‘68 Coronet 383 (originally 318) Heater Core Replacement

[DavidCoronet]

Ok guys, here’s one for you... my ‘68 Coronet has factory a/c, but when I bought it a few months ago the a/c components were not installed and the hoses to the heater core are missing, meaning no heat in the car. Now, I know I could just leave it be, but I would like to get the car back to fairly normal operating condition. I’m debating leaving the a/c out of the car, so I need to know if I can get away with installing a non a/c heater core in this car, and if so, how easy is it to replace? Do I need to remove the entire dash?? Man, I hope not...
Thanks in advance for the replies!

 

[Big Bad Dad]

The heater box will come out without taking the dash. The AC heater cores are completely different than the non AC heater cores. You might have to change the heater box. But they are not hard to take in and out.

 

[DavidCoronet]

The heater box will come out without taking the dash. The AC heater cores are completely different than the non AC heater cores. You might have to change the heater box. But they are not hard to take in and out.

I hope you are right that it isn’t that hard to do...

 

[OKDart]

As far as I know, a non A/C heater box will not fit an A/C car, the firewall is different. The non A/C heater core will not work in an A/C box either.

If you're sure the heater core is bad, and you don't plan on using the A/C, then one option is to route the heater hoses through the A/C evaporator. You will need to cut the ends off the A/C hoses and clamp the heater hoses to them. I would use junkyard hoses for this. There is more restriction in the evaporator than in the heater core, so while idling, it won't blow very warm, but will be fine at all other RPMs.

I did that for years in one of my cars until I tore it down for restoration.

 

[Richard Cranium]

I’m debating leaving the a/c out of the car, so I need to know if I can get away with installing a non a/c heater core in this car, and if so, how easy is it to replace?

Some of the fastening holes along with the heater core holes are in different locations between an a/c heater box and a standard heater box. Plus you'll have a bunch of extra holes in the firewall should you go that route.

Bottom line is that it's not a simple swap at all.

 

[DavidCoronet]

As far as I know, a non A/C heater box will not fit an A/C car, the firewall is different. The non A/C heater core will not work in an A/C box either.

If you're sure the heater core is bad, and you don't plan on using the A/C, then one option is to route the heater hoses through the A/C evaporator. You will need to cut the ends off the A/C hoses and clamp the heater hoses to them. I would use junkyard hoses for this. There is more restriction in the evaporator than in the heater core, so while idling, it won't blow very warm, but will be fine at all other RPMs.

I did that for years in one of my cars until I tore it down for restoration.

I just got the car a few months ago and am still learning it. I’m not quite sure if the heater core is bad...I just see that the previous owner removed the a/c components and I see the heater core holes are wide open with no hoses going to them. He rerouted the heater hoses to bypass the core. I’m not sure why he did it. I’d like to have heat in the car again.

 

[DavidCoronet]

Some of the fastening holes along with the heater core holes are in different locations between an a/c heater box and a standard heater box. Plus you'll have a bunch of extra holes in the firewall should you go that route.

Bottom line is that it's not a simple swap at all.

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I was afraid of that. Thanks for explaining!

 

[steve from staten island]

If you want AC id suggest Classic air. The heater AC box is all contained and its a fairly simple install. The heater/defroster works great. They sell it for non AC cars as well as far as i know.

 

[Sixpactogo]

I just got the car a few months ago and am still learning it. I’m not quite sure if the heater core is bad...I just see that the previous owner removed the a/c components and I see the heater core holes are wide open with no hoses going to them. He rerouted the heater hoses to bypass the core. I’m not sure why he did it. I’d like to have heat in the car again.

From this information, Here is what I would do.
1. take an old 5/8 garden hose and cut in half.
2. hook the cut ends on the heater core tubes.
3. hook the female hose to a water source and flush out the heater core for a while.
4. check for water dripping from the heater box.
5. If the core is not leaking and the flush water is clear, I would install new hoses between the engine and heater core.
My guess is the previous owner didn't car about the heater or the A/C and disconnected both for that reason. You don't need to remove the heater box unless your heater core leaks or you want to rebuild it. Another problem you may run into is the blower motor. It is 50 years old and probably stuck or dry. When they get dry and crusty they use a lot of current and can burn up your blower switch and or melt wires. Make sure it runs freely and moves the air as it should.

 

[moparsaver]

Sixpactogo posted the same thoughts I had. I would also let clean water run over the cowl panel (specifically the wiper pivots) and inspect for leaks under the dash from the wiper pivots. Some people mistake this leak as a heater core leaking and bypass the core.

 

[DavidCoronet]

Thanks guys, I will DEFINITELY be flushing it out (as you said) and check for leaks!

 

[DavidCoronet]

From this information, Here is what I would do.
1. take an old 5/8 garden hose and cut in half.
2. hook the cut ends on the heater core tubes.
3. hook the female hose to a water source and flush out the heater core for a while.
4. check for water dripping from the heater box.
5. If the core is not leaking and the flush water is clear, I would install new hoses between the engine and heater core.
My guess is the previous owner didn't car about the heater or the A/C and disconnected both for that reason. You don't need to remove the heater box unless your heater core leaks or you want to rebuild it. Another problem you may run into is the blower motor. It is 50 years old and probably stuck or dry. When they get dry and crusty they use a lot of current and can burn up your blower switch and or melt wires. Make sure it runs freely and moves the air as it should.

Meant to ask earlier, when I put the heater hoses back on which hose goes to which outlet? In other words, which is in and which is out? (Both on engine and core)

 

[Sixpactogo]

Meant to ask earlier, when I put the heater hoses back on which hose goes to which outlet? In other words, which is in and which is out? (Both on engine and core)

If you look at the engine where the water pump is, you can see that the water is pumped out from the front nipple. (smaller 1/2" nipple) The other 5/8" nipple is the return back to the block.
If you only want heat and will not be using the A/C you can eliminate running the water through the A/C heater valve but you will need to install some sort of water shut off or you will have heat all the time. The heater core itself really don't care which way the water flows. If you will be using the factory A/C water valve, you should hook the hose from the water pump source to the top nipple on the water valve and the bottom nipple to the heater core nipple on the right. The left nipple would then be routed back to the engine. Here is a pic of the way mine is routed although my engine has a different set-up than yours.

 

[DavidCoronet]

Can I still run the hoses through the a/c water valve even though the a/c isn’t hooked up? Or was that a stupid qyestion I just asked? I’m not
Planning on fixing/hooking up the ac at this time, so I’m wondering what to do as far as you say “water shutoff”? I’m just a minimal mechanic, so this confuses me a little bit. I appreciate your help!!

 

[DavidCoronet]

I mean, if I routed the hoses to simply go from the water pump to the core, then back to the water pump that would give me heat all the time, but would that really matter unless I turn up the fan?

 

[Billccm]

I'm not 100% certain on ac cars, but if similar to non ac cars the heater door will be closed when the temp is on cold. Therefore the heat won't enter the interior.
I'm shade tree trained mechanic wise. I recommend getting the factory service manual. There are free downloads on moparts web site, but I prefer books. EBay will have reproduction manuals.

 

[Sixpactogo]

Ok.........If you were to run the hoses directly from the engine to the heater core and back to the engine, you would have heat all the time. Even when it is 90 degrees outside. Trust me, you don't want that extra heat in the cabin even without the blower motor on. You need a shut off valve. The factory water valve is what regulates whether you get hot water or no water to the heater core. It is activated by the temp control on your dash. It is cable activated. When you push the temp knob down, you open the water valve under the hood. Pull it up and it closes the water valve.
You don't need to have the AC hooked up to run the heater but you do need to use the control valve or if the factory control valve leaks or is not in the circuit, you would need to bypass it and install a cable from your temperature control on the dash through the firewall to a shut off valve under the hood. This gets complicated because the factory AC heater box has another valve in the heater box that comes into play when the control switch is in AC mode. It shuts off the small valve in the heater box and closes a door in front of the heater core so the cold air from the AC evaporator can be routed through the AC vents. Pretty confusing but for everything to work properly, it needs to be hooked up.
If you only want to use the heater and want to be able to regulate the heat, you will need to hook up the heater hoses through the water valve and the heater core. When you back flush the system, be sure to push the temp control down all the way otherwise you will not get any water thru the valve. These water valves are 50 years old too and they can leak as well. When you back flush using your residence water, don't open the faucet all the way because it has more pressure than what the engine water pump creates.
Good luck