[Print Dad]

Hello All,
Once again the old girl is having an issue.
The windshield has started to fog. This to me indicates a heater core
problem.

In researching the task I come across 2 very different solutions.

1. - Some books and people say the core is easy and just pull the glove-box, pad and radio and the box will come out

The second - books and people say, remove all the above plus the steering wheel, instrument cluster and all the dash componenets.

It seems as though this is a lot of work on a non-air car.

So I would like to hear from any people that have done this task or know about it.

The car: - 70 Mach1 - 352c - No Air

Thanks as always..... Print Dad

[alan_scott]

I swapped out a heater core on a 1970 (non A/C) a long time ago (20 years or so) and I don't remember the details, but, I DID NOT remove the steering wheel / dash to do it. I don't remember pulling the entire heater box either, I think I just split it open and left the other half bolted to the firewall.

[429ragtop]

Can you smell any antifreeze?

[Print Dad]

Hello All,
A little more info. The windshield started to frost up and when I put the defroster on it got worse. i was not too far from home, so we wiped the window and drove the car home. the windshield seemed oily I am not 100% certain it is the core but I think it is. I purchased a core and gasket set just in case.

I am attaching a picture that shows the gasket set.

I have not attempted to do anything yet. The only thing i have done is a little research,

When you look at the diagram it looks like 2 boxes combined into one.
Looks like box A and Box B. It almost looks like the bolts from the fan motor "C" go thru the box A and attach in box B. It doesn't show in the diagram but it looks like box B is held by little spring clips.

If that was the case, does anyone think it would be possible to just take the face off of box B and there is the core?

I don't really know what gasket 6 goes around. I imagine it is part of the vent system.

I would appreciate if people could look at the diagram and see what they think.

My plan was to remove both boxes as 1 unit. I believe it is held in place by 5 bolts from the firewall side in the engine compartment. The I think there is 1 bolt under the dash. This is of course in addition to the cables etc.

also I don't really understand the little box that has gaskets 1,2,3,4. This looks like a vent system but is it sitting inside box B?

Any advice is greatly appreciated.

Final thought... perhaps the boxes need to be pulled to get access to the spring clips that hold the case "B" together.

I sure could use some help form someone who has done this recently.

THanks........ Print Dad

[Print Dad]

Originally Posted by alan_scott

I swapped out a heater core on a 1970 (non A/C) a long time ago (20 years or so) and I don't remember the details, but, I DID NOT remove the steering wheel / dash to do it. I don't remember pulling the entire heater box either, I think I just split it open and left the other half bolted to the firewall.

Hello,
Could you please look at the attached pix and see if it seems at all familliar.

Boy it would be great to just have to split the outer case. I don't know if this is possible. That would save me a lot of work.
Perhaps the picture will jog the memory.. I hope so/

Thanks... print Dad

[Print Dad]

Originally Posted by 429ragtop

Can you smell any antifreeze?

Hello 429ragtop,
No I couldn't smell the antifreeze but once you hit 55+ the senses start to go.

I also looked under the heater box on the pass side and did not see any anti-freeze.
I have not had to add to the radiator.

one other odd thing I should mention....the first time I put on the defroster little "junk" came out onto the dash pad. It looked like rust particles.
Not really sue what it was, but a quick wipe of the pad and it was gone.

The defroster had not been turned on in over 25 years so i didn't pay much attention to it.

Thanks as always........ Print Dad

[sav_syn_sptz]

its probably got a small leak mines done this twice mine was hooked up wrong which causeed to leak. taking the heater core out is not fun at all had to remove glove box and remove the dash pad and some the right side of the dash i have to do mine again in the next few days

[alan_scott]

Originally Posted by Print Dad

Hello,
Could you please look at the attached pix and see if it seems at all familliar.

Boy it would be great to just have to split the outer case. I don't know if this is possible. That would save me a lot of work.
Perhaps the picture will jog the memory.. I hope so/

Thanks... print Dad

I wish I could be of more help, but, I've slept since then

I think maybe I actually did unbolt it from the firewall but couldn't get it out from under the dash. I split the case and swapped the core while it was down at an angle.

I remember thinking at the time that it wasn't as tough as I thought it would be. Too bad I don't know anyone with a 69/70 so I could take a look.

[Jay H 237]

Printdad, here's a link to my website showing the rebuild of the heater box and core replacement of the one on my 68, the boxes are similar heater_core_replacement

I'll resay this too, disconnect BOTH heater hoses at the MOTOR, route the lower one from the firewall into a container and blow compressed air into the upper one. The problem is both heater hoses terminate INSIDE the car on the heater core! This will save you from getting an antifreeze mess inside the car when removing the heaterbox/core.

Since the dashes are different and the 69 being more to it you may have to remove the dash pad along with the glove box, but that should be it. No need to remove the steering wheel, gauges, radio or anything else.

The heater box should be secured with one screw/bolt inside the car located above the passenger fresh air door. The four nuts sorrounding the heater motor on the firewall engine compartment side are what holds it in place too.


When you have everything apart see if there's oil ports on your heater motor and put some "3 in 1" or sewing machine oil in there, NOT motor oil that has detergents in it. You just want a thin non detergent oil for it. It may not have oil ports if it's original, then it's just a sealed unit, some aftermarket replacements do. If it's the sealed unit and sounds good I'd just leave it be then.

[Print Dad]

Hello Jay H 237 and others,
First Thanks for all the tips and ideas.
Jay H 237 Thanks for the great link. It makes me think this will not be that bad.

I purchased the core and a gasket set from MU and am pretty set to go.

For right now, I bypassed the core just to keep running. I blew out the core as advised.

This may not be as bad as some suggested.

I thank all the people that submitted ideas, comments and suggestions.

Thanks and i will update when I install. Print Dad

[70notop]

Yo, PrintPops,

I have a 1970 (not mach 1) and I had the heater core out through the glove box hole with little effort. My issue was all the foam gaskets inside the heater box were wore out. I tried and succeded to split the box while still in the car, but what a pain. Once I decided to pull the heater box out, soooo much easier.

Good Luck.

[Print Dad]

Hello 70notop,
Thanks...I feel pretty sure I can handle this.
Mrs. P.Dad is getting cold so i better get moving on it.

Thanks to all. I will post when I succeed. LOL

The old cold Print Dad