Heater Core - this what I have to do?

[BobRitts]

1972 K10 LWB w/AC. So my heater core finally gave up the magic steam and has been poisoning me all day... It's been real cold so I had the heater on for a while, and I think I've got a quart of antifreeze in my lungs now. Dripping on the floor too...

From the looks of it I have to:
1) pull the box from the inside, half dozen 3/8 or 7/16 sheet metal screws and maybe some little pins or something, so I can get to the core itself.
2) pull the entire heater box and fan housing from the engine bay, including probably taking out the inner fender well, so I can get to the hoses that attach to the I/O of the core
3) put it all back together.

Is this the right way to replace the core? Man that looks like a lot of work... and my garage is about 0.5 degrees warmer than the outside air.

Thanks in advance!

[stllookn]

Yes...done mine twice this winter...DON"T ASK! The inner fender must come loose (not off) to remove the box and subsequently the core. I found it helps to just remove the right front wheel...lots easier to work on the inner fender that way.

[FarmTruk]

FYI...Jewels did a FAQ on this, with pics. I found it very helpful...

linky----> http://67-72chevytrucks.com/vboard/s...ad.php?t=69812

Best 'o luck. Sux getting AF all in the truck.

[JimKshortstep4x4]

With a factory AC most of the heater core replacement is inside as the core is inside the heater box. (The hoses have to be removed from the oustside of course). With the heater box removed it is pretty simple to replace the core.

Jim

[FarmTruk]

Originally Posted by FarmTruk

FYI...Jewels did a FAQ on this, with pics. I found it very helpful...

linky----> http://67-72chevytrucks.com/vboard/s...ad.php?t=69812

Best 'o luck. Sux getting AF all in the truck.

OOOOPS...didn't catch the "w/AC" part of the equation. My bad.

[BobRitts]

Originally Posted by FarmTruk

OOOOPS...didn't catch the "w/AC" part of the equation. My bad.

No worries - Jewel's post was great too, always good to see what it looks like when taken apart. Appreciate the reply!

[dwaite72lnghrn]

Ac system pull the 2 hoses off in the engine compartment. I found it easier to drop the inner fender passenger side. remove the 4 bolts that are in the engine compartment that hold the inside core box. inside disconnect the hoses for the vents and disconnect the cables to the blower relay and the resistor on the. you will find 2 hex head screws inside holding the box. remove them and the box can be gently pried off the fire wall. Just make sure you get an AC heater core.

[BobRitts]

Huge thanks to all, Especially Dave w/ the A/C pictures. That makes it much easier.

I looped it off last night and will drive it today in the cold... gonna need a haircut so the wool cap doesn't give me hat-head and make me look like a bum when I get to work.

BTW - is there a good repair manual people recommend? I've got the assembly manual from Brothers which is okay for repairs if you can find the right page.

[timcos]

So Bob...with the A/C...is it all done form the inside...except disconnecting the heater hoses in the engine compartment?

I fear this is in my very near future. I smell radiator fluid every once in a while. Also...get lots of heat at higher RPMs...a whole lot less heat to blowing cool air at idle.

[dwaite72lnghrn]

There are 4 bolts that have to be taken off in the engine compartment thats why I drop the inner fender because the time wasted with an box wrench trying to get it undone. It is quicker to loosen the 10-12 bolts on the inner and drop it to get at the bottom bolt behind it. With a air ratchet it is done in 5 minutes or less.

[timcos]

OK...I dropped the fender...Which 4 bolts in the engine bay?

I had top grind off three of the bolt heads around the circumference of the wheel well

Anyone have a pic

[dwaite72lnghrn]

You will see 4 sheet metal nuts on the engine side of the firewall. If you look in the 3rd picture you will see the studs on the heater box. At the bottom of the heater box right below the core you see a large irregular spot that is where the 4th stud was (had to epoxy it back on the first time I took it off). You should be able to see them. Like I said they are sheet metal washer type nuts.
edit: before you put the fender back on besure to use never-seize on the bolts to keep them from rusting back together.

[timcos]

Ahh..that is what I thought...but sometimes I get removal happy...and get myself in trouble.

Thanks,

Tim

[timcos]

I need a source of J-Nuts for ther inner fender to fernder attachments.

LMC does not have them (or the order person could not find them). Les at GMC Pauls is out of them for a week or two.

Can I get them locally...do auto parts stores stock these?

I need 14 of them.

[john]

I found them at NAPA. They also have the right kind of bolt.

[timcos]

Thanks John...I will be by a NAPA tomorrow.

[timcos]

NAPA

Tap Screw P/N 665-1989 Bag of 5 @ 4.99/bag
J-Nut Accessory P/N 665-1052 Bag of 7 for 4.99/bag

The J-Nut is a little bit longer but that is OK and it will take up room of which there is plenty.

When I put this back together...is Never Seize OK here? Will it not vibrate apart?

Tim

[timcos]

This went decently smooth...lots of time as I figure it out but smooth nonetheless.

I have run into a little problem.

The two screws do not want to seem to hold that hold the directional heater/ac vents control...the army green thing that connects to the heater core housing that is controled by the middle slider on the a/c controller.

Do I get bigger screws...fill the holes with something and drill smaller...and rethread the screws...or what?

Thanks.

[timcos]

ttt

[dwaite72lnghrn]

I would not go with bigger screws as they have a tendency to break out the plastic ears. Not sure what would be best, RTV(black silicone) screw and clamp till set, or epoxy the hole full and retap when dry.

[timcos]

Here is a pic of the inside of mine. and yes the bottom opf the pile of leaves (of which I was tempted to get a running start and dive head first) was soaked with green fluid...anti-freeze.

[KAILUAZ]

Tag for future reference.

[timcos]

I will add my steps here for anyone who wants them. These are for AC cabs

1. Disconnect Battery
2. Disconnect Heater Hoses
3. Drop Passenger Inner Fender

a. 7 bolts around wheel well circumference (from wheel well side)

i. You will mosy likely break a few J-Nuts...depending on how frozen
they are. (If you do...grind the head of the bolt off and buy some
more)

b. One big bolt on the rear inward section of the inner fender (from
underneath)

c. Three bolts on the upper inside and upper forward on the inner fender
(connects to fender(2) and batter tray(1))

d. Three bolts on the very forward section of the inner fender

e. Shake it loose and get it out of the way.

4. Remove the 4 nuts holding the heater core housing from the outside

a. one nut is right below the heather hose connections

b. one nut is on the driver side of the a/c housing ...essentially on the
opposite side of the condenser housing toward the driver

c. The last two are on the bottom of the a/c condenser housing on either
side of the housing

5. Go inside the cab

a. Remove the glove box door and the glovebox (makes it easier)

b. Move out of the way the ventilation system (green directional air box,
s-tube and the floor/defroster control box) (I took mine apart as I was
replacing anything that was broke...and wanted to clean the whole
thing up) - pretty easy...some obvious plugs and screws

c. Disconnect that resistor plug and take it out of the housing with its
grommet (I WD-40'd mine and it was very easy to slip back in)

d. Remove bolts at 11 and 5 o'clock (looking forward)

e. Pull the heater core housing gently away from the firewall. You do not want to break one of the bolts off that are molded into the heater core housing...that would suck and mean more work...you are also pulling the hose connections to the heater core through the firewall

f. Remove the heater core bracket(two brackets) screws (two screws per bracket) and the connection clamp (for the two heather hose connections

Reassemble in reverse order.

Of course I took out my ball valves and hoses as I replaced all the hoses, blanked off the driver side of the dash a/c outlet and cleaned it all up and installed new foam and added a couple 1/4-20 nuts to hold the dash vent in.

[timcos]

So if I squeeze a little epoxy in those holes...then drill them out (shank width of screw) will not the epoxy be too hard and as I am screwing the screws in...crack the housing as there is no give.....

Or is there give in epoxy?

[dwaite72lnghrn]

I used a self tapping screw in epoxy and didn't have a problem.