1976 Cadillac ‘short cut’ heater core replacement 😁

[V63]

1976 Eldorado needed heater core replaced. Did NOT want to go conventional 16 hour nightmare route. Went With The 90 minute route.
(NOTE: NOT found anywhere in the FSM) 🤦🏻‍♂️


1. Cut and remove firewall sheet metal enough to extract core from engine compartment (create a trap door)

2. Cut and remove rubber sheeting and cellulose insulation to expose heater core.

3. Remove 1 sheet metal screw holding core (between hose connections)

4. Pull core out thru trap door opening.

5. I used 'exploding foam' to line inside of trap door to replace removed insulation.

Whole process about 90 minutes. ☺️

Will update completed job after I image and install 'trap door',

[The Tassie Devil(le)]

Sure makes it look easy.

Don't know why Cadillac didn't design it that way.

Bruce.

[Cadillacdave]

I have considered doing the repair the very same way and everyone advises against it. Personally, I think it is a great idea. How much wider were the cuts to the firewall, than the actual size of the heater core, to make the trap door? 1/2 inch bigger than the heater core? Thank you

[dennisspeaks]

This is great and i will sleep better, I had been praying not to have to do this the conventional way.  It's a no brainer in my book I don't see why everyone advises against it?

[Big Fins]

Somehow, I just can't see myself butchering the box to save a few hours of work.

To each their own.

[Cadillacdave]

I would agree that no one wants a " butchered" job. From the looks of your finished pictures it looks nice and neat and is not " "butchered" at all. If done skillfully in the manner you did it - it looks great! Also, removing a dash to do this job is expensive and it usually never goes back exactly as it came out. There are usually some missing bolts or tabs and then you are stuck with a squeeze or rattle.

We have all seen hack jobs that folks do to cars but this is not it. Obviously, you were careful with the cuts and fit the trap door back where it is barely noticeable. A little sealant and paint and it looks like it was made that way. Great job! Thanks for sharing with us.

[James Landi]

Back in the "Olden days," on some American cars, the heater core was  easily accessed through a metal panel  on the fire wall.  I do vividly recall that my 56 developed a leak inthe core on passenger side, and peed on a colleague shin. those two cores were in the kick panels on either side of the front seat.

[Big Fins]

That's a '56, James. Years behind the '76, which is a different world.

[jagbuxx #12944]

I replaced the heater core on my 75 Fleetwood (now sold) and it wasn't that bad of a job. There are some posts that helped and the FSM of course-except there are 5 bolts to remove, not 4.
My estimate is that it took me about 7-8 hours over 3 days. I would never think of cutting thru the firewall. Sorry, my 2  cents

[wrench]

On one of my cars, I would do that in a heart beat.

I am definitely a 'better mousetrap' mechanic.

And it's not very hard to build a better mousetrap than GM

I would do the access cover and insulation differently.

[James Landi]

"I am definitely a 'better mousetrap' mechanic."

I'm with you Jim...  If I can figure out a suitable "work-around" I'm on it; however, with the more modern computer controlled Cadillacs, the work around usually involves  bungee cords!  James