Heater Core Removal
By AMC Eagle Nest Member Jurjen
I replaced the heater core with a new one. It can be obtained from Ebay or any major supplier, prices $30 - $60.
It is wise to buy new hoses to the core, hoses are 3/4" and 5/8", and new clamps as well (the old ones cannot be re-used).
It is wise to buy some self adhesive foam rubber too. I used 3/8"x 2"and 3/4"x 3/4". No special tools required.
Under the hood (easy)
1. Remove battery negative cable.
2. No need to drain coolant, just a few drops will be lost. I had to cut off the hoses, because they were like welded to the pipes.
3. Remove the vacuum can and some cable retainers.
4. Remove the plug and three nuts from the blower motor and take it out.
5. There are two nuts holding the heater housing (plenum), remove them.
Inside: gauge package and parcel tray (easy)
6. Remove the gauge package: use the parking brake or block the wheels another way, put the shifter in "1".
Remove the four screws holding it to the floor and lift it over the shifter. If you move it to the driver's footwell there will be enough space to remove the plug (squeeze it) and vacuum hose.
7. Remove 8 bolts of the parcel tray and take it out.
Inside: trim and plenum (easy)
8. Remove the plastic trim on the right A-pillar, go easy on this one, it is brittle.
9. Remove the trim in the passenger footwell (you may need to remove the aluminum sill plate too).
10. Remove the two electrical plugs on the left side of the heater housing.
11. There is a small U-channel on the right of the heater housing, snap it open and take the cables out.
12. Remove the last bolt holding the plenum on the right of the housing, bend the support to the left, to free the heater housing
13. There are two bowden cables on the plenum, the damper door (cold - warm) on the right and the recirc door (max AC to defrost).Take the hairpins out and lift the cables upwards until released.
Inside: Release dash (easy)
I removed the instrument cluster as well, but that is not necessary, so I will do another "how to" on that.
13. Remove the screws on top of the dash under the window shield.
14. Remove the lower bolts from the dash from the door hinge posts left and right, remove the bolt from the emergency brake on the left as well.
15. Remove the plastic cover under the steering column. Release the two steering column bolts. This is necessary because the dash is clamped between the steering column and the car body. The dash is now completely free now and can be moved rearwards on the passenger side.
Inside: Remove plenum and put in a new heater core (difficult)
16. Now you will have to do all lot of wriggling to get the plenum out. Pull it rearwards to get the pipes through the firewall and pull it down on the right side to get it out. Use a rag over your carpet to catch a few drops of coolant.
17. Remove the old foam rubber from the top (this a dirty job).
18. Remove the two screws holding the heater core cover plate and take it off.
19. Fit the new core, mine was 3/8" too small on all sides, so it covered the edges with 3/8" x 2" foam rubber, for a nice snug fit.
20. Replace the cover and nuts, and cover the edges with new 3/4"x 3/4" foam rubber.
21. Use some foam rubber around the pipes as well to prevent a cold draft.
Inside: put the plenum back in (a pain in the tailgate)
21. I think this is the worst part. It has to get in the way it came out. Let some else have a look under the hood to help you with lining up the pipes with the hole in the firewall.
22. When lifting it up on the right side, there is a risk of scraping insulation material and that will fall right on top of your new heater core, insulating it very well indeed (someone on this forum suspected that critters had built a nest on his core, but I think this happened during installation of a new core).
Put everyting back in reverse order (you can relax now), some tips:
23. Put the damper cables on the way the came of, the red or white sticker indicates the position in the clamps, don't forget the hairpins.
24. When pushing the dash back, make sure that the top of the dash slots into the black anti-squeek rubber under the window shield.
25. I pre-filled the heater core from under the hood, to prevent air traps.
26. The bolts of the parcel tray to the right of the steering column can be a pain. I used some grease to "glue" them to the socket wrench.
27. Release trapped air. Start the engine and release the highest hose clamp near the heater core and pull the hose until it starts leaking. At first some bubbly coolant will come out, wait until it is a steady flow (yup, you will loose a drop again, for those with rambler mentality, use a catch pan) and put the hose and clamp back on.
Go and have a test ride and enjoy the heat, and admire the colour of the leaves dropping from the trees, this cold and windy autumn. Check the coolant level when the engine has cooled down.