1st time poster, long time lurker. I have a '98 4x4 extended cab, 4.6. During the Fall I noticed the heat wasn't as warm as it should be. Took it the local mech last Thursday. He flushed core, got a lot of rust colored fluid out, changed the thermostat but no heat. Pulled the water pump and the blades were gone!! He thinks the blades caused some debris that clogged the heater core. I say great, new pump, flush the system and I'll be nice and toasty. Wrong! core still clogged. Alright I say, change the core. New core installed, flushed the system again but still getting clogged! He's now in the process of replacing the radiator and I've been without my truck for a week. Any ideas what else it could be if the radiator swap doesn't work?