I have an o4 dodge ram 4.7 that gets hot past the normal mark on the gauge and at one time overheated and set off the check engine light when I ran my a/c last summer. If I turn on the heater it stays past the norm mark slightly, I flushed the system and replaced the thermostat, now there is a small hex fitting by the upper radiator hose fitting on the motor, do I have to open that fitting to let any air out of the system? And if so do I do this when the motor is warm, running or cold? Any help would be appreciated thanx>:confused:

Not properly bleeding the air out of the system can cause any motor to overheat/ run hot, bleed it with the engine cold,and not running it's a 8mm allen. Fill it up until it comes out the bleeder hole, reinstall the plug, give the upper hose a few squeezes until no more air comes bubbling up, then reopen bleeder to be sure no more air is left in system.