Heater Core Replacement for 1968 GMC Inline 6

[68gmcdude]

Hi All...

Need to replace the heater core in my ’68 GMC with an inline 6. Anything special I need to know? Thanks...

['68OrangeSunshine]

Originally Posted by 68gmcdude

Hi All...

Need to replace the heater core in my ’68 GMC with an inline 6. Anything '' special I need to know? Thanks...

Get 2 gallons of fresh antifreeze, and 2 gallons of distilled water. Get fresh 5/8th and 3/4'' hoses. About each 3'.
Take the hoses off at the Heating Element.
Loosen the back fender screws on the Fender Skirt, and drop down if you need to get to the lowest fasteners on the plastic, or fibreglass shroud.
Look for rodent sign. Flush out if any.
Dismount heater core from plastic ducting. Check for leaks. Have a shop flush it out, or replace as necessary.
Reassemble in reverse order.

[Richard]

If you do not want to re-core your original, a copper/brass non A/C replacement can be had here https://www.classicparts.com/1967-75...tinfo/68-231C/ With A/C copper/brass https://www.classicparts.com/1967-72...tinfo/68-232C/ dimensions are provided to compare to original. The aluminum replacements do not typically fit right and do not work as well.

[72c20customcamper]

I’ve had no problems with the aluminum heater core I put in my 68 . Got it from Rockauto fit was just like the original and it throws out a good amount of heat . So much so I have to turn it down . Now I haven’t used it in 20 degree weather but I doubt I ever will YMMV

[54blackhornet]

I just love that line ! “Reassembly is the reverse of disassembly “

['68OrangeSunshine]

Originally Posted by 54blackhornet

I just love that line ! “Reassembly is the reverse of disassembly “

Straight out of the Chevrolet Service and Overhaul manuals.

[68gmcdude]

Originally Posted by '68OrangeSunshine

Get 2 gallons of fresh antifreeze, and 2 gallons of distilled water. Get fresh 5/8th and 3/4'' hoses. About each 3'.
Take the hoses off at the Heating Element.
Loosen the back fender screws on the Fender Skirt, and drop down if you need to get to the lowest fasteners on the plastic, or fibreglass shroud.
Look for rodent sign. Flush out if any.
Dismount heater core from plastic ducting. Check for leaks. Have a shop flush it out, or replace as necessary.
Reassemble in reverse order.

Thank you for this. I will hopefully be working on it this weekend...

[68gmcdude]

Originally Posted by Richard

If you do not want to re-core your original, a copper/brass non A/C replacement can be had here https://www.classicparts.com/1967-75...tinfo/68-231C/ With A/C copper/brass https://www.classicparts.com/1967-72...tinfo/68-232C/ dimensions are provided to compare to original. The aluminum replacements do not typically fit right and do not work as well.

Thanks for the link. I ordered one this morning. I had bought an aluminum one over the summer in anticipation of it going bad, but the end aren't the same.

['68OrangeSunshine]

Originally Posted by 68gmcdude

Thank you for this. I will hopefully be working on it this weekend...

One more thing. The Heater Core is held in place on the fiberglass housing by two long steel brackets, each held down by a pair of screws.
Take care where the screws go on replacement. I lost one once, and used a short drywall screw to save time. Unfortunately that sharp screw pierced the copper/brass jacket of the Heater Core and -- after seeing the leak, I was back to square one.

[68gmcdude]

Originally Posted by '68OrangeSunshine

One more thing. The Heater Core is held in place on the fiberglass housing by two long steel brackets, each held down by a pair of screws.
Take care where the screws go on replacement. I lost one once, and used a short drywall screw to save time. Unfortunately that sharp screw pierced the copper/brass jacket of the Heater Core and -- after seeing the leak, I was back to square one.

Thanks for the tip!

[yuccales]

Don't forget to undo the cable before pulling the box out. Put a dab of grease on top of the shaft to eliminate that squeaky sound.

[68gmcdude]

I'm guessing this is a stupid question, but I just want to put my mind at ease. So... I pulled the old heater core out and put the new one in, but when I went to hook up the hoses, I realized I put it in upside down from the way the original one was installed. Meaning the 5/8" and 3/4" inlet/outlet were reversed. I hooked up the hoses accordingly and everything seems ok... no leaks and I have heat. All is good, right?

UPDATE: Even though everything seems to be working ok, I'm going to pull the core back out and put it in correctly so the 3/4" fitting that runs to the the water pump is at the top, like the service manual states.