techrep

iTrader: (1)

Here is a real easy way to tell if the heater core is clogged...run the engine up to operating temp with heat selected in the cab...pop the hood and feel both heater core lines running into the cab through the fire wall...if both lines are hot...the core is not clogged...if only one line is hot the core is clogged...ensure heat is selected in the cab...

Brianmcg321

All you need to do a heater core flush is one of the Prestone flush kits from Walmart. $3.00.

If that doesn't do the trick it could also be your water pump. If the pump hasn't been changed it probably has what looks like a ninja star spinning on it instead of impellers.

If your heater tends to work better when your accelerating or flooring it up a hill it's the pump.

jjmcb

Thanks for all the replies. Funny this is now its working decent. I still need to do the flush and I thinks that's where I'm going to start. I'll look into the prestone coolant kit

Lisa Floyd

My son's 2004 F-150 Heritage is blowing cold when the heat is on. Thermostat is good....heater core is NOT leaking. Any idea on what it would possibly be? I assume the heater core could still be bad. Any way to check? Trying to keep the cost down for myself, this is my sons first vehicle.

white89gt

The heater core may be plugged, but the FIRST thing to do is check blend door operation. He could have a broken blend door, or a bad blend door motor.

Lisa Floyd

After digging into it further we found that the actuator motor is not working. The blend door would not move. I did a temporary fix on it until the weekend, when I have more time to actually work on it.


Thanks for the help!