bottom hose stays cold,all other hoses warm,cool air from vents when at idle,hot air when driving,changed the thermostat,same result

 

Check for leaks

 

Water pump? Maybe the impeller is broken/slipping on the shaft.
I'd suspect maybe some pieces have broken off the impeller (worn bearing) and the water pump won't move sufficient water at low RPMs.

 

Is your truck over heating?????

 

no it doesn't overheat,idrove 104 miles to work and back,no problems,there are no leaks now,i just changed the intake and timing chain gaskets ,thats when i noticed the cold hose after i put it back together,i may have had this problemand just found it,i'm wondering if someone may have put stop leak in it to hide the water leaks andthe radiator is plugged up,i think it is bypassing through the heater hoses.