Need Help with 1974 Heater Core

[Paul L.]

I posted this elsewhere but I need all the help I can get!

About six weeks ago the heater core blew on my 1974 with A/C. The people here kindly directed me to a GM #19131998 replacement. I have that at hand. The core job has a reputation for being rather nasty so I have been procrastinating.

Yesterday I decided to replace a defective radio unit and old upper dash speakers. I proceeded to pull things apart but things have stalled owing to a previous owners butchering the gauge bezel to make the old stereo "fit". I have a new bezel on order. The upper dash came out and went in without cracking for which I am $369 thankful.

But in looking at matters last evening it occurred to me that I am about 50% there re the heater core. The pic shows where things stand. If my 50% is close I might as well go to 100%! I don't want te repeat this teardown again so looking for advice. From the pic what are my next steps?

[Wayne W.]

Re: Need Help with 1974 Heater Core

Yep, your almost there.

[Harmon C.]

Re: Need Help with 1974 Heater Core

Now is the time to do the heater core. Just remove the brace and the ducts. Under the hood remove the fan and the housing. It's all pretty straight forward as to what needs to be removed.

[Jim T.]

Re: Need Help with 1974 Heater Core

It has been mentioned before and my 70 has it, your 74 could very well have it as well. A bolt with no regular head, looks similiar to a rivet head will be at the upper right of the housing as looking at picture you posted. On the engine firewall side you will see a bolt with a nut on it that will have to be removed. Your heater hoses will probably be stuck to the heater core tubes and because of the accessability you might just want to cut the heater hoses and use new ones. As mentioned, you don't have much more to remove.

[Paul L.]

Re: Need Help with 1974 Heater Core

Jim,
I've had them go out before on my former 1979 with no A/C. Those came out the firewall side in one hour. This is a different animal. That core blew at a gas station about three miles from home. After a fill-up I noticed a pool of coolant under the car and the lovely green stuff on my new oxblood rugs. I yanked the rad cap to relieve pressure and made it home at 190*F so no problem. The spillage on the rug was not permanent as I hit it with cleaners immediately.

I do not have a lift but I cut the heatercore hoses at sight line on my best back prone position, given a lower back problem. Then I connected water pump to intake manifold and the car has been running well since. But of course this core matter has to be fixed.

I will contemplate my navel tomorrow as to whether I can jack up the car (with stands of course) and get those old core hoses and clamps off by crawling underneath. Unless I can do that there is no point going further on the inside. People with lifts are blessed!

[Paul L.]

Re: Need Help with 1974 Heater Core

OK, I got the remnants of the old hoses off. That was quite a treat with the clamps basically inaccessible from the angle crawling on my back and the old rubber welded to the brass spouts. So I just cut things apart with tin snips. So the old heater core is history. Bubba? Whatever, it's done.

In any case what are the next steps? This is a Technical Board and I would appreciate help!

[Jim T.]

Re: Need Help with 1974 Heater Core

Paul it has been to many years since I changed the heater core on my A/C 70, however I am wondering if you connected new heater hoses to your new core and fed the hoses down when installing the housing with the heater core attached if this would save some tedious hose clamp tightening?
Anyway remove the brace, the the housing from the interior and you can install the new heater core.

[Paul L.]

Re: Need Help with 1974 Heater Core

Thanks Jim. The deed is almost done and I will do the hose job on a friend's lift at a later date. Meanwhile I will drive with the bypass in place.

For info here I took this pic of the old Harrison unit and the new AC Delco #15-63338.




The old.



The new. It fit into the box nicely.