Interior and Upholstery 89 Foxbody heater core replacement problems.

jrichker

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Mar 10, 2000
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I have watched the various videos and even followed the tech note here on Stangnet on heater core replacement, but I still have a problem.

I have removed all of the known and obvious items like the A/C accumulator mount and both sets of nuts that hold the heater box in place. I have sufficient room between the dash and the heater box. However, it seems that there is some screw or bolt in the transmission tunnel area that still needs to be removed.
The heater box has dropped down several inches and the plumbing and heater box mount studs are on the passenger side of the firewall. At that point I should be able to move the heater box towards the rear of the car enough to get to the 2 back screws on the heater core cover. But I can't get it back far enough to do that. It seems that there is a hidden bolt somewhere; I just can't move the heater box where it needs to be.


I do know that there are some small changes in the body sheet metal for year to year so I am looking for input from 87-89 Mustangs. If any of you had a similar experiences, please contribute your solution to the problem.
 
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In the general area where I am pointing.
 
@Mstng93SSP I appreciate your willingness to help, but the 89's heater case is very different from the one shown in the picture. There is no bolt in that area.

Indeed, there are some small changes in the body sheet metal for year to year and this is one of them.
 
Not sure I know what is holding yours, but I just changed the heater core in my 89 without pulling the box. I left the AC hooked up and was able to pry open the heater core cover enough to remove and replace the core. I think I had all the bolts loose, but the drivers end of the box did not move much. The ac connections kept the pass end of the box from moving a lot also.

There may be a wire harness bracket on the drivers end somewhere.
 
@Mstng93SSP
Your tip about the 3rd bolt was a winner: ) You were right, thanks again for your help.

I had to jack the heater box up to see the mystery 3rd bolt, but sure enough it was there. I removed the passenger seat and was able to get a straight shot at it. When the bolt came out, I could pull the heater case out and replace the bad heater core.
 
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The heater core was by far the most pain in the butt thing I have done to my stang in eleven years I have her.
 
Newbie question on this topic...the heater core on my ‘86 started leaking today after my first good run with my newly updated 5.0. Knowing what’s a pain the replacement is, does it make sense to replace the A/C coil at the same time?
 
I remember this. LoL You could get the same thing on an 86 if ordered correctly. Of course, nobody knew this was a "thing" back then :shrug:
I think the dealer had to add the AC to sell a black car (with palomino/ pumpkin interior) in Nebraska. I was very glad they had with as hot as it got half of the year.