North American Turbocoupe Organization

Heater Core Replacement
andrewjs18 Offline
Heater Core Replacement
For All 1985-88 Thunderbirds

Special thanks to Eric of Eric's Cool Cats and Lee, also
Pete from NATO and the NATO message board for some of the information below.



(All apologies to Lee)

Probably the number one most dreaded task that people fear on these cars is the eventual need to replace the heater core. You can almost bet that on one of the coldest days of the year, your core will die and leave you without heat. Well, I'm here to dispel some rumors---this isn't that bad of a job at all. If you've got an enclosed area in which to work, some basic tools, and a few hours, you can do this yourself very easily. The advantage is that you'll be saving hundreds of dollars doing this yourself vs. having a shop do it for you. An average heater core change is $300-500 at a shop. Now if I told you that it can be done yourself for about $60 US and a few hours of your time, wouldn't you rather do that and save the money? Alrighty then, read on.

The heater core is essentially a small radiator that is tucked inside a plastic box behind your dashboard. Its main job is to allow coolant to flow through once the thermostat has opened. This brings in heat, and then you can run your car's heating system and fan to warm up the interior. Now this means that you have coolant passing through the firewall and into that box. If you haven't noticed by now, the firewall is just a barrier between you and what goes on in the engine compartment. Antifreeze is the only liquid that's allowed (by federal law) to pass through the firewall and into the passenger cabin, since it's not flammable. By introducing coolant into the cabin there is potential for a real mess. So be warned now that this is a slimy job. Hey, you want to save money, right?

Symptoms Of Heater Core Failure

How do you know if your heater core is bad? Here are a few clues:

   Your radiator is full of fluid, the thermostat works fine, but you still have no heat.
   You find a puddle of antifreeze on the passenger side footwell inside the car.
   You smell antifreeze when you run the heater or defroster.
   You see puffs of smoke coming out of the defroster or vent ducts.
   Your windshield fogs up during or after you run the heater/defroster.

A way to double check this is to get the car warm, and touch both small hoses that go from the engine block to the heater core. If one hose is cold, the other warm, you've probably got yourself a dead core. You can always have your coolant system flushed and hope that it clears up the problem, but if it doesn't, it's core replacement time for sure.

Parts Acquisition

Now that you've determined that the heater core itself is bad, you have to get yourself a new one. And let me tell you, no matter what kind of deal you can get at the parts store, it is well worth the money to buy an original Ford heater core. It's definitely the best built core on the market, and will far outlast aftermarket ones. I've had people tell me that their store-bought core lasted a winter or two, and that's it. Sure, it's going to be cheaper...but do you really want to do this again in a few years? Just get the Ford core and don't even think about another kind. By the way, this same core was used in lots of Fox cars, including the Mustang, so if you want to shop online at Mustang parts places, feel free. Now you must get the core to match what you have now. So if you have a/c (which almost all of you do), then you have to get the core meant for a car with a/c. Expect to pay around $60 US for the new core.

In addition to the new core, you might want to pick up the hoses that go from the core to the engine block. They're relatively inexpensive and if you've never changed them, now is definitely the time to do that. And when the guy at the parts store asks, "Do you want, I mean, do you want new clamps with those hoses?", tell him, "Sure man, knock yourself out." Now you officially have all your parts. Time to tear into some stuff.

Removal Of The Old Core

Heh...yeah, this is the part where most people freak out. No matter what you've heard, you DO NOT have to remove the entire dash. Heck, most shop manuals recommend that too---horse nuggets. The dash only needs to come out far enough to get access to the heater core box. But that comes later; you have to disconnect a few things first.

Engine Compartment
I'm going to assume here that you still have the original-style R-12 refrigerant in your a/c system. If so you MUST get it recovered at an official facility that can do so. They'll can it for you to use later if you wish, or you can convert over to R-134a. DO NOT let R-12 bleed into the atmosphere! Now if you have R-134a already in there, bleed the system dry. Or if your a/c doesn't work (which I'm betting is the case for most of you out there), do nothing. The trick is to do the heater core swap within a day or two so you don't get a lot of atmosphere (and therefore moisture) in the a/c lines. That will prematurely rot out the system with rust.

You first have to remove the a/c accumulator on the firewall from inside the engine compartment. Disconnect the a/c lines going into the firewall (to Mr. Evaporator Core), then remove the bolts from the strap holding the cannister and remove the cannister. After it's off, remove the second set of large nuts underneath that strap. These are the nuts that physically hold the core box to the inside of the firewall. You'll also have to remove the rubber coolant lines going from the core to the block (you'll likely need to drain your cooling system to do that). If the core hoses are old and are giving you fits coming off the core, cut them off lengthwise with a utility knife and peel 'em off. Once you've done this much, your work outside the car is pretty much done for the time being.

Passenger Compartment
You should NOT have to remove the following:

   Instrument cluster
   Glove box (although it helps a little)
   Heater ducts
   Ash tray on non-console cars

You will have to remove this stuff though:

   Under-dash insulation (driver and passenger side)
   Kick panels (driver and passenger side)
   Console (if equipped)
   Floor shifter and bezel (if equipped)
   Console bracket (see photo here)
   System Sentry module, if equipped (see photo here)

Oh yeah, one more thing...these photos and descriptions are intended for the majority 1985-88 Cougars and Thunderbirds. They may or may not be exactly what's in your car. For example, if you have automatic temperature control (ATC) then you may have a different setup behind the dash than a non-ATC car. Therefore these pictures and descriptions obviously would be different than what's in your car. And this process may or may not be similar for 1983-84 cars. I've tried very hard to be as accurate as possible with this page, with a lot of help from others, but keep in mind that these cars can differ from one another and this isn't an exact science. If you feel that you have something to contribute that would help others, feel free to e-mail me.

Now what if I told you that there are only 7 bolts and nuts holding your dash to the cowl? Trick is knowing where they are. See Figure A for line art; read below for photos and in-depth detail. (Thanks to Frank for sharing the photos!)


Remove the speaker grilles from the dash, along with the cover in the center of the dash. You'll see one 7mm bolt under each cover; remove all of them.

Left speaker grille bolt.... cover bolt....


...right speaker grille bolt. That takes care of 3 out of 7.


Remove the kick panels (below the dash, to each side) and remove the bolt on each side holding the dash to the car.

Driver's side...


...and passenger's side. That's now 5 out of 7---not bad, eh?


The last two* will be 10mm nuts; they're usually painted blue so they're pretty easy to spot. Drop or remove the glove box and inside toward the back of the radio, there is a big metal bar that bolts to the outside of the radio metal support. Remove the nut from it and shove the bar off the stud.

*NOTE: Some car owners (especially of Turbo Coupes) have reported that they do not have this brace. If you don't see it right away, you probably don't have it---skip this step.

For #7 you'll have to remove all 4 bolts holding up the steering column. I think they're 5/8" deep well. The column will simply drop to the seat or the floor; it should be okay to let it hang there if you're not going to be long, but support it if you can.


Under the instrument cluster and back under the dash, you'll see nut #7 which should also be painted blue. Remove it, and you'll now be able to wiggle the whole dash free. You won't be able to fully remove it from the car, but you won't need to when changing the core. You just need enough space to get to the heater box. What you want to do is get the passenger side out as far as possible. Be very careful when doing this---these are old dashes and they can crack easily. Have someone hold it, or support it, before going any further.

If you find that you cannot get the dash out very far, double check to make sure all of the bolts are out. If you're sure they are, you may need to disconnect some harnesses in the passenger side kick panel area, by the computer.


The core box is on the passenger side; it's black and plastic. There are two straps on the top holding it to the cowl, and in each strap is a bolt. Remove those two bolts. Way underneath the box is another bolt, down by the transmission tunnel along the carpeting. It's tricky to see but you'll find it. Once those 3 bolts are out the box can be wiggled from the dash and dropped down. On the top of the box is 4 bolts that hold the cover on; remove all 4 and the lid, and underneath---voila!-----is the core.

NOTE: Some owners have reported that it's a little more difficult to get to the top of their box. This may be due to having the ATC system. You may end up reaching through the glove box hole, or from outside the car, to get to the bolts on top. Just be patient and you'll get them.

Now you may notice that there's another little friend hanging out in the heater box with the core. That's his buddy, Mr. A/C Evaporator Core. Most people can simply ignore him. Now if you have removed the A/C system or are going to, then this is the perfect time to remove him, but be careful: you have to cut up the top of the box to get him out, and that ruins the top. It may be possible to find a factory non-A/C lid but I wouldn't put too much faith in finding one now. I understand that Mr. Silicone is about the best way to repair that lid afterwards. But that's okay, because you're going to need Mr. Silicone anyway.


There's nothing tricky here---simply swap the old core for the new one. Now there is a weird rubbery/wire seal inside the lid of the core box that probably will fall apart when you removed the lid. It's technically a hermetic seal but it's shot after you've broken that seal. Take all of the old seal out and hit the lid with generous amounts of Mr. Silicone before you put it back on. Also, if your core has been leaking into the passenger footwell, you've probably got yourself a miniature green ocean in the bottom of the box. Clean all that stuff out and get it nice and dry.

Once you're done, you're ready for reassembly, which is--no surprise---the reverse of all the above. Don't forget to put the coolant lines on under the hood, and bolt up the rest of the a/c stuff. Fill the cooling system back up, reconnect the battery, and start the car. Immediately turn on the heater, full blast. Let the car warm up until the thermostat opens. You should then feel a ton of heat inside the vehicle...if so, you've done your job properly and can now leave that extra jacket in the house. Open up a cold one to celebrate, 'cause you deserve it!


All this probably sounds like a lot of work but it's really not. Ford tells their dealerships that they have 8 hours per car to do the change. You'll probably do it in 3-4 tops. The hard part is the a/c stuff; once you're past that it's a piece of cake. Now if you'd like to thank me, I prefer checks or money orders although hard cash works just the same. Wink

Jake8687 Offline
Junior Member
    Great Article. Thanks. Very similar to how I recently replaced the heater core on my 88 Mustang GT which of course is a Fox Body.
andrewjs18 likes this post

andrewjs18 Offline
(04-23-2019, 12:39 AM)Jake8687 Wrote: Great Article. Thanks. Very similar to how I recently replaced the heater core on my 88 Mustang GT which of course is a Fox Body.

glad it helped you out!

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