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2/5/11 4:48pm - Original Message: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
Replacing my heater core since i tore out the console, then side panel, then... you know how it is.
 
I took out the three screws that hold the heater/AC assembly to the firewall- One up top, 2 below- still can't get it out.
 
Can anyone tell me what i missing?
 
I have diagrams- everything is right. It should be one top, 2 bottom.
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2/5/11 5:47pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
I've found a thread I'm reading.
http://www.corvetteforum.net/c3/juliet/heatercore/HeatCore_orig.htm
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2/5/11 6:13pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
I have AC, too.
 
Most of the articles online are for late-model '70s w/out AC., a lot easier to deal with.
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2/5/11 6:15pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
Sorry. I just realized this is in the wrong area. My bad.
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2/5/11 7:51pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
There seems to be this simple flat thing-not a bolt- holding this thing up. Not in the assembly manual, it is the round thing directly in the middle that goes into the firewall.
 
I would have thought this was just a fastener for the heater assembly, not bolted through the firewall. I checked. I have one accesible nut that can be taken off in the engine bay- I did it, it was not it.
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2/5/11 9:29pm - Reply: '71 Heater Core Replacement, not coming out...'
my7t1 Lifetime Member
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Dorr, MI - USA

Vette(s):
71 Colonnade Hardtop Coupe Torch Red with black interior originally L48 built to push around 360hp

Joined: 8/21/2002
Posts: 2580
OK, hope this helps. Behind the top stud ( I believe its the one in the pic) that holds the evaporator case to the firewall there will be a second nut. What I did is carefully pry the case back so I could get an end wrench on it. Then discard when it goes back together. I'm not sure its whats holding you up, but it did me until I found it. "T"

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2/6/11 11:49am - Reply: '71 Heater Core Replacement, not coming out...'
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

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There will be more than 1 stud going thru the firewall holding the heater/AC plenum in. There are a couple on the bottom, if memory serves. The studs going thru the firewall also hold the AC plenum on the engine side of the firewall. You may have to dig around with a screwdriver or some sort of scraper to uncover them...they may have been covered with a type of undercoating/sealant from the factory.
The stud in your pic is at the top of the A/C plenum under the hood, and it will be the easiest one to locate and get the nut off of. As Terry points out, taking the one nut off from the A/C plenum under the hood may still leave you with one holding the heater plenum to the firewall under that.
It's been years since I've been that far into one of these systems, so my memory ain't that good. Patience is a virtue here...


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2/6/11 4:02pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
There are several online "sources" dealing with C3 Heater cores- every one is not complete.
I'm going to try and change that so there's less headaches involved.
 
Namely, its heater cores with AC cars.
I have many pictures, that'll help. Just finished rebuilding the heater control box- still not back in, but at least the hard part is done.
 
Actually, the hard part ios taking it out.
 
That one top left is a stud that passes through the firewall AND is THROUGH the AC cover, Unscrew that nut, located just below the small headlight vacuum mechanism (I believe). Hardly noticeable, but it's there.
 
You'll also need to lightly push it through, back into the cabin. It'll be sort of "bound up."
 
 
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2/6/11 4:19pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
Every article or directions leave out certain things, obvious, but nonetheless, vital.
 
Vacuum hoses have to taken off before the box can be pulled from car, along with 2 RT side sensors and a light bulb bracket. Each vacuum line ios color coded, but I took the above shots to make sure they go back where they were pulled from.
 
Unbolt the cable on top (then put the bolt back in to not lose it) and gently pry off the round "pie" clip with a screwdriver under it. After it's off, pull the cable end "o"ring out, then snap back on that small piece or you'' lose it.
 
That top left stud causes almost all the problems. I ended up with two holes there. I actually had a small crack between the two holes- not a big deal, but don't start pulling and tugging, otherwise it could crack. I'm unsure if I did the damage or not, but I don't think so- the other hole was added i think from a prior heater core replacement, about 20 years ago.
 
Move the stereo/speaker wires out of the way. 
 
Also, the seal kit from Zip says it includes everything. It doesn't, at least for nmy 71. Later models, displayed in the directions, make do with different seals.
 
Not a big deal, but sorting out which goes where would have made the kit a heckuva lot user-friendly (and in my opinion, the only real customer service way to go).
 
I mistook several seals for heater core rebuild, but they were AC evaporative seals (my AC box/unit in the engine bay) is A-ok (not needed). Yes, you'll get a bunch of "extras" - extra headaches.
 
 
 
 
 
 
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2/6/11 4:29pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
On the side, trace the "Y" shaped bracket. The top screw is different (it holds and screws into the inside metal part that extends down from the top (where the heater core is).
 
After removing it (along with the bottom 2),  set aside Y bracket and rescrew them back in (to not lose 'em).
 
On top, unscrew the 4 top small screws on the metal perimeter. The whole HC assembly It should pull out. The brass coolant hoses from the heater core are secured by:
 
A formed metal plate. 1 small screw up top and bottom. And a the bracket that crimps down on the brass tubes. Every HC is slightly different, so there are variances. It wonj't re-install as perect as the old one is now (that's OK).
 
After those are out, unbolt that stud nut- why it's there I haven't a clue. It can't even be tightened all the way down- the metal is pre-formed bead that sticks up and the nut hits it, not allowing it to spin after a certain depth. I tightened it down as far as it would go.
 
Turn over the HC. There are 2 straps that hold it to the case, each with 2 small bolts. Take 'em off and the heater core can be twisted a wiggled out.
 
 
 
 
 
 
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2/6/11 4:47pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
Rebuilding the HC: Using some off the kit's rolled butyl rubber on a sheet, make a frame where the heater core will sit. When re-installing new HC, it will stick and hardly move, so be gentle. HC tubes and fins are fragile. Dry-run the straps over the HC ends and see if the holes line up. If not gently move them into place. Then re-install the hold down straps.
 
On the other side, reinstall the metal plate with the 2 screws. Between the brass tubes, install the hold down clamp. Begin tightening it down, while gently "persuading" the tubes into the . Remember, this clamp is important. You'll be tugging and putting on coolant hose and clamps, so you want some strength here.
 
Clean all surfaces with a adhesive remover. This takes longer than the disassembly! I used a generic type like goo-gone but cheaper- worked great. But you also have to re-wipe with alcohol or windex before the contact cement for the gaskets (leaves a residue).
 
I used the kit's large perimeter gasket, but take notice: it has a few different ways it can be installed (see my finger), with slightly different corners.Get the fastest contact cement available- ine took too long to set up- and I wanted to be done.
 
Not knowing any better, there's a foam piece in the middle. I cut it out, as it isn't needed. Checking back in the cabin, it looks like it would work (or not). there was Butyl rubber down the middle seam between the AC and heater core on the firewall. I'll check again, when re-installing it.
 
One it lifted back down into place, you'll notice - because of the thick new gasket- the holes are hard to find AND- most important- the side Y bracket (with that TOP bolt that secures the metal inside) is not visible.
 
All you do is slowly use the top 4 screws and, once seated, it will start to pull down and it will show through the opening. Re-install Y bracket and 3 fasteners.
 
 
 
 
 
 
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2/6/11 5:04pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
Another thing about universal kits:
 
They don't fit all the time. Let's see: there's a side gasket, that supposedly will go on. It won't fit. So I had it glued in place- then took it out. I ended up using some small pieces of the felt-like material included in the kit. This gasket is way too thick- you can't begin to slide the RT side assembly over the gasket and around the HC assembly. Maybe other years are different. My 71 won't use it.
 
Either way, the RT side assembly  has 2 front screws and one top screw holding it. Unscrew them, clean the ducts, then re-install using  I eneded up using soem felt and slits of duct tape- hey it worked. It won't rattle and I had a small crack on the seam- another reason why the gasket made the probelm worse- it would have snapped if i'd have forced it over the gasket.
 
So, using duct tape solved my crack and sealed it up nice.
 
Another thing about kits: Where are the rubber seals and flapper door to repair/refurbish/rebuild inside materials? All-incompassing kits= yeah, right.
 
Nowhere does this kit include redoing the whole assembly. There are a lot of cars out there with worse HC assememblies than mine- say sitting out in the elements/junklyards, etc.
 
Sooner or later, a TRUE rebuild kit would make sure to have everything needed.
 
That said, mine ionsides are fine, seal wise. the flappers were still soft and bumpers (so it doesn't just open and make a noise) were still present and OK. If the inside rubber guts are bad- you're outta luck and will have to make your own.
 
 
And again, here's some "extras"- not like my seal i pulled off (anmd left on the vacuum hose in the car). Afterwards, the vague diagram listed them as AC evap seal parts for the firewall. Ok. Where's the new piece for mine?
 
And, last but not least....
 
The heater tube seal. A pain to stretch-pull on (gentle, though)- which way does it face? Yes, one tube is bigger, and the gasket has a small hole and a larger hole. But the darn gasket can be flipped, you know.
 
You have to check back in the cabin of the car. In the car (shown in the pics) the gasket's curved end coincided with the left side. Now install that on the tubes correctly.
 
 
 
 
 
 
 
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2/6/11 5:08pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
Here's more pictures, in case i missed logging them.
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2/6/11 5:13pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
So, there's more to come.
 
This whole experience has me almost contemplating doing a detailed article on my blog
after, of course, this is done.
 
I know it was rushed, and the pics weren't perfect, but I feel it's my duty to pass on this info, especially for hard this was to find detailed info about AC cars.
 
Moderators... thank you for not kicking off the post from mistakenly posting in the wrong area and not in the heating/cooling section. 
 
 
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2/13/11 12:01pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
A few more things: I'm not afraid to admit when I'm wrong.
 
I screwed up the large gasket. Looking at the diagrams and Zip sheet, I thought it went in between the heater core metal box and the plastic heater housing. This gasket actually is the seal for the firewall, that's why there is a middle seam part (which I mistakenly cut out- it's the divider between the heater brass tubes/coollant hoses that go to the right side; the left is the AC box.)
 
Well, there's only seals in kit forms, so I couldn't just by a new seal. But there's a better alternative:
 
I stumbled on the AC isle at a local mart. All those foam/rubber seals for windows, well, there's the soliution. There's an exact match in a rolled up sealer, even with adhesive strip on the back. It's the exact size and width, too!
 
So I did a perimeter frame and this seal will probably be even better than the actual kit.
 
Cost: $3.00 (with lots of leftovers for other "auto" needs.
 
 
 
 
 
 
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2/13/11 3:43pm - Reply: '71 Heater Core Replacement, not coming out...'
dskopp
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Oak Creek, WI - USA

Vette(s):
1981 Great White Shark. Red Interior, 350/190hp. PS, PB (SS), A/C CC, T-Tops, Going to remain as Stock as possible. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vetts Car Club. 175,000 Original miles!!

Joined: 5/21/2008
Posts: 1956
Great Pictures ! 
DanThumbs Up

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2/13/11 11:21pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
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2/13/11 11:27pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
So the last couple pics show "restoring" the windshield /heater vent area. This one is easy; you really can't screw up. After you unscrew 3 bolts on the back, the two "swivel" vents come out.
 
Here you tear out the old seals and clean real good. New seals are shown as being too long for my '71. All you do is cut them to length. It's hard to get your fingers in there, but take your time and stick 'em in place. Bolt everything back together and the vents are definately "snugged" in there and stay put when you aim 'em.
 
Notice I didn't repray the outside. It looked decent enough. I did, however, really clean it well, including taking off the electrical switch before, obviously squirting with any cleaners.
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2/13/11 11:30pm - Reply: '71 Heater Core Replacement, not coming out...'
2nd2ja Gold Member
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Lino Lakes, MN - USA

Vette(s):
71 Coupe LS5 454 Auto

Joined: 1/8/2009
Posts: 138
Forgot to mention the vents themselves. The chrome/silver painting on them was worn off in areas leaving them an unmatched pair when viewing from the front.
 
My solution: I thought it would look fine black (under the chrome) so I got out the fine steel wool and "buffed" the chrome away, leaving it all a clean black. I think it stands out more.
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2/13/11 11:32pm - Reply: '71 Heater Core Replacement, not coming out...'
Jaws79 Lifetime Member
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Sykesville, MD - USA

Vette(s):
1979 Corvette Coupe Corvette Light Blue Midnight Blue interior Mirrored Glass T-tops

Joined: 4/27/2008
Posts: 4211
Great job, Aaron, but you made me feel even better about replacing my heater core while they were rebuilding my A/C system!
 
Barry
 
doh


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