DIY heater core

[DEVILSorchard]

DIY and what not to do heater core install procedure

With winter coming its time to start thinking about fixing the leaky heater core you bypassed earlier in the summer. I made about every mistake possible so you don't have to. Your welcome. First things first the heater core is located and accessed under the hood, passenger side inside the big black box bolted to the firewall. You can follow the 5/8" and 3/4" heater hoses from the water pump on the front of the engine to where they attach to the heater core.

Difficulty:
-Fairly straightforward, some annoying parts

Time required:
About 1 - 2 hours for direct heater core replacement
expect an afternoon if you address some optional areas while your in there

Tools / supplies required:
7mm socket
8mm socket
10mm socket
11mm socket
1/4'' socket
flathead screwdriver or similar prying / scraping device
silicone sealant
drain basin
laquer thinner / paint thinner (optional)
well hopped pale ale or wine

Step 1:
Drain about half the cooling system. Its not necessary to drain the entire system just enough it wont overflow when the heater lines are disconnected. This can easily be done by loosing the drain valve on the lower passenger side of the rad. its located inside a 1.5" hole on the bottom of the rad support. This is also a good time to have a look at the rad hoses.


Step 2:
Remove the wiper arms. Lift up on the arm and slide the tab outward with a flathead screwdriver




Step 3:
Remove the Stainless Steel cowl trim along the lower edge of the windshield
4 screws 7mm (2 are in the wiper bump stops)




Step 4:
remove the rubber seal along the back side of the engine compartment. You only need to remove the half off the heater box




Step 5:
Remove the plastic screen between the firewall and the rubber seal you just removed. To do this you will need to remove the washer sprayer nozzle on the passenger side of the vehicle. Don't bother with the larger screw to remove the sprayer nozzle from the mount, you need to remove the entire mount.
4x 7mm screws (including sprayer mount)






Step 6:
Remove the passenger side mounts the Stainless Steel trim screws to. You may have to remove the JB weld looking cement stuff to get these nuts off. I used a flathead and gave it a light tap and it chipped and cracked off fairly easy.
4 nuts 11mm




Step 7:
Remove the blower fan, electrical connections and vacuum lines from the blower fan and AC in that area.
5 screws 1/4" for blower fan




Step 8:
Remove the little box thing located beside the AC canister
2 screws 1/4"




Step 9:
Remove the screws on the heater box cover. This is the entire top you've been removing parts from.
9 screws along the outside edge 8mm
2 screws in the center 1/4"
4 bolts in the firewall 10mm




DON'T MISS THESE TWO. ASK ME HOW I KNOW

 

[DEVILSorchard]

Step 10:
Remove the lid, Its siliconed on very well so take some time and remove as much as you can and cut along it the edges before you being. You will need to wiggle it off slowly to break the silicon before it will let go so the more you get off now the better.
If you don't remove all the screws you can easily mistake its for the silicone holding it together until it snaps while your pulling so take a second look if its really sticking. You will also have to guide it past the studs on the firewall the Stainless trim mounts attach to. Do not use a pry bar or you will break your windshield. Again I found that out the hard way.


This is what happens when you miss a screw Now its time for that Pale ale I told you to get with your supplies.


Step 11:
Removing the heater core when you get the lid off is as simple as removing the last bolt on the hold down bracket and slipping it out of the heaterbox. For the express install you can slip the new one in and start bolting it all back up at this point. The next few steps are optional if your in a rush or had enough at this point Skip step 12




Step 12:
You've probably found a bunch of rust after your removed the lid along the firewall. Now is a good time to take care of that before you cover it back up. I used a wire wheel on a drill to remove the loose rust, silicone and JB Weld crap (age hardened factory seam sealer). I plan to do a more in depth restoration in the near future or I probably would have put a bit more effort in than this, but this is still quite adequate.
When your satisfied with your work clean it well with the lacquer thinner and mask the area for paint. I used a sandable primer because of the quick flash time (dry within the hour), rustoleum, epoxy primer etc would be better yet.







Step 13:
Now your ready to start reassembling the heaterbox. Its been recommended to use rope caulking available at parts stores. I used silicon caulking from rona meant for a household windows this will make removing the lid extremely hard or nearly impossible if I need to do this again. I do not recommend using silicone.

You want to seal this very well, I applied a good sized bead along the mating surfaces of the heaterbox and along the firewall. Its a good idea to test fit before to get an idea where you want to apply the silicone. Before tightening it down apply some more along the firewall portion and run your finger along it to squish some between the crack. Ive been told these cars are notorious leakers in the heaterbox area and I doubt you want to do this twice.








The rest is simply following the steps in reverse to bolt it back up. My fingers are black and sticky at this point so I stopped taking picture.

 

[pontiacgp]

That is really nice of you to take the time to post a very detailed r&r of the heater core. I can member many people asking about the procedure on changing the core...

 

[81Regal]

The JB Weld crap is the factory seam sealer, likely dried out from time and head under the hood. It also looks like you are missing a part of the gasket that goes between A/C box and firewall. I would not recommend using silicone when putting the two halves back together but rather a rope calk avalible from any parts store that deals with auto body supplies.
While the box is apart its also a good time to clean out the box drain and build a silicone dam to help drain any water towards the drain rather than have it go inside on the floor.

 

[DEVILSorchard]

No problem. I've only had this car about a week and ive already used a lot of info from this site. Figured I should give some back when I can.

Thanks for adding that extra info. I'd forgot to meantion you should clean out the trap door area at the least. Mine was clogged with dirt and there was a good couple handfuls I scooped out to clear it. I had no idea the rope caulk existed, I would also habe to highly recommend not using the silicone like I did, I can garantee this isnt coming apart as easily next time I need to get in there. I will have to edit that post with this better info. Thanks

 

[nsharma]

This is an awesome post. Thank you so much.

 

[StevenKeck]

Very clear and straight forward instructions.

The only unidentified speed bump I encountered is visible in the photo accompanying Step 6. Between the thumb and index finger in the photo is a "bump stop" used to position the windshield on during installation. The bracket holding this "stop" may interfere with removal of the top of the heater box. A cut-off wheel and a Dremel tool provided the clearance