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Discussion Starter #1
I will be installing A/C in my '66 coupe that is a non A/C car. I thought that I would go ahead before that and remove the heater box to put new seals, clean up, etc. before covering it up with the Evaporator.

In reading instructions and looking at my heater box, I've got a couple of questions on the attached photos.

First, are the hoses correct? I believe that they were replacements and not original factory.

Second, is that some factory sealer around the portion of the unit that protrudes into the engine compartment and how do I properly dislodge it? and what is it so I can put it back they it's suppose to go. (Well 3 questions I guess)
 

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That's undercoating. It could have been put on by the dealer when sold new or any time after that. Just use a putty knife or what ever to clean it up enough to remove. Yes those are replacement hoses. Install new ones with the heater box. They should be replaced periodically.

I'd suggest while you have everything apart do yourself a favor and service the fan motor. You will need a Allen wrench set to remove the fan. On the other end IIRC a 11/32 socket to remove the end Bell on the motor. Don't worry nothing is going to pop out. It's just a shell held on by the two nuts. Oil both ends of the motor bearings. It makes a difference.
 

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In addition to @Huskinhano 's good advice (as normal), I'd suggest replacing the heater core unless that's been done recently. Nothing worse that ruining a perfectly good carpet because the core decided it was finished with this life. Also check on the heater and cowl seals and replace them if you deem it necessary. It's such a pain to drop that heater box that basic restoration is a good idea anytime you do it. It's not fancy and it doesn't show, but the peace of mind having done that work is worth it in my opinion.


As for your questions: completely agree that the hoses should just be replaced. I'm a little suspect of that substance on the firewall. It does look like undercoating, but it's not evenly coating the firewall. I'm wondering if that was laid down to cover something up. Once again I agree with Tom that you should scrape it off. I'm hoping a previous owner used it to seal the heater and hoses (which isn't a good way to do that, but whatever). If you get down to bare metal make sure you treat the metal with new primer / paint so it doesn't rust.
 

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Best heater box rebuild kit is the one made by Daniel Carpenter Reproductions and is available from NPD and some other suppliers. Use quality Motorcraft, Gates, or Dayco hoses for frequently driven cars and maybe the original type ribbed, or white or yellow stripe reproduction hose for the restored ride. Use top quality worm type stainless band clamps for the inside hose application and clock them so they could be removed easily from underneath if needed in the future without having to take the whole box out.
 

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Recommend you remove the glove box prior to the heater. It’s the best way to get to the hard to reach top mount on the heater box.
 

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Unless your plan is to install an oem style under dash A/C system the heater box will get removed and replaced with new stuff. Just one guys opinion here but unless the original look of the factory A/C is important to you, I feel the more modern underdash A/C systems are far better.
 

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That's undercoating. It could have been put on by the dealer when sold new or any time after that. Just use a putty knife or what ever to clean it up enough to remove. Yes those are replacement hoses.


agree on the hoses. but that is factory applied sealer not undercoating. all cars received a healthy dose on the firewall. some more than others. all items protruding thru firewall were supposed to get sealed. undercoating is a product applied at the dealer or aftermarket level usually on the underside only. spray can 3M can be used for replacement.
 

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The Original Undercoating breaks/cracks easily....You just have to push on it....

"First, are the hoses correct?"

No they are not. Not even close.

Correctly, ALL "Factory" A/C equipped Mustangs 1964.5 thru 1968 had either One hose Black with a White Stripe, and the other hose was Black with a Yellow Stripe.....Or Both 2 Hoses were Black with Yellow Stripes. You'd have to check Year, Plant and time Period for correctness on the colors.


ALL NON-A/C cars from 1964.5 thru 1968 had both hoses Black with White Stripes.

To buy the correct hoses, You can buy them from Kevin Marti's website "Marti Autoworks", or you can buy them thru NPD which also carries them as well. While you are there buying the hoses, Buy the correct WITTEK Factory correct hose clamps as well. They sell them in kits. Both Marti and NPD carry those as well.

:eek:)

Tony K.
 

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When I rebuilt my heater box I took out the passenger seat. The extra room to work was a godsend. Also if you desire, when buttoning up the installation, put some black 3M strip caulk around the heater hoses where they enter the firewall to seal it up. This was done at the factory.
 

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Don't forget to reach up into the cowl and clean out whatever pine needles or
stuff that made its way in over the years .
 

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Discussion Starter #12
Thanks to all of you for passing on some knowledge. Now I'm going to replace everything in the box as well as the heater core. But having decided all of this ahead of pulling the box, I was doing some scraping under the hood on the firewall and then some more looking. And then it hit me as I was looking at the heater hoses. They aren't hooked up and there is a hose looped. So I am assuming that the heater core definitely needs replacing as I'm assuming that it leaks.
 

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While you are there ordering a new Daniel Carpenter Heater Box "Re-Seal" Kit. Don't to forget order the Heater Box Heater Core "End Caps". Everyone always forgets them...(100 People right now are going...What End Caps?!??) and they are an essential part!! They keep your Heater core from banging around!..while you drive around!

See below:

1965-1968 without Factory A/C:

65-68 HEATER CORE FOAM END CAPS SET OF 2


1967-1968 with Factory A/C:

67-68 HEATER CORE FOAM END CAPS SET 0F 2 - USE WITH FACTORY AC


:eek:)

Tony K.
 

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"So I am assuming that the heater core definitely needs replacing as I'm assuming that it leaks. "

I'd say that's a fair assumption!

Here is a Heater Hose Routing "Flow" chart to help everyone out....so there's no confusion.....

:eek:)

Tony K.
 

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Discussion Starter #15
"So I am assuming that the heater core definitely needs replacing as I'm assuming that it leaks. "

I'd say that's a fair assumption!

Here is a Heater Hose Routing "Flow" chart to help everyone out....so there's no confusion.....

:eek:)

Tony K.
Thanks for the diagram, that helps a lot when trying to learn.
 

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Discussion Starter #16
When putting the heater box back in, do I need to put any coolant in the hoses before clamping them on. It feels like I read somewhere that it said to do that. Seems weird but you never know.
 

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I never have, just flush and fill the radiator system as normal, let all the air get out, squeeze a few hoses to move the coolant around, etc. Seems to me that you'd end up making a mess if you tried to fill the hoses before clamping them on. I fully admit I may have been doing this "wrong," but "it works for me."
 

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If you can solder, or have a source for someone who does, and aren't going to have a cow on originality:

I remove the inlet and outlet on the heater core, and put on longer ones, about 3" longer. It moves the hose clamp from between the box and the firewall, where it cannot be accessed, to inside the engine compartment. So if you have to change hoses again, you remove the hoses, and no fluid leaks into the carpeted area.

Likewise, if you have to take down the box, you undo at the firewall, plug the core, and do not have to drag 3 feet of hose into the carpeted area.

Also, with the 1965 1966, you do not have to do anything about the heater box when installing factory AC.
 

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There is a heater core available with longer in- and outlets, but these things usually need changed every 25 to 50 years. Not a huge job. When you refill everything, run the engine to operating temp with the car parked facing slightly uphill with the radiator cap off, making the fill point the highest point in the system for sure, giving the engine gentle varying revs to move the coolant throughout and any air to the fill point until you can't add any more and it isn't pushing out. Put on your cap, drive, and after it cools, check and top off if needed til the coolant is one inch below the filler neck.
 

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There is a heater core available with longer in- and outlets, but these things usually need changed every 25 to 50 years. Not a huge job. .
Which is why I don't bother with the extended tube cores. If removing the hoses or heater was a once-a-year thing, sure. I've had my 66 forty-five years, and I've had the heater out maybe twice.
 
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