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April 25, 2006
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City, State
Dillsburg, PA
Year, Model & Trim Level
1997 XLT AWD V8
Just got done doing the blend door. YUCK! :thumbdwn: :thumbdwn: :thumbdwn: But at least I'm finished. :D :D :D

Anyway, I went ahead and changed both the blend door and the heater core...whilst I was in there. When I finished last night I had heat, and adjustable heat at that! This heat. Do I have air in the system? Would that cause it to heat erratically? I filled the coolant a bit more this morning and had heat for a moment...but it's not consistent.

Also, what's the best way to get air out of the system if that's my problem?


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no heat?

well kev lets start at the top
since you had heat after the repair sounds to me like everything was working right. do some basic stuff. open up the radiator cap while it s cold, start the truck and burp the system just to make sure all the air is out, HOW OK PARK THE TRUCK ON LEVEL GROUND TAKE OFF THE CAP AND LET THE TRUCK GET TO OPRATING TEMP WITH THE HEATER ON HIGH.
you might spill some anti freeze so be awareof that... then check the upper and lower heater hoses to make sure they re both hot!!!! ok now check the temp gauge make sure it s in normal op range, if you still have no heat try this ok it will tell you if you have a bad actuator.....
turn off the truck. open glove box to see actuator turn on truck and heater and set it to HOT< now turn off truck and remove the actuator completely gently take off the cover reconnect the wiring harness and start the truckand watch the motor in the actuator cycle the dial from cold to hot and see if it moves if it doesn t move accordingly then the actuator is bad and has to be replaced....

Check the vacuum lines for crack, and leaks. I had an intermittent actuator. It was caused by one of the plastic vacuum lines which had a crack at the vacuum piston connection.

also grab both heater hoses going to the firewall and see if they are hot(oops already been said :( ), if not you got other problems, if they are hot you got a vacuum leak or electrical problems


Ok guys....I did top off the fluid level numerous times. I did check both hoses going into and out of the heater core, and they are warm. I just checked the upper and lower radiator hoses. The upper seemed hot :D but the lower did not. :banghead:

Do I need to burp the baby some more?

Thanks again

vacuum piston

Check the vacuum lines for crack, and leaks. I had an intermittent actuator. It was caused by one of the plastic vacuum lines which had a crack at the vacuum piston connection.

Is the vacuum piston that you mentioned the thing on the line going into the heater core? How should this operate? It does seem kind of erratic. Usually the piston is extended, however one time when I started the truck it was not extended. I haven't seen much movement at all. Does the vacuum line that attaches to this control the actuator that turns the blend door?

Thanks for the tips.

vacuum piston thing

This one?

Switch to cold ac and see if the heater bypass valve moves--this is when it "closes"

Also, I have better luck "burping" the sytem when I am parked uphill, or jack the front end up--making the radiator cap higher than the heater core---
This will force "bubble" to front.


I ran it awhile with the nose up on a hill and the rad cap off.

I switched it to Max A/C the heater bypass valve does close. Then opens again when I switch off Max A/C. Does this mean the vacuum to that is fine? Strange thing though.....when I turned it back from MAX to vent, I had heat momentarily, then cold again.

:banghead: :banghead: :banghead: :banghead: :banghead: :banghead:

I think you still have air in the cooling system--keep burping it and topping it off.
The fact that you had heat momentarily leads me to believe the blend door is working--and there is an air bubble in the heater core. Remember, the heater core is the highest of all the cooling system components. Any air bubbles will quickly go there.

I have to go do some work. I'll try again this evening. I parked the X on a hill and ran it for a good half hour....twice. Still no heat.

If the problem is air...can I just drill a hole in the top of the heater core so it can escape? That would probably work just like a bleeder valve on a forced water system in a house...right?

I hope you didn't take that seriously. What would you recommend as the best way to force the air out, if it is in there?

no heat

kev i think at this point it s probably unlikely you still have air in the system,

my ford cd says to bleed the system of air all you need to do is run the heater on high with the cap off and the system will bleed when the thermostat opens. and really i doubt the heater core is gonna trap all that air where no coolant can pass through it and really if ya think about it people go to shops and the dealer for coolant flushes and i really don t think air trapped in the system on the exp is that hard to get rid of if it was a BIG PROBLEM then ford would put out a bulletin on the proper procedure like bleeding ABS systems....i think you need to look else where.

check the blend door actuator

kev i know you said you did the blend door fix but did you check to see inside the truck if the blend door actuator is working correctly inside by the glove box???? mine was creaking and making noise all i found was "BLEND DOOR FIX " on this site and unfortunatly my blend door is fine the actuator is bad. i checked my actuator by following this procedure.

1. start the truck turn the heat to hi and full hot....
2. turn off the truck, remove the actuator from behind the glove box,
i had to remove 4 screws to get mine out some just pop off..
3. remove the cover to the actuator reconnect the wiring harness to it
start the truck and with the heater on high turn the temp knob to cool and warm watch the motor.
mine was wandering and would only stay on cold,
remember theres a circuit board and motor in there that can go bad....

It sounds like i may have the same problem you are having. Two nights ago I was out of town and had heat. I had stopped for a few minute to eat, when I got back on the road and turned the heat back on all I could get was cold air.I have a clicking noise in the dash ( when I have the temp control turned to hot), sound like its coming from behind the radio area.
Does this sound like the blend door or actuator?
I have pulled apart some of the dash trying to pin point the sound, it sounds like its coming from just above the heater core. Can you get to the blend door by pulling the heater core out? I am just about ready to start pulling the ducking system out to find this clicking and to hopefully get heat

blend door actuator

GLENN read back to some of my replys
it sounds like the blend door actuator is wandering
there is a small circuit board and a motor with grears in there

AND the board or nylon gears can wearout..

I have similar problem, the only difference is I am not getting cold air. The air is slightly warm.