Heater Core Write Up

[86VickyLX]

There really are none to be removed from the engine bay. Basically what those are are double sided studs. Basically tack welded to the firewall. The outer nut (engine bay) is to remove the evaporator core etc. The inside nuts are to remove the air plenum/heater core box.
I've also done a few ATC box heater cores. And honestly there isn't any difference in the procedure. just removing the cables that sit on the top for some sensors. Nothing really keeping the box in place.

[sly]

I had to remove those 2 on the engine side in my 88 because they were attached to the air plenum and not the firewall. they came out with the plenum.

[gadget73]

There is at least one on the engine bay side. I think its the lower bolt visible in Sinstral's pic. I definitely remember it being down lower than the heater core pipe level.


and yeah, other than a vacuum hose vs a cable connection, ATC and non-ATC are pretty much the same as far as getting it apart goes.

[GM_Guy]

The two bottom ones on my 89 are keyed to the plenum (double ended stud with a key in the middle. If the engine side nuts are not tight enough, you'll just spin the passenger side nut along with the stud. Once you get the plenum out you'll note the notches to align the studs, tighten them to the firewall at the correct orientation and it'll make reinstallation easier if they are already in place rather than try and fish the engine side of the studs into a couple tiny blind holes.

Sinistral, this is the only plenum pic I could find at the moment, it is a big bear, what you may also have, if this is the first time the plenum is coming out is the duct work sticking, or the duct foam seal which has deteriorated sticking the two together.

[additional pic showing the keyed studs on the '89, and mating side of plenum]

Alex.

[sinistral]

thanks, GM, that is helpful... i see two issues -- 1) so i didn't need to remove that lower nut in the engine compartment since i also removed the nut on the interior side. 2) what is that little nub for in the middle at the bottom that goes in the hole between the studs?

i can see more clearly now that the plenum really does need to be pulled straight back, esp with that nub -- i think my problem is that i've only been able to pull from the bottom, as the topside is getting hung up on the ductwork in the dash, so now it is wedged pretty good:

The two bottom ones on my 89 are keyed to the plenum (double ended stud with a key in the middle. If the engine side nuts are not tight enough, you'll just spin the passenger side nut along with the stud. Once you get the plenum out you'll note the notches to align the studs, tighten them to the firewall at the correct orientation and it'll make reinstallation easier if they are already in place rather than try and fish the engine side of the studs into a couple tiny blind holes.

Sinistral, this is the only plenum pic I could find at the moment, it is a big bear, what you may also have, if this is the first time the plenum is coming out is the duct work sticking, or the duct foam seal which has deteriorated sticking the two together.

[additional pic showing the keyed studs on the '89, and mating side of plenum]

Alex.

[sinistral]

what is this? on the firewall, next to that top stud? is it related somehow? (sorry these images are rotated, but you can see stud bottom right)



something doesn't seem "right", as i've followed the steps and got the dash out reasonably far. i can wiggle the plenum box side-to-side fairly easily, but it does not want to come forward/out -- feels like "something" is still holding it back.

[IPreferDIY]

If the problem is one of the retaining washers that I mentioned in your other thread, I'm fairly certain it was located under the plastic so that you won't actually see it. It's purpose was to make assembly easier at the factory. Find something to gently pound the problem stud(s) through the firewall without damaging the threads. If it is one of those washers, don't bother putting it back when you re-install. It served its purpose at the factory and has no other useful purpose.

[sinistral]

it feels more like it is hung up on the top, not the bottom... i was able to get the dash a bit further out. don't know if this video will work here, but you can see it appears to be pivoting left/right as i try to pull/wiggle it free.

If the problem is one of the retaining washers that I mentioned in your other thread, I'm fairly certain it was located under the plastic so that you won't actually see it. It's purpose was to make assembly easier at the factory. Find something to gently pound the problem stud(s) through the firewall without damaging the threads. If it is one of those washers, don't bother putting it back when you re-install. It served its purpose at the factory and has no other useful purpose.

[IPreferDIY]

it feels more like it is hung up on the top, not the bottom... i was able to get the dash a bit further out. don't know if this video will work here, but you can see it appears to be pivoting left/right as i try to pull/wiggle it free.

If you tried to link or embed a video, it didn't work. In any event, mine might have had only one retaining washer, and it was at the top. They just wanted something to hold it in place during the assembly process.

[VicCrownVic]

it feels more like it is hung up on the top, not the bottom... i was able to get the dash a bit further out. don't know if this video will work here, but you can see it appears to be pivoting left/right as i try to pull/wiggle it free.

I can see the animated gif, I'm on a PC not phone, results may be different on a smart phone.

Is just catching on the heater core inlet and outlet lines/pipes?
Pull the whole thing toward the seat to make sure the inlet and outlet of the heater core can clear the firewall.

[sinistral]

does that large actuator need to come off first?
also, looking at the ford HVAC manual, it says something about a temp control cable attached to plenum, but i don't see that??
i've got a pretty good view now -- something is holding it up on the upper right (but i don't think its the tubes). there's no room to see over the top of the actuator, as that section is pretty mashed up against the black firewall moulding, so i can't feel behind it.

[86VickyLX]

You forgot the bolt behind the insulation bud! Pull back the insulation and you'll see it. btdt.

[sly]

yup... what he said ^

[sinistral]

Fail

well, so much for that...

a few lessons learned: apparently there are subtle differences between these cars, but at the same time i think the sticky could be updated to clarify a few things concerning the nuts on the three studs and what gets removed from where. when you read thru it all you see conflicting reports.

in any event, i finally got the plenum out ... after breaking it. and upon further inspection, there was in fact no way it was going to come out w/o breaking it. for whatever reason, there was a nut on that upper stud between the firewall and the black plastic of the heater blower assembly under the hood. so while i did remove the nut in sly's pic (next to the heater core tubes) it was still retained behind that molded plastic.




after it broke and plenum was removed, i had to back the stud out of the nut from the interior and could see the nut then fall down between. interestingly, looking at the diagram from the shop manual, it shows a nut in this position (between plastic and firewall), but only on the one lower stud closest to fender. the upper stud (and the other lower stud) should only have the nut in the engine compartment. maybe somebody screwed up at the factory. ?

so now i've got no way to secure the top of the box upon re-installation, which of course is problematic on many levels. i was half-tempted to jerry-rig it all back together in disgust, but realized that wouldn't be so smart, as it won't seal properly especially once the lower nuts are torqued, further pulling the top of the box away from the firewall.

hopefully someone somewhere sells a replacement plenum assembly. haven't even looked yet, but any leads appreciated.

not how i wanted to spend my 3 day weekend. time to give it a break for a few days while i look for new heater box.

[sly]

BAH! that's uber annoying. If it's just the bolt mount that's broken off... you can probably cut a small metal plate and drill it to mount a bolt and secure the top of the plenum and just duck tape any holes/cracks shut.

but