Heater Core Removal & Installation -- Directions
10-31-2007, 05:08 PM
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Heater Core Removal & Installation -- Directions
Heater Core Removal/Installation– Directions
Following is a detailed description of the removal of the heater core in a 1981 Corvette. The vehicle has a 4-speed transmission, A/C, 6-way electric driver’s seat, power antenna, and an AM/FM stereo radio w/cassette player. These directions are based on directions posted in this newsgroup by Dale Wilson (dalewilson99), in January 2007, which themselves were based on directions posted by Paul Shelley in September 2004. Note that the procedure may vary slightly or significantly for C3 models with different options or of different years.
Removal of the heater core is notoriously one of the worst repair efforts on C3 Corvettes. I hope this posting helps ease some of the pain. I recommend proceeding slowly and methodically. Have a good supply of baggies on hand and place all hardware from each removed component in its own well-labeled baggie. I use masking tape and a magic marker to make labels. Also, label both ends of every disassembled electrical or vacuum connection (A to A, B to B, etc.). This will insure that you use the correct fasteners at the correct locations during reassembly, properly reconnect electrical and vacuum lines, and make the whole job much easier.
1. Remove the driver side center console side panel (3 screws). Do this before you disconnect the battery or you will not be able to reach the rearmost screw (since you have to move the driver’s seat).
2. Disconnect battery ground (negative) cable. Before doing this, make sure that the driver’s seat is all the way back (for maximum working room under the dash).
3. Drain radiator.
4. Raise right front of car. Cut the two heater hoses just below the heater core pipe stubs. Remove the hose clamps. Cut away the remaining hose material attached to the heater core pipe stubs.
5. Remove the T-tops.
6. Remove the passenger seat (2 x 1/2” bolts on rear rails & 2 x 1/2” bolts on front rails).
7. Remove the passenger kick panel (1 screw).
8. Remove the glove box insert (2 screws on top, 2 on side, 2 on bottom), all inside glove box.
9. Remove passenger side center console side panels (3 screws).
10. Place some kind of drop cloth on the passenger side flooring to catch any debris (to protect your rugs and permit easier cleanup).
11. Remove the 8 screws securing the tunnel console trim plate. Two screws (2 x 1/4”) attach the front of the parking brake cover and reinforcement to the back of the trim plate. Four screws (4 x 5/16”) attach the center of the trim plate to the tunnel console. The last two screws (2 x 9/32”) attach the front of the tunnel console trim plate to bottom of the center gauge cluster assembly. For each pair of screws, one is on the driver’s side and one is on passenger’s side.
12. Run a strip or two of masking tape along the edge of the tunnel console trim plate where it meets the center gauge cluster assembly to protect it from scratches. Put a small cloth over the rest of it, too.
13. Remove the radio *****. Pull off the volume & tone controls from the left side and the tuning and fader controls from the right side.
14. Remove the two slotted nuts attaching the radio to the center gauge cluster assembly. One on the volume/tone shaft on the left side and one on the tuning/fader shaft on the right side. I used needle nosed pliers to rotate the nuts. The radio will still be supported by a reinforcement bracket on the right side of the tunnel console.
15. Remove the center gauge cluster’s attaching screws (2 screws on top, 2 screws on side).
16. Remove the screw from the reinforcement bracket on the right side of the tunnel console still holding the radio in position. Move the radio towards the front of the car to limit the amount the radio’s control shafts protrude through the center gauge cluster. Support the radio from the back with one hand as needed.
17. Gently pull the center gauge cluster towards you. Disconnect the illumination bulb’s socket (at the top of the cluster).
18. Disconnect the cluster’s electrical socket by squeezing the lock tab at each end of the socket and pulling it out of the cluster’s printed circuit. Mark the top of the socket, since it can be reinserted either way.
19. Disconnect the oil temperature’s electrical socket. Mark its orientation.
20. Remove the center gauge cluster from the dash.
21. Pull the radio towards you. Remove the antenna cable by pulling it out of its socket.
22. Disconnect the power antenna wire socket (mine used orange & brown wires).
23. Remove the three adjacent wire sockets by squeezing the lock tab on the right side of each socket and pulling it out of the radio. Note the color order of the sockets, since they can be reinserted in any sequence. Mine came out of the radio in the order of black, white, and blue, as viewed from the top of the radio to the bottom.
24. Remove the radio from the dash.
25. Remove the upper trim panel across the top of the windshield. There are 8 total screws: 4 along the rear edge of the panel and 4 along the bottom of the panel. Mark the screws appropriately, since the rear edge screws are longer than the bottom screws. This panel has to be removed because it covers the tab on the right pillar trim panel.
26. Remove the right windshield pillar trim panel (3 screws). To remove it, slide it up the pillar & pull it towards the back of the car. The electrical wires to the vanity mirror light run through this panel and the wires are glued to the inside of it. Once loose, I taped it to the windshield and the outside of the pillar with the wires still in place.
27. Remove the right side dash retaining screws (2 screws on the lower far right end of the dash, facing the door jamb). The passenger side of the dash is now loose. Do not pull it away from the base of the windshield yet. Wait until you see how much clearance you eventually need -- the less it is flexed, the better.
28. Remove the radio reinforcement bracket from the right side of the tunnel console (2 x 5/16”).
29. You are now ready to start removing ductwork. You will need to remove a total of 5 ducts. I include part numbers in case you have access to a way to see what each looks like before you start removing them. They are (in the order you will remove them):
1. Right side vent duct (round, curved tube, part # 467364)
2. Main vent distribution duct (part #14004950)
3. Lower heater deflector duct (part #??)
4. Heater-defroster distribution duct (part #463499)
5. Heater housing duct assembly (part # 3043318), your ultimate goal.
30. With the dash loose, duct #1 should drop right out onto the passenger floor with a little coaxing.
31. Remove the screw (5/16”) holding the right side of duct #2 to the left side of duct #5. Remove duct #2 through the right bottom of the dash, guiding it around the wiring harness on the left side of the dash. This is a big duct and a tight fit. Go slowly. When duct #2 is removed, the vent duct on the left side of the dash (the left side’s counterpart to duct #1) will pivot towards the floor. Just let it lie like that – it doesn’t have to be removed.
32. Remove the glove box door (4 x 9/32” screws). Upon reassembly, don’t defer this step until later. Once duct #1 is reinstalled, getting to the two screws on the left side of the door is very difficult.
33. Remove the screw (5/16”) on the left side of duct #3 attaching it to duct #4.
34. Pull/push duct #3 to the left to unclip it from the latch on the bottom of duct #4. While doing this, pull it rearward (towards you) and, when free, to the right to remove it from the dash.
35. Remove the screws (3 x 5/16”) on the left side of duct #5 attaching it to the right side of duct #4. The middle screw has a “J” bracket attached to it for hanging vacuum tubes & electrical wires.
36. Disconnect the vacuum line from duct #4 and remove duct #4 from the dash.
37. Disconnect the vacuum line from the actuator in the passenger kick panel.
38. Remove the screws (3 x 10mm) holding duct #5 to the firewall. Two of these screws are along the bottom of duct #5 and one is in the upper right corner.
39. The upper left corner of duct #5 is held to the firewall by a nut (7/16”) in the engine compartment. Use this approximate geometry to find it under the hood. It is threaded onto a rather long stud (which is itself threaded into duct #5). I used a deep socket to remove it.
40. Duct #5 is now disconnected from the firewall. You should be able to break it loose by gently starting to rock it up and down. Break it loose far enough so that it will tilt backward so that you have easy access to the heater controls.
41. Before removing the heater control mechanism, operate the TEMP control lever so you see how the control mechanism is adjusted (the heater door should *fully* close when the TEMP lever is *almost* at the COLD setting). You will have to adjust this mechanism upon reassembly.
42. Remove the screws holding the temperature control mechanism to the top of duct #5 (3 x 1/4”). Mark the position of the screws in the bracket so you can reinstall them in the same place.
43. Remove the retainer and the TEMP control cable from the heater control mechanism. Pry the retainer up the shaft gently with a screwdriver and then do the same with the cable end.
44. Move the cable away from duct #5 so it will not be in your way as you remove duct #5.
45. Pull back your drop cloth and passenger side rug for maximum under-dash clearance.
46. Break duct #5 fully loose from the firewall by rocking it up (the bottom edge back towards you) and down (the top edge back towards you). The lower right corner of my duct (where the heater core pipe stubs stick out of the firewall) was so stuck to the firewall that it felt like there was another attachment that had to be removed. It turned out that the rubber grommet had been liberally smeared with adhesive at the factory and that adhesive was still sticky and pliable after 26 years. Keep rocking it gently – it should eventually break loose.
47. Once loose, disconnect the vacuum line from the back of the duct. Don’t forget to install this vacuum line upon reassembly. Once duct #5 is back in place, it’s impossible to get to.
48. Gently guide the duct out under the bottom edge of the dash. I expected this to be a major time-consuming operation, but the duct was out in about 15 seconds. I barely had to flex the dash.
49. Remove the heater core retainer plate from the duct (1 x 1/4” screw).
50. Slide the rubber grommet off the pipe stubs.
51. Remove the back cover of the duct from the front of the duct (4 x 1/4” screws). You can locate the screws under the sponge rubber gasket by locating their outlines on the front of the duct.
52. Remove the heater core from the duct. Congratulations!
53. Reverse these steps to install the new heater core.
Here are some other suggestions from my experience doing this job:
1. To reseal the two halves of duct #5, consider using strip caulk. The part number at my local Chevy dealer was # 19023, but I’m not sure if that’s a GM number.
2. If you need to reseal very irregular surfaces (e.g., if you are also doing the evaporator housing and/or blower motor housing), 3M makes something they call Windo-Weld Ribbon Sealer. 3/8” x 15’. Part #05113508612. It also comes in 5/16” and 1/4” thicknesses.
3. Dr. Rebuild sells a nice A/C-Heater Box rebuild kit. Part #8846402.
4. Dry fit all ducts first to make sure you know how they go back together before installing new gaskets & sealers.
5. Use some kind of light adhesive to hold the duct #5-to-firewall gasket in place during reinstallation.
6. Vacuum test all actuators to make sure they are working before reassembly.
7. Replace all bulbs in the center gauge cluster assembly before reassembly.
8. Consider using a high-quality duct tape to seal ducts to each other. Especially duct #4 to the defroster duct (mine had a 3/4” space between them) and duct #2 to duct #5 (my mating surfaces were significantly deformed).
9. If you are also doing the blower motor housing, Dr. Rebuild sells a nice screen to prevent leaves and other debris from getting sucked past your blower and into the evaporator housing. Part #8846436.
Following is a detailed description of the removal of the heater core in a 1981 Corvette. The vehicle has a 4-speed transmission, A/C, 6-way electric driver’s seat, power antenna, and an AM/FM stereo radio w/cassette player. These directions are based on directions posted in this newsgroup by Dale Wilson (dalewilson99), in January 2007, which themselves were based on directions posted by Paul Shelley in September 2004. Note that the procedure may vary slightly or significantly for C3 models with different options or of different years.
Removal of the heater core is notoriously one of the worst repair efforts on C3 Corvettes. I hope this posting helps ease some of the pain. I recommend proceeding slowly and methodically. Have a good supply of baggies on hand and place all hardware from each removed component in its own well-labeled baggie. I use masking tape and a magic marker to make labels. Also, label both ends of every disassembled electrical or vacuum connection (A to A, B to B, etc.). This will insure that you use the correct fasteners at the correct locations during reassembly, properly reconnect electrical and vacuum lines, and make the whole job much easier.
1. Remove the driver side center console side panel (3 screws). Do this before you disconnect the battery or you will not be able to reach the rearmost screw (since you have to move the driver’s seat).
2. Disconnect battery ground (negative) cable. Before doing this, make sure that the driver’s seat is all the way back (for maximum working room under the dash).
3. Drain radiator.
4. Raise right front of car. Cut the two heater hoses just below the heater core pipe stubs. Remove the hose clamps. Cut away the remaining hose material attached to the heater core pipe stubs.
5. Remove the T-tops.
6. Remove the passenger seat (2 x 1/2” bolts on rear rails & 2 x 1/2” bolts on front rails).
7. Remove the passenger kick panel (1 screw).
8. Remove the glove box insert (2 screws on top, 2 on side, 2 on bottom), all inside glove box.
9. Remove passenger side center console side panels (3 screws).
10. Place some kind of drop cloth on the passenger side flooring to catch any debris (to protect your rugs and permit easier cleanup).
11. Remove the 8 screws securing the tunnel console trim plate. Two screws (2 x 1/4”) attach the front of the parking brake cover and reinforcement to the back of the trim plate. Four screws (4 x 5/16”) attach the center of the trim plate to the tunnel console. The last two screws (2 x 9/32”) attach the front of the tunnel console trim plate to bottom of the center gauge cluster assembly. For each pair of screws, one is on the driver’s side and one is on passenger’s side.
12. Run a strip or two of masking tape along the edge of the tunnel console trim plate where it meets the center gauge cluster assembly to protect it from scratches. Put a small cloth over the rest of it, too.
13. Remove the radio *****. Pull off the volume & tone controls from the left side and the tuning and fader controls from the right side.
14. Remove the two slotted nuts attaching the radio to the center gauge cluster assembly. One on the volume/tone shaft on the left side and one on the tuning/fader shaft on the right side. I used needle nosed pliers to rotate the nuts. The radio will still be supported by a reinforcement bracket on the right side of the tunnel console.
15. Remove the center gauge cluster’s attaching screws (2 screws on top, 2 screws on side).
16. Remove the screw from the reinforcement bracket on the right side of the tunnel console still holding the radio in position. Move the radio towards the front of the car to limit the amount the radio’s control shafts protrude through the center gauge cluster. Support the radio from the back with one hand as needed.
17. Gently pull the center gauge cluster towards you. Disconnect the illumination bulb’s socket (at the top of the cluster).
18. Disconnect the cluster’s electrical socket by squeezing the lock tab at each end of the socket and pulling it out of the cluster’s printed circuit. Mark the top of the socket, since it can be reinserted either way.
19. Disconnect the oil temperature’s electrical socket. Mark its orientation.
20. Remove the center gauge cluster from the dash.
21. Pull the radio towards you. Remove the antenna cable by pulling it out of its socket.
22. Disconnect the power antenna wire socket (mine used orange & brown wires).
23. Remove the three adjacent wire sockets by squeezing the lock tab on the right side of each socket and pulling it out of the radio. Note the color order of the sockets, since they can be reinserted in any sequence. Mine came out of the radio in the order of black, white, and blue, as viewed from the top of the radio to the bottom.
24. Remove the radio from the dash.
25. Remove the upper trim panel across the top of the windshield. There are 8 total screws: 4 along the rear edge of the panel and 4 along the bottom of the panel. Mark the screws appropriately, since the rear edge screws are longer than the bottom screws. This panel has to be removed because it covers the tab on the right pillar trim panel.
26. Remove the right windshield pillar trim panel (3 screws). To remove it, slide it up the pillar & pull it towards the back of the car. The electrical wires to the vanity mirror light run through this panel and the wires are glued to the inside of it. Once loose, I taped it to the windshield and the outside of the pillar with the wires still in place.
27. Remove the right side dash retaining screws (2 screws on the lower far right end of the dash, facing the door jamb). The passenger side of the dash is now loose. Do not pull it away from the base of the windshield yet. Wait until you see how much clearance you eventually need -- the less it is flexed, the better.
28. Remove the radio reinforcement bracket from the right side of the tunnel console (2 x 5/16”).
29. You are now ready to start removing ductwork. You will need to remove a total of 5 ducts. I include part numbers in case you have access to a way to see what each looks like before you start removing them. They are (in the order you will remove them):
1. Right side vent duct (round, curved tube, part # 467364)
2. Main vent distribution duct (part #14004950)
3. Lower heater deflector duct (part #??)
4. Heater-defroster distribution duct (part #463499)
5. Heater housing duct assembly (part # 3043318), your ultimate goal.
30. With the dash loose, duct #1 should drop right out onto the passenger floor with a little coaxing.
31. Remove the screw (5/16”) holding the right side of duct #2 to the left side of duct #5. Remove duct #2 through the right bottom of the dash, guiding it around the wiring harness on the left side of the dash. This is a big duct and a tight fit. Go slowly. When duct #2 is removed, the vent duct on the left side of the dash (the left side’s counterpart to duct #1) will pivot towards the floor. Just let it lie like that – it doesn’t have to be removed.
32. Remove the glove box door (4 x 9/32” screws). Upon reassembly, don’t defer this step until later. Once duct #1 is reinstalled, getting to the two screws on the left side of the door is very difficult.
33. Remove the screw (5/16”) on the left side of duct #3 attaching it to duct #4.
34. Pull/push duct #3 to the left to unclip it from the latch on the bottom of duct #4. While doing this, pull it rearward (towards you) and, when free, to the right to remove it from the dash.
35. Remove the screws (3 x 5/16”) on the left side of duct #5 attaching it to the right side of duct #4. The middle screw has a “J” bracket attached to it for hanging vacuum tubes & electrical wires.
36. Disconnect the vacuum line from duct #4 and remove duct #4 from the dash.
37. Disconnect the vacuum line from the actuator in the passenger kick panel.
38. Remove the screws (3 x 10mm) holding duct #5 to the firewall. Two of these screws are along the bottom of duct #5 and one is in the upper right corner.
39. The upper left corner of duct #5 is held to the firewall by a nut (7/16”) in the engine compartment. Use this approximate geometry to find it under the hood. It is threaded onto a rather long stud (which is itself threaded into duct #5). I used a deep socket to remove it.
40. Duct #5 is now disconnected from the firewall. You should be able to break it loose by gently starting to rock it up and down. Break it loose far enough so that it will tilt backward so that you have easy access to the heater controls.
41. Before removing the heater control mechanism, operate the TEMP control lever so you see how the control mechanism is adjusted (the heater door should *fully* close when the TEMP lever is *almost* at the COLD setting). You will have to adjust this mechanism upon reassembly.
42. Remove the screws holding the temperature control mechanism to the top of duct #5 (3 x 1/4”). Mark the position of the screws in the bracket so you can reinstall them in the same place.
43. Remove the retainer and the TEMP control cable from the heater control mechanism. Pry the retainer up the shaft gently with a screwdriver and then do the same with the cable end.
44. Move the cable away from duct #5 so it will not be in your way as you remove duct #5.
45. Pull back your drop cloth and passenger side rug for maximum under-dash clearance.
46. Break duct #5 fully loose from the firewall by rocking it up (the bottom edge back towards you) and down (the top edge back towards you). The lower right corner of my duct (where the heater core pipe stubs stick out of the firewall) was so stuck to the firewall that it felt like there was another attachment that had to be removed. It turned out that the rubber grommet had been liberally smeared with adhesive at the factory and that adhesive was still sticky and pliable after 26 years. Keep rocking it gently – it should eventually break loose.
47. Once loose, disconnect the vacuum line from the back of the duct. Don’t forget to install this vacuum line upon reassembly. Once duct #5 is back in place, it’s impossible to get to.
48. Gently guide the duct out under the bottom edge of the dash. I expected this to be a major time-consuming operation, but the duct was out in about 15 seconds. I barely had to flex the dash.
49. Remove the heater core retainer plate from the duct (1 x 1/4” screw).
50. Slide the rubber grommet off the pipe stubs.
51. Remove the back cover of the duct from the front of the duct (4 x 1/4” screws). You can locate the screws under the sponge rubber gasket by locating their outlines on the front of the duct.
52. Remove the heater core from the duct. Congratulations!
53. Reverse these steps to install the new heater core.
Here are some other suggestions from my experience doing this job:
1. To reseal the two halves of duct #5, consider using strip caulk. The part number at my local Chevy dealer was # 19023, but I’m not sure if that’s a GM number.
2. If you need to reseal very irregular surfaces (e.g., if you are also doing the evaporator housing and/or blower motor housing), 3M makes something they call Windo-Weld Ribbon Sealer. 3/8” x 15’. Part #05113508612. It also comes in 5/16” and 1/4” thicknesses.
3. Dr. Rebuild sells a nice A/C-Heater Box rebuild kit. Part #8846402.
4. Dry fit all ducts first to make sure you know how they go back together before installing new gaskets & sealers.
5. Use some kind of light adhesive to hold the duct #5-to-firewall gasket in place during reinstallation.
6. Vacuum test all actuators to make sure they are working before reassembly.
7. Replace all bulbs in the center gauge cluster assembly before reassembly.
8. Consider using a high-quality duct tape to seal ducts to each other. Especially duct #4 to the defroster duct (mine had a 3/4” space between them) and duct #2 to duct #5 (my mating surfaces were significantly deformed).
9. If you are also doing the blower motor housing, Dr. Rebuild sells a nice screen to prevent leaves and other debris from getting sucked past your blower and into the evaporator housing. Part #8846436.
10-31-2007, 07:13 PM
#2
Red Road Warrior
Member Since: Dec 2000
Location: Lansdale 19446 PA
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St. Jude Donor '10-'11, '15, '19
Great write up BB but I'd like to add a trick I used on my 76 & 78. I used a wood clamp, clamped about 8 inches from the core to block off each heater hose. That way, I didn't have to drain/refill the radiator. AF loss was at minimum.
John
John
06-29-2017, 08:18 AM
#3
Glad I found this. Some threads are timeless. It helped.
10-06-2017, 02:53 AM
#4
4th Gear
Member Since: Oct 2017
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Thanks for sharing such helpful post about heater core removal and installation. Last night I have came across an article about heating repair service Essex county NJ team, while searching about the tips on heating core removal, as I want to get my heater core replaced with the new one. I am now confused between the option whether I should try it on my own or else go with the professionals help! Can anyone suggest me what should I do?
