Okay i have a dodge ram 1500 and the truck overheats if i leave the thermostat in if i have the thermostat out it just runs cold i have went through four thermostats and test the thermostats and they work good. I have replaced the radiator (cause someone told me to rev the engine in park and i did and it blew the radiator) also replaced the water pump. Replace the head gasket as well got the heads machined and all cause the truck got hot one time. The truck starts overheating right away after it reaches operating tempature i have also had a temp gun on the engine and it is getting hot replaced the cooling temp sending unit too. New cap on the resiovior as well. any ideas or something i miss maybe

 

You could have air in the system that is not allowing the thermostat to open. Would be my first guess if it's running cold without a t-stat and overheats with one and the t-stat is known to be good.

Burp the system and see what you get...

 

I bleed the system and all i have drained the coolant like four or five times

 

The fan clutch may have crapped out. I had one in my Dak that I thought worked ok until I replaced it. I was a world of difference.

Does it overheat when driving on the highway at a steady speed?

 

I agree with RamJamHemi, happened to my 02

 

as soon as it gets to operating tempature it just steadily overheats to the hot position cant even make it to the freeway