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no heat while driving.

lastsvt

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99 explorer/03 svt f150
So I searched and haven't found my answer. I bought a 1999 Eddie bower explorer with a 5.0. This is my 5th explorer. I replaced the thermostat, temp sensor heater control valve. Did a full flush (which the rad fluid was nasty. I flushed the heater core. Checked the blend door/actuater. Everything works as should. My prob is I get a little heat at idle on start up (not hot) but it goes cold when I start driving. Only thing I could think of is the rad is bad or my heat control head is bad. Which I have the digital not the three knob. The heater hoses get hot but cool down after I drive. I did burp the system until I didn't see anymore air escape. Any help would be appreciated.
 


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1998Exp

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Almost certainly it's not a bad radiator (that would cause the system to be too hot, not too cold). It's not the 'control head' either, because it only controls air flow, and you are reporting a coolant flow problem (cold hoses).
What is your temperature gauge showing? If it's normal, something is clogged, possibly the heater core itself. And here is a wild guess: a not-so-honest seller (or perhaps one who did not need any heating) might have 'solved' the problem of a leaking heater core by plugging up one of the hoses or one the heater core tubes.
Incidentally, there is a second thread going on this same subject - take a look.

So I searched and haven't found my answer. I bought a 1999 Eddie bower explorer with a 5.0. This is my 5th explorer. I replaced the thermostat, temp sensor heater control valve. Did a full flush (which the rad fluid was nasty. I flushed the heater core. Checked the blend door/actuater. Everything works as should. My prob is I get a little heat at idle on start up (not hot) but it goes cold when I start driving. Only thing I could think of is the rad is bad or my heat control head is bad. Which I have the digital not the three knob. The heater hoses get hot but cool down after I drive. I did burp the system until I didn't see anymore air escape. Any help would be appreciated.
 




lastsvt

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99 explorer/03 svt f150
Control head does control how hot or cold your heat in your cab. Temp gauge reads normal. I flushed the heater core it flowed freely. Hoses get hot at idle but once I start driving and stop and check them they are warm not hot.
 




1998Exp

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The 'control head' does not affect coolant flow (except for turning off the valve at the firewall (the one that you replaced) when 'max cold' is selected. It does its job by letting some (or all) of the air go over the heater core after it was cooled by the A/C evaporator. It also controls to which vents this air goes. But you don't need to believe me -- take a look at the heating/cooling system diagram in one of the manuals.

Sorry I overlooked your statement about flushing the heater cores. However, on of the hoses going to it may still be plugged - just a guess. Good luck!

Control head does control how hot or cold your heat in your cab. Temp gauge reads normal. I flushed the heater core it flowed freely. Hoses get hot at idle but once I start driving and stop and check them they are warm not hot.
 




jremington59

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What temp thermostat did you put in? And how do you know the blend door is working?
 




lastsvt

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99 explorer/03 svt f150
Factory from dealership. I cut a hole in the box like a was gonna repair it and watched it while I switched it by the controls
 




lobo411

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Factory from dealership. I cut a hole in the box like a was gonna repair it and watched it while I switched it by the controls

You may have to remove the actuator to be absolutely sure. I always thought I just had an overactive heater because it would get incredibly hot with just a slight adjustment in the temp. It worked fine on full cold, and since I live in SoCal that's where I kept it 95% of the time. The only reason I fixed it was because it started not responding to temp adjustments about 25% of the time.

When I removed the actuator, I saw that the "D" shaft on the blend door was broken, but it was broken in a way that still allowed it to operate more or less.

I replaced the blend door, and now I can see that the door had been broken for years. Now I get a full range of temp adjustability, from full cold to 50/50 mix to full heat.
 




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