I noticed it yesterday sitting in the movie parking lot waiting on some people to get there with my ac on. I looked at the temp and it was over half way to hot. I cut the truck and let it sit while we watched the movie. On the way home I noticed the temp fluttered up and down but never over heated.(never much over half way)

I got home and pulled it in the shop. Under the hood I heard the sound of air and water bubbling out of somewhere. Checked all my hoses and my heater control valve was leaking some. I let it sit over night and checked my coolant levels and they are still good.

Would that leak in the valve cause the truck to run warmer? I figure it would since the system would be losing pressure when vac was applied. I'm getting a valve tonight and just want to see if thats whats causing it or is there anything else I need to get.

 

Liquids will have a higher boiling point under pressure - with a leak in your system, the coolant will boil at a lower temp. A leak could very well cause overheating.

While you're at it, you may want to check out your thermostat - for such a simple device, it can cause a lot of issues if it isn't working properly (e.g. stuck open or closed - closed would definitely end up with overheating).

FWIW, I had kind of the opposite problem last winter - the vehicle was not reaching proper operating temps and threw a code- problem was the thermostat was faulty and stuck open.

Hope you determine the problem - overheating your engine will definitely cook it (and your pocketbook) in the end.

 

I had that problem with it getting hot when i had the air on or when driving slow in fields where there wasnt much air flow. turned out to be that it was pluged upon the outside with grass, dirt, small rocks, seeds, etc. took it out and cleaned it havnt had a problem since.

 

I flushed my cooling system and replaced the valve and the truck is doing great.