Removed heater box from '81 C10 to replace the heater core, easier than I expected.

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pinballlarry1

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Kalispell, Montana
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Larry
Truck Year
1981
Truck Model
C10
Engine Size
250 6 cylinder
It went well and quickly. Disconnect coolant hoses. Take out the glove box and ash tray assemblies, removed the 3 control cables, one screw to the defroster Y pipe, and one 10mm head screw on the far-right interior firewall. Burned off the paint and coating from the three 1/4" studs that protrude thru the firewall near the fan motor.
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and the heater box actually fell out on its own.
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It's dusty and dirty but I did expect more debris inside, not too much:
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And here is the weeper, on the return tank end. Nothing obvious why it started, but it was wet in that area:
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Heater core is held in place by a round retainer bar near the hose connections, and a flat rectangular retainer bar on the return tank end.
Mine were rusty and dirty, but cleaned up ok:

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Since these steel pieces are in direct contact with the brass heater core, I plan to wrap them with rubber tape or put heat shink on them to prevent the dissimilar metals from direct contact.
 

pinballlarry1

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1981
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C10
Engine Size
250 6 cylinder
And the heater core has secret numbers on it, only visible when viewed from a very low angle.
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GTX63

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No comparison to pulling the heater core in a squarebody vs say a late model GM truck.
 

fast 99

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No comparison to pulling the heater core in a squarebody vs say a late model GM truck.
Exactly. Used to dislike replacing heater cores in these old vehicles. Being a line tech, working on newer models with a 6-8 hour + flat rate this old stuff is a piece of cake AC or not.

Worst one I can remember was a Nissan Maxima. Every bracket, brace, part came out by itself and lots of them. Forget which one goes back first, start over.
 

pinballlarry1

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114
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Location
Kalispell, Montana
First Name
Larry
Truck Year
1981
Truck Model
C10
Engine Size
250 6 cylinder
UPDATE: FINISHED with heater box repairs. Did not take pictures. Dodging heavy showers all day, but got it done. Reassembled with a new aluminum heater core, wife helped reinstall the assembly in the truck. Flushed, cleaned, flushed and refilled the cooling system with 5 quarts of antifreeze/coolant and 5 quarts of water. Ran for 30 minutes up to temp, no leaks found. Time will tell. Going to replace the radiator cap, this one is very difficult to remove, not sure why and not going to mess with it after skinning the knuckles.
 

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