Interior and Upholstery 89 Foxbody heater core replacement problems.

jrichker · Feb 15, 2019

@SN Certified Technician

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.

Mstng93SSP · Feb 16, 2019

From inside the car, at the bottom of the heater box is a self tapping bolt, I think 10 mm. So, the two top bolts, and the one on the bottom and it should slide back.

Mstng93SSP · Feb 16, 2019

In the general area where I am pointing.

jrichker · Feb 16, 2019

@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.

Mstng93SSP · Feb 16, 2019

Is the 89 different from the 88? Mustang monthly did an article where they replaced the heater core on an 88 and they show bolts in the area I showed having to be removed.

Rcdgl · Feb 16, 2019

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.

jrichker · Feb 16, 2019

@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.

Mstng93SSP · Feb 16, 2019

Nice! Glad I could help.

nickyb · Mar 3, 2019

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.

Willybill32 · Jan 27, 2020

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?

General karthief · Jan 27, 2020

Ahh, yeah.
Just as soon as you get that monster back together and wiggled back together the ac will start leaking!

7991LXnSHO · Jan 31, 2020

Wow. My 79 5.0 LX with dealer AC had a small cover panel behind the glovebox, and the core about fell out in my lap. Too bad they had to make it difficult.

Willybill32 · Jan 31, 2020

General karthief said:
Ahh, yeah.
Just as soon as you get that monster back together and wiggled back together the ac will start leaking!

Thank you! I went ahead and ordered both. Now to work up the enthusiasm to start the dash work!

Noobz347 · Jan 31, 2020

7991LXnSHO said:
9 5.0 LX with dealer AC

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

7991LXnSHO · Feb 2, 2020

Noobz347 said:
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

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.

Interior and Upholstery 89 Foxbody heater core replacement problems.

jrichker

StangNet's favorite TOOL

Mstng93SSP

You have a nice rear end there Dave.

Mstng93SSP

You have a nice rear end there Dave.

jrichker

StangNet's favorite TOOL

Mstng93SSP

You have a nice rear end there Dave.

Rcdgl

jrichker

StangNet's favorite TOOL

Mstng93SSP

You have a nice rear end there Dave.

nickyb

I gotta say i never painted my nuts, Never Ever

Willybill32

But at least it's tight!

General karthief

wonder how much it would cost to ship you a pair

7991LXnSHO

wanna catch the space herp

Willybill32

But at least it's tight!

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

7991LXnSHO

wanna catch the space herp

Similar threads

Interior and Upholstery 89 Foxbody heater core replacement problems.

StangNet's favorite TOOL

You have a nice rear end there Dave.

You have a nice rear end there Dave.

StangNet's favorite TOOL

You have a nice rear end there Dave.

StangNet's favorite TOOL

You have a nice rear end there Dave.

I gotta say i never painted my nuts, Never Ever

But at least it's tight!

wonder how much it would cost to ship you a pair

wanna catch the space herp

But at least it's tight!

Stangnet Facilities Maint Tech... Er... Janitor

wanna catch the space herp

Similar threads

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