Replacing the heater core-Just the facts

[JimL65]

I need to replace the leaking heater core in my 1965 Gran Sport. I've searched all the Buick and A-body forums I know of and have found different options on how to do this. Everything from removing the hood, fender and inner fender to cutting a hole in the inner fender to just dropping the inner fender. There appears to be 5 nuts and 2 bolts that fasten on the engine side of the firewall. Do they all have to come out to remove the interior heating box which I believe contains the heater core? I need the facts please! As always any help appreciated.

[dsags]

First of all yes all those 5 nuts need to be removed to get the heater assembly away from the firewall to get to the heater core. One of the nuts is unreachable with the inner fender in place. Have found that removing all the bolts that hold the inner fender in place (including the ones down by the headlights) will all you to shift the inner fender forward far enough to get at that last nut. If the hood hinge on that side needs to be removed you can brace the hood in place without removing it. Not sure about the two bolts.

Hope that helps.

[GS66]

I think the job is worse if you have ac.

[option B9]

   Hi JimL65, dsags & Jim. On a 65 Skylark,Special without AC. The heater core is very simple. At 58 years old most of these Buicks don't have there original core which means that 5th nut that is under the inner well has already been removed and discarded by other mechanics. So just remove the 4 nuts and the cables on the inside. And make a note or take a photo of the color coded cables and where they attach. Then see if the the box can be pulled back and out. if not then follow the instructions that dsags posted to remove the 5th nut.
    On all the "A" body buicks that I have owned I have only encountered the 5th nut once and that's on my current 65 post coupe project because the Buick was sent to the scrapyard in 1970 and the second owner that rescued it from the yard (Steve Shuman) never replaced the core. I'm the 3rd owner.
   As far as the 2 bolts that you mentioned, I'm looking at the Chassis service manual and the GM parts catalog #674A group 9.000 Illustration #9 and I don't see 2 bolts. the 2 bolts may be for an AC "A" body. If you have an AC "A" body I'm sure some of the other member can assist you.
   If you want copies of the Illustrations that I have just send me a PM with your info and I will send them out to you.

       Tony...

[JimL65]

Thanks All. I always like to hear a job is simple before I tackle something I've never done before. Indeed just removing the 5 nuts, cables and plug will drop the interior heater box which contain the heater core. I also removed the glove compartment box to get at the cables easier. My 5th nut was still attached and a PITA to get at but with a little patience, a boxed end 7/16th ratcheting wrench and a long handled screwdriver to hold the ratcheting wrench in place while ratcheting I was able to coax it off without dropping the inner fender. I don't think that 5th nut will be reinstalled.

[telriv]

One of the things I've done in the past is to cut the corner off the heater box from the inside for that 5th. nut. IF done properly with a Dremel tool with the thin cutting disc it's not even noticeable once the box is re-installed.

Just my thoughts.

Tom T.

[JimL65]

Thanks Tom,  good information for the next guy looking to do the same.