as the Temp gauge steadily climbed to the dreaded "red zone" while I was driving with the AC on the Long Island Expressway---with no shade in sight on a killer 100 degree heat!

I pulled over before it maxed out. I turned the engine off, popped the hood and watched the coolant reservoir boil for about half an hour. Then I got back on the freeway, did 65 mph with the AC off, and the Temp gauge remained just a hair above 230 the whole time for approx. 1.5 hours until I got home.

Now I am almost afraid to turn my AC on! My commute is 1.5 hours one way and it's the middle of summer in New York.

A diagram would be highly appreciated since yours truly is not mechanically-gifted.

Thanks!

Follow the big hose on the top of your motor from the radiator to your motor where it angles down. There will be a clamp to take the hose off, and then a couple bolts to remove the connection for that hose. Underneath is where the thermostat is. I feel your pain as my Jeep has done the same thing though it didn't hit the red area though.I suspect that's due to the 5.9s running a bit hotter than the 5.2s.While checking the thermostat, make sure your belt isn't slipping and/or cracked, and also make sure your reservoir at the back of your engine compartment on the passenger side is filled up to the required mark.

did you check fans if running ? a/c will put extra heat into radiator. when it is cold, hoses as temp increases, you should feel I think upper hose all of a sudden get hot, and temp gauge should come down a little, then you know thermostat is working. if it is, let run little longer (with ot temp going too high) to see if fans work. if you turn on a/c , fan should run automatically for condensor. also if you have clutch fan, you should not be able to spin easily. if can spin easy both ways, clutch fan most likelly bad.

Replace the T-Stat with a cooler one (180 degree instead of the 195 degree which is stock), I would also replace the Radiator Cap, noilover in the Resevoir is commonly caused by a bad radiator cap.