I have a 1977 Oldsmobile Cutlass Supreme with a 350 and with AC. I've attempted to replace my heater core a few months but gave up.

I have had the core bypassed since December of last year. I just used a 3/4 to 5/8 adapter and connected both hoses together. I think it's about time to fix it before winter hits (eh it's not bad here in California, but not having a functioning heater to defrost is a pain!)

I want to attempt this job again sometime next week but I've got some questions.
Does the radio have to be removed? Or better yet, does anything else besides the glove box, duct tubes, temperature control cables and the center AC Manifold have to be removed?(the car has bench seats and not the center console)

Is there a nut inside the blower resistor? I remember reading a forum that claims this to be true, yet I've read others that claim that the Evaporator and blower assembly have to be removed...

Is there anything else that I missed that I should know?

 

The radio doesn't need to come out, I pulled my passenger bucket seat out along with the console in my 76. You may want to take the bench seat out unless you have patience in a tight area.
The evaporator and blower do not need to be removed.
You'll have 3 bolts on the firewall that need to come out and 2 inside down by the floor to get the heater box out.
The glove box needs to be removed to take the selector cable off, a push in type washer .
Unplug the vacuum block connection from the heater box driver side, you'll see the 3 lines going to it .
I hope this helps
Eric

 

Of those two bolts from the inside of the car one of them seems to be screwed from the firewall. How do i access this screw?

 

Im doing the job rn and ive got thr box unbolted, or it should be. Where does this screw come from?




This is the area that the blower resistor covers, is it this nut per chance? If so whats the best way to remove this without taking off the ac box

 

You didn't need to remove anything from the engine bay other than the 3 bolts, and two bolts inside the car down by the floor. The vent on the floor has 3 screws, one on each side of the hump/floor and one in the center.
The first pic comes from the engine bay firewall, the second pic... none of that needed to be removed.

Eric

 

I've already got the 3 nuts on the engine bay side off. Temp control cable off. I only saw one screw on the inside and its this one

 

You should have another on the opposite side, can you pull the heater box out with where your at.

 

Its wiggling, but it doesn't want to come out yet. Something is holding it in. I've got the three bolts from the firewall, one by the tranny dipstick and the two on the upper and lower evaporator case. I've got the ac manifold (on the inside) disconnected. The defroster duct bolt is disconnected, and so is the lower outlet. Selector cable is off too.

 

Is it wiggling left to right, I think you will need to try to pry the bolt out past the firewall or push them through the firewall, I thinks thats where its hanging up on you .

 

Are you referring to the bolts that I sent a picture of?
I feared that I would have to do something about them.... I guess I have to take off half of the ac box :/

 

Can you pry the bolt out next to the one you removed or push it in from the firewall ?

 

My 76 has air as well although no longer working you don't need to remove anything from the a/c box, The heater box almost needs to be pulled straight out because the bolts going through the firewall hang up when trying to pull the heater box out. Same reinstalling its a bugger to get them back through the firewall while trying to put the box in on the angle it needs to go back up into.

 

Let me try

 

Try to push the upper 2 through the firewall as well, as far as you can I used a pin punch to push mine through.

 

I'm able to push them now i gotta use all my power lol here it goes

 

Put-r-ther its a bugger to get out if you can't push them through far enough, then keep pulling from bottom of the heater box it will come out.

 

question are these the vacuum connections?



And is this an issue?


This leads to the defroster

 

Yes, just pull the white connection off.

 

The second pic I can't visualise in my head really is that the floor vent? The defroster vent doesnt need to come out

 

The top bolts on to the defroster ducts. The manual only says to remove the bolt. But I don't trust the manual

 

I didn't need to remove the defroster ducts, is the box still getting hung up with all the bolts pushed through ?

 

Good thing your working on a 77 heater core, 73-77 cutlass are all the same for removal. Even thou you have to fight with the heater box, 68-72 heater core removals suck .

 

All but one are pushed through

And its this guy

 

Yeah I heard.. The fender lol

 

You should be able to pull the box out at this point by pulling from the bottom of the heater until it lifts from sticking to the padding. Ther is also weatherstripping above the heater box that sticks the upper vents to the heater box it may be hanging up ther as well I don't recall a screw holding it in but check

 

It's coming out!

 

make sure the upper vent on top of the box comes away, it is held with weather stripping that need to be replaced. I don't recall a screw in it.

 

Oh ya it sucks.

 

4 and a half hours on this and it's not out yet, but its 90% there. Thanks for all the help, I'll work some more tomorrow. By wednesday (at the most) it should have a functioning heater.

 

You very welcome, I hope I helped you out enough.
I hate to say it but its just as bad trying to get the heater box back in. A helper would be great to help you line up the wiggly bolt going back through the firewall. You will know the one I'm talking about.
Be sure to get it to seal good and tape any of the padding that may have pulled away with the box, if it doesn't seal it will be like a vacuum leak.
Cheers
Eric

 

I don't know, after reading this thread I think mine was very easy. Only took a couple of hours from start to finish.

 

Haha I bet they are, I can also bet that if the OP doesn't get the heater box to seal back up nice and tight to the firewall, it will only take a couple hours to get it back out and make sure the padding isn't wadded up anywhere.
Also I'm not the best at giving instruction especially since its been a few years since I done mine.

 

Got it out


Now these lines are in my way. These are a pain to take out

 

Yeah! That's what I'm talking about! I may finally finish today
Hope I can get everything in nicely

 

New issue. This cushion thing broke. I don't think it'll glue back. Will it hurt to not have this? Lol

 

Put-r-ther !!! The picture's are awesome, I have to thank-you for adding them. This will certainly help out the 73-77 Olds guys here. It seems like several guys with our year cars have joined lately.
As for the cushion stuff, I put mine back on that helps seal the tank hoses to the firewall. The new tanks on the heater core are now aluminium much stronger then the old copper so I wouldn't worry about them flexing when installing the heater hoses.
But just be gentle when installing the heater hose a little grease to help them slide on is ok.
I would just reuse the cushion stuff needle nose pliers will help pull it up to the firewall after the install.
How was your weather stripping on the upper vent when you pulled the box out?
I'm sure you must be a little bent out of shape after that job haha.

Nice job!!!
Cheers
Eric

 

The installation is a nightmare. What is the best way to install this. Any particular angle that worked for you?

 

Ohh I had to get my wife to help. You need someone at the engine bay with long needle nose pliers.
In the car you will need a bottle of Jack Daniels, a bottle from the medicine cabinet of, whatever that reads " to be taken orally 3x per day before meals".
I just give my wife the bottle to hang onto till the job is done .

The bolts that are clipped onto the box and move around you know the ones I mean.

 

Haha. I've been trying for a while now, nothing yet. All I've done is torn the padding but have not come close to getting it in position. The defroster ducts get in the way if it's not angled correctly. I feel the best way is to start with the box facing up and try to get as far back as possible then rotating it into position. Real pain. I'll have some help tomorrow. Hopefully it will be done.

 

Once you get the bolts through the firewall a bit then you need to position the duct. It will have weatherstripping on it, be sure the weatherstripping is on securely if not replace it or it will be a headache.
You can do it yourself from in the car but its a bugger to get the bolts through the firewall while trying to keep the weatherstripping from coming off the duct. Be sure to tape back any firewall insulation before trying to push the box up into place.