Help! Replaced heater core & control valve, now overheating | Ford Explorer Forums - Serious Explorations

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Help! Replaced heater core & control valve, now overheating


New Member
September 10, 2003
Reaction score
City, State
atlanta, ga
Year, Model & Trim Level
2000 XLT
Let me start this by saying I'm a fairly newbie mechanic so please be gentle. Alright, here goes...

My wife drives a 94 x. A few days ago she started noticing a strange smelling smoke coming through her ac vents. Having used this forum for research in the past, I looked here and found the post describing how to replace the heater core on first gen explorers. It sounded like this was my problem so I replaced it. In the process of trying to replace it, I accidently broke off one of the hose connections on the heater control valve and had to replace that valve as well.

After replacing the valve and the core, I put everything back together and cranked it up. No smoke came out so I thought it was fixed but when I tried to run the heat it only blew cold air and never heated up. Also, after running for a few minutes, it started to overheat very quickly and I had to shut it off. I thought maybe I put the heater control valve in incorrectly but after looking at it again, it looked right. Also both hoses running out of the valve to the heater core were very hot to the touch so I thought that meant the valve was working correctly. I know overheating like this is usually a sign of the t-stat being faulty but I'm not sure thats it because the car ran fine (other than the stinky smoke when the heat was on) before I replaced the core and valve.

Does anyone have any idea what might be going on? Any help would be greatly appreciated as my wife is giving me a lot of grief for trying to fix it myself and it not working :)

Thanks in advance!

i dont know for sure... but try just flushing your radiator, maybe some junk from the old heater core got into the new one

You either have junk in it or air. Go out and take the radiator cap off. Turn the heater on, and crank it. You should be able to see air bubbles coming up in the coolant. Let it idle for a while but keep an eye on the temps and dont let it overheat.

I flushed my radiator and added new coolant and everything is working fine now. Thanks a lot guys!