any of you guys run across a heating issue with 4.6 l f150s? mines a 97 4x4 been rebuilt, new thermostat,checked the blend door for operation,ok, upper rad. hose hot one heater hose hot one cold. the heat works when parked and running the engine at a higher rpm than idle. thinking water pump or heater core restriction?

 

There is a thread here with a picture of a water pump with the impeller almost completely rusted away. Not circulating water. That said, it is a one in a thousand. You probably have a clogged heater core. Try reverse flushing the crud back out the back way. If it clears your good for a while. Dont let the crud get back to the radiator. Not so good. If you have one of those black mixing pans now is the time to put it under the truck to catch the spill. If you have new coolant you can filter it into a bucket with a towel to get the dirt out of it. Sometimes a little air pressure is necessary to break up the clog on the core. Just be careful not to burst it. It's good for 30 psi no problem.

 

thank you for the input. it was a clogged heater core thats what i ended up checking friday i just wasnt thrilled about trying to get to the heater hoses

 

It's a messy business but someone has to do it and you didn't pay a bunch. If it happens again you may need a new core. Not fun to change. good luck