bad cap?
 

05 dodge ram - doesnt overheat - gets slightly hotter when truck is sitting there running, but stays normal when driving. noticed the overflow tank doesnt fill up when truck is at operating temperature, stays low right where it is when the truck is cold. being 110+ here, i have to say this isnt right - any ideas?

4.7? Have you had flushed at all? There was a TSB that had something to do with a cooling fan, may be something with that. Could just be because its 110*F. Your thermostat may be sticking just a bit.

mechanical fan, changed clutch last summer - i can hear the fan kick in.

truck has cooled off some, opened radiator cap and radiator is full - squeezed both hoses, both times made coolant come out neck. level in overflow tank hasnt changed from operating temperature to cooled off

Has it done this in the past summers when it gets really hot out?

it is running a tiny bit hotter this summer - what is throwing me off is the overflow tank, stays at the bottom cold mark no matter how much i have been driving.

i am going to do the cap this morning, and hoses and thermostat sunday morning...

If the cap is not working properly, then it could cause you to have a higher than normal reading.

just picked up a thermostat, upper and lower hoses as well as a new cap. either tonight or sunday morning, going to flush it out and call it a day. not going to take any chances especially with the uber hot weather...

a hole in the overflow hose had a pin hole it would draw air into the rad without drawing antifreeze. that would not explain the tank not going up. if you open the cap when it is cold, ok at the ambient temperature in AZ, around 90, the radiator should be full. if the level is lower than the rad neck, the cap is bad or you have a leak.