Replaced heater core and now it wont blow hot air on my 2000 f150?

Answer 1

Probably the blend door. Follow the links below for more information.

The Heater core is difficult to replace on the F150 since it is buried in the plenum box. Getting to the core involves removing the steering wheel, steering column, complete dash panel, evacuating the AC, draining the radiator, and finally removing the heater box. Once you have the box out(8-12hrs), the core is simple to replace.

You want to be sure that the core is the problem before you undertake this process. If there is a strong smell of antifreeze in the cab or a puddle of coolant on the floor, the diagnosis is easy.

Check that the radiator is full, not the overflow tank, the radiator. On a cold engine you can remove the radiator cap and check the level. It should be full. If there is air in the system it will affect cab heating and engine cooling.

Another good check is to feel the two heater hoses going into the firewall from a cold start. The hoses should warm up at about the same rate and get uncomfortably hot-close to radiator temperature.

If the core appears to be OK, the next concern is with the blend door that diverts air through the heater core. This is a common failure on the F150. We have a video posted on our web site that shows how to diagnose and repair the system. Please follow my user name back to my bio page to find a cut-and-paste link to the web site. You are only a few clicks away from solving the problems.