Heater Core Replacement (non-A/C)

[In The Ten Ring]

Congrats on getting yours back together so easily. I still have mine out and all I have left to do is clean up the control lever at the bottom of the box and paint the outside. *OH, and I need to remove the old rubber (circular) gasket and replace it, I have the new one.

I would LOVE to remove the surface rust from the metal flap inside but as it's held by a rivet, I am unsure if I can ever replace that or get it to work again, so I will just leave that surface rust there.

I removed some leaves and pine needles, not as much as some I have seen on here.

My local radiator shop found a brass heater core for me as they could not fix the old one.

[gkhashem]

Have a set of tongs or something for someone to hold the blower motor gasket in place for you if not the gasket will keep moving when you try to get the box back in.

I know I just did the job this morning. You will be glad you have someone helping you.

I had a complete gasket set. One for the blower. One for the inner box that rests between the core and the box inside. One for the firewall to the right of the blower and two small rectangular ones to seal around the inlet and outlet tubes on the outside of the box between your hoses and box. These seal the openings in the box at the two tube openings. I have never seen these on any of the photos on this board.

But they really make the finished job look nice. I got the whole truck sorted out except for my finicky speedometer cable and a small oil leak that is minor but I will track it down.

She is looking fine! And working fine now.

http://s1376.photobucket.com/user/gk...postlogin=true

[Redline novdog]

I have had a htr core sitting on the work bench for 2 yrs. I am afraid of removing the bolts on the inner fender breaking the nut clips on the inside. Then it's cut/drill/burn time.
Anyone have difficulty removing the fenderwell bolts???

[Redline novdog]

I put a screen (gutter screen) under my cowl panel a couple of days ago. Hop it helps keep debri out. Lot of good threads on screen installations on this site also.

[gkhashem]

Originally Posted by Redline novdog

I have had a htr core sitting on the work bench for 2 yrs. I am afraid of removing the bolts on the inner fender breaking the nut clips on the inside. Then it's cut/drill/burn time.
Anyone have difficulty removing the fenderwell bolts???

Well I had a very rust free truck plus the original owner smeared the front end and fenders with cosmoline. Actually no debris in the box at all. So I have a truck that lived a very pampered life.

Then I used an impact air wrench and no issues taking all the bolts out. The only big one had a large washer on it in the rear of the inner fender actually under the heater core box. Did not break one. If I did so what, put in another one. I did not see any clips???

The heads are smallish and would grind off pretty quick I would think. The rest of them very not very big nor long except that one big one.

[Redline novdog]

Originally Posted by 69GMCLonghorn

Literally just wrapping up this same job on mine. The heater started smoking even when it wasn't on. When I pulled the outer heater box, the amount of leaves and stuff that came out would boggle the mind! It was so bad, I had to pull the inner heater box as well because they were packed in there too. After it snowballing into a 3 month project, it should be back on the road within a week! I can't wait!

BTW, the snowball effect went like this: Oh look, the inner fender is out. Battery box is rotten through from acid. Time to replace. Oh look, the fuel pump and water pump are leaking... Ah WTH, let's replace them too. Might as well convert to a fan clutch while I'm at it. Hey that T-stat housing is almost corroded through; Yep, let's replace it.

I've put enough perfume on the pig for one project. Time to DRIVE the dang thing! SOON!

This is what I'm afraid of!!!! The wife won't have any of it. I already have a pig the Nova!!

[70STOVEBOLT]

George, the clips are on the fender, what the inner fender bolts thread into. They are called j-nuts. You can buy them from Napa if you break them.

[gkhashem]

OK guess I was not following the poster, in any event all bolts came out no issues.

Most likely due to a rust free truck and all the cosmoline inside the fenders.

[SonomaComa]

Originally Posted by slow-1

My heater core was leaking when I hooked it back up last week so I replaced it over the weekend.

I followed the suggestions from this forum AND the repair manual and it went pretty easy.

Dropped the inner fender for access to the bottom fasteners.



Propped up the hood and undid the passenger side hood hinge (after marking its location first). Used a block of wood to protect the fender, the hood and hinge slide forward enough to allow for easy removal of the heater box.





Removed:



If you ever wondered why leaves fly out of the ducts when you turn on the heat/defrost, its because there's 40 years of leaves in the heater box.





I only ran into one snag, the first core I got from Advance Auto was aluminum and did not fit, the ends of the core were not the same shape as the original so the bracket didn't fit.

Took it back and the parts girl called another store about 10 miles away and asked them to look up the same part number and they had one that was brass and correct. The guy at that store said he figures it had been on the shelf for 10 years or more.

I used plumbers putty to seal the box back to the firewall and I lubed the cables while I was at it (it was raining and I was outside so no pics of putting it back together)...now it will run you out of the truck.

Here is another thread with more pics: http://67-72chevytrucks.com/vboard/s...ad.php?t=69812

Hey, I like your informative post about replacing your heater core. I just purchased a 1970 GMC C-20 without A/C. The Heater Core Assembly looks just like yours. Except mine was not installed, I got all the pieces in a box when I purchased the truck. How does the Heater Core get installed into the Housing? Does the 5/8" or 3/4" inlet on the top or bottom? And which hose gets connected to the Water Pump?

[gkhashem]

Large outlet was on the top. Also there are two brackets the size of about double thickness of a wire coat hanger if I could guess. Both sides are held on by two small screws.

These brackets did not come with the heater core, I used the ones already on the truck. Just look at them to determine their orientation not too hard. So if yours are missing not sure what you do.

Also, NO need to remove or play with the hood. You are asking for trouble and is not necessary as I said with a NON AC truck, not sure about an AC truck.

[SonomaComa]

Thanks. I do not have A/C. So the larger outlet, 3/4", gets mounted at the top and that hose gets connected to the Intake Manifold and not the Water Pump?

[gkhashem]

Originally Posted by SonomaComa

Thanks. I do not have A/C. So the larger outlet, 3/4", gets mounted at the top and that hose gets connected to the Intake Manifold and not the Water Pump?

My larger hose on top goes to water pump. Smaller one to intake.

Also get a gasket set from LMC truck 24.99. Has gasket for blower motor and firewall and gasket inside against core. You did not say if you had the brackets?

[SonomaComa]

I have the Brackets. I have everything I need to install it now. It's just that the water outlet nipples from the Water Pump and the one on top of the Intake Manifold next to the Upper Radiator Hose have been changed. I am not sure if they were replaced with the correct sizes.
I though the water would flow from the top of the Heater Core out the bottom but now I am hearing it is the other way around. And does the hose coming from the top of the Intake Manifold push the water through and pull it through the Heater Core?

[gkhashem]

All I know is I put it back the way it was.

So it works.

Anyone else can chime in.

[SonomaComa]

Originally Posted by gkhashem

My larger hose on top goes to water pump. Smaller one to intake.

Also get a gasket set from LMC truck 24.99. Has gasket for blower motor and firewall and gasket inside against core. You did not say if you had the brackets?

And it works good with the large hose on top going to the water pump (the suction side) and the smaller hose on the bottom going to the intake manifold (the pressure side)? I am getting such conflicting reviews on this subject. I saw some other pictures here on this site with them mounted the other way around.

[Andy4639]

Heater hoses should be hooked up so the inlet is on bottom and outlet on top. Small hose goes to bottom bigger on top. Two reason. When you fill the truck up with water you want it to go to the core and fill it up with no air pockets. Also when the truck is running the outlet hose is bigger for expansion of the hot water.