hey lankchevy... i took both heater lines off of the engine. one from the intake and the one from the water pump, then i put the nozzle of my garden hose and forced water thru it. allot of brown ditry crappy water came out. i kept running water till clean water came out. hooked everything back up and now i have heat. i have heard of people blowing compressed air thru it then using water, but i just decided to do the water thing.