how do you flush a 2003 dodge ram 1500 heater core?

you need to drain the cooling system then pull both heater hoses off it and flush water through it both ways,and don't use real high pressure because you can damage the heater core in it ,you need to also flush the radiator and the block out also,flushing the heater core wont always give you back the heat it once had in it,once this is done refill it and run it and burp the system and check for any leaks,good luck on it.edit,another thing you need to do to that one is change the thermostat in it while its tore down its lot easier to do it now than to wait,good luck.
 
Dodgeman has it right.
Sometimes I like to add a coolant flush chemical (you can get it at any parts store) beforehand and run it or drive it for a while just to soften up any hardened deposits in the system, including the heater core. And then do exactly what Dodgeman said and flush the radiator with the fresh water both ways while you're at it. If you have access to compressed air it doesn't hurt to blow through the heater core when you are done but don't over pressure it or you could rupture it.
Best of Luck!
 
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