I have just finished replacing my heater core the job went well. i started it to let it warm up and noticed i was getting no heat and that my reservoir was backing up with fluid. i have since drained the system again, pulled the heater core in and out hoses from the engine. i can blow air through them, and the core, so its not clogged. i am guessing that it could be that i need a new thermostat?

Any thoughts and ideas appreciated.
thanks

 

i think i found the problem.


looking a little ruff

 

that was it. everything working out just fine now.

 

Any time you do a core, hose, water pump or flush install new thermo. Prevents this exact thing. I have had situations where I went through 2 new thermos before one was good.

 

This is the link I used, hope it will help.

https://www.f150online.com/forums/hv...ht=heater+core

 

i used the same install instructions. they were a great help and written very well.
lesson learned on just going ahead and changing the thermo. thought i could shortcut it and save a few bucks. i was wrong and ended up spending a few more.
oh well. it works and smells great now, and my wife thinks she needs to bring a coat with her now

 

i found it to the only way out for the water is thru the air blending motor hole the motor on my truck was full of water i took it apart and cleaned it up works fine now.

 

I just changed my core on a 99 f150. Everything has been working fine for a couple days. Should I bother with the thermostat?

 

if it works fine, leave it!

 

I wish i could say the same. mine blows frigid air even if it is set on hot..new core, new t stat, i can hear the blend door actuator when i turn the ****.. so idk

 

I replaced my heater core and thermostat myself but I still have no heat could it be the door not opening in front of heater core?

 

I have the same problem. Changed the heater core, ran OK for 2 days, and now no heat. Blows cold air. The bottom heater hose is cold.
What was your problem and how did you fix it?