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Heater Core R&R (1972 Coupe)

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Larry Langley

Guest
1/18/2005

Well, it finally happened after 33 years of life. The heater core sprung a leak.

Decided to remove and replace it myself and will keep you all posted as to the trials and tribulations.

1. Placed the car on jack stands.
2. Removed negative lead from battery.
3. Drained the radiator.
4. Removed the heater hoses from under the car and the engine.
Those were the easy steps - now for the hard ones.
5. Removed both seats.
6 Removed ebrake console.
7. Removed shifter console.
8. Loosened instrument cluster bezel.
9. Removed passenger sill plate.
10. Removed passenger lower dash panel and disconnected right speaker wire.
11. Removed passenger kick panel and disconnected vacuum hose from vent door actuator.
12. Removed passenger carpet. (Otherwise you will spill more coolant on it).
13. Pushed instrument cluster and radio to left of center for access to ductwork while being extremely careful not to damage or kink oil pressure line.
14. Removed and tagged vacuum hoses from ducting actuators.
Things are really looking like a mess now
15. Removed defroster ducting.
16. Removed three screws attaching the center air distribution box to heater
box.
17. Removed the three inside screws holding the heater box to the firewall.
18. Removed one nut from the stud attached to the top left of the heater box protruding through the firewall. (The nut is the only external item to remove with the exception of the heater hoses).
The stud also has a wiring holder attached to it on the engine side and is easy to locate. It is just under and to the left of the windshield wiper door actuator viewed as if sitting in the car. It will be to the right and under the actuator viewed from the engine bay.
19. Push the center air distribution box slightly toward the drivers side in order to disengage it from the heater box.
20. Carefully and deliberately pull heater box toward you while rotating it about 45 degrees to the right. Rotation to the right is necessary in order for coolant entry/exit tubes of the heater core protruding outside of the firewall to clear the entrance of the firewall opening.
21. Now tag and disconnect the remaining vacuum hoses.
Things are really looking scary now!
22. Remove the Bowden cable from the heater box connecting mechanism only being careful not to bend it.
23. You should now be able to remove the heater box which contains the heater core from the car to your workbench.
24 Remove air distribution box and remaining ductwork from dash area for cleaning and resealing.

Of course at this point it appears as if the interior of the car has been worked over by a chop shop and looks rather intimidating. But, I am now ready to disassemble the heater box for removal of the heater core.
I ordered my new core from Corvette Central as well as new heater hoses and gasket set. The old gaskets and seals in the heater box and ductwork were very deteriorated. At this point I decided to remove the clock for rebuild and to replace the casette player with a CD player. May as well while I have this thing torn up. I will follow-up with the "rest of the story" as I progress. BTW, I am an accountant - not a mechanic! If I can do it, anybody can - just takes a few guts to tear into the thing.

1/24/2004

Received all my stuff from Corvette Central and performed the following this past weekend.

25. Disassembled the heater box and cleaned the old seals/gaskets. Cleaned all of the ductwork and center air distribution assembly as well. Used a single edge razor blade for scrapeing old gaskets/seals and acetone to clean the metal bezel holding the heater core. Soap and water w/brush for the rest.
26. Vacuum tested the two vacuum actuators (one on the heater box and one on the air distribution assembly). Be sure to vacuum test both sides of the actuators. I used a vacuum pump but the test could be done in true "bubba" style by mouth suction and eyeball if you want. Just need to verify that the actuators are not leaking. Both of mine were good.
27. Applied lithium grease to the metal parts of the actuator linkage that rub or rotate against other metal parts. (Same as the factory)
28. Fitted the new heator core to the heater core bezel. This took a little while to think through because the new one was not the precise fit as the old Harrison core. Couldn't find a source for a Harrison core so I settled for a CC replacement core. I worried about this for a while, but with some gentle nudging and slight and careful bending of the coolant entry and exit pipes, I got it to fit reasonably well.
29. Performed a 24 hour vacuum test on the new core before final assembly. Placed a vacuum on it of 20 in. hg. for 24 hours and detected no leakage. You could perform a pressure test if you wanted. Either way - test for leaks before reassembly! Wouldn't want to do this PITA job over again.
30. Opened the new heater box/-A/C ductwork gasket and seal package from CC. This package is a "generic" collection of seals and gaskets designed for the entire C-3 run. You have to think about what you are going to use out of the package. Once you determine which seals and gaskets to use, it is a very straightforward job to install them. There is a "generic" exploded picture of where the gaskets go, but you still have to use your judgement because of the variations to the system over the years. You will also get the A/C seals for the engine side with the rebuild kit so save those for that job when you get ready to do it.
31. Reinstalled heater core into the heater box and organized everything for reinstallation into the car.
32.Before I reinstall the rebuilt heater box/ductwork, I removed the passenger kick panel vent door actuator and vent door. performed a vacuum test to the actuator and cleaned/lubed the vent door to actuator linkage. Also vacuum cleaned the space behind the vent door location. There was an accumulation of dirt, leaves and crap inside it which could cause a body drainage problem. BTW, the vent door itself lifts out very easily once you disconnect the actuator assembly from it. Just be careful that you don't loose the retaining clip/speed nut holding the two together. The vent door just lifts up against a spring loaded top hinge. The bottom hinge will come out of its hinge hole and all you have to do is push the bottom hinge back into the vent passage and pull it out into the cabin by top hinge. The vent door gasket was in tatters so now I know why the cabin had hot air swirling through it the past five years. It just as well had not even been there. There is no vent on the drivers side of my car.

At this point, my confidence is high because I haven't run into any surprises and am making good progress for an amateur. Patience is the rule however. The most difficult thing I have encountered so far is twisting my body around to work on this thing.

Ordered the vent door rebuild kit (should have done this earlier but didn't think to do it). Red69 reminded me to do it. Thanks Red69!

I will write the reinstallation phase of this when I get ready for final reassembly and interior vacuum hose replacement. Probably within a few days. Anyway, thanks for the tips and words of encouragement - any and all comments/advice are welcome and I appreciate them.


Larry
 
L

Larry Langley

Guest
Forgot to mention - before I even started I read up on the heater core R&R procedure in my GM service manual and my Haynes manual. Looked carefully at the exploded pictures in the Assy. Inst. Manual. Also forgot - I also ordered a new heating and A/C vacuum hose kit. That procedure should be very straight forward as everything is color coded and should match with the existing hoses.
Might be a few days before I resume work as a cold snap hit here in Austin and I don't do well in a cold garage (55 years old).
 

Red69

Well-known member
Joined
Nov 30, 2003
Messages
107
Location
Sunshine State
Corvette
1969 coupe
Larry, while you are replacing the heater core is a good time to replace seals in the box. When I did this to my no air box all the seals were shot. The job was a PITA but the heater works as new. Another seal that goes bad and contributes to cabin heat is the astro vent door behind the kickpanel. These are relatively easy to do and make a big difference. I am not familiar with the AC model and just assume it is there. Be careful not to damage the interior firewall seal, they cost big bucks. Good luck with the project and keep us posted on progress.
 
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Larry Langley

Guest
Thanks Red69! I do intend to replace the heater box, distributer box and ductwork seals and gaskets. All of them are deteriorated and have long since been at the end of their useful life. Re the kickpanel, yes I do have one on my A/C model and the seal on the vent door is shot. I will replace it as well. I removed the kickpanel just after step 10 but forgot to say it. It was a simple step. I'll try to be as complete as I can while describing my progress. Short term memory at 55 yoa is frustratingly short lived.
 
6

69MnyPit

Guest
Might as well do mine. I got my 69 a few months ago-heater condition unknown. I already got the entire interior gutted to include windshield and dash and the paint stripped-getting ready to put it all back together after paint. Then I start on the engine compartment. Take care!
 

lone73

Well-known member
Joined
Sep 24, 2003
Messages
456
Location
Texas
Corvette
'73 4spd coupe, '04 6 speed coupe
Hey Larry,
Never seen you post here. you probably don't remember me but I introduced you to the Austin Shark group via e-mail about 6 months ago or so. I haven't had a chance to attend another meeting though. I take it you've been to a few? How is it going?
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.
.
 
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photovette

Guest
I did mine a couple of weeks ago. I feel for'ya brother!
 
L

Larry Langley

Guest
lone73 said:
Hey Larry,
Never seen you post here. you probably don't remember me but I introduced you to the Austin Shark group via e-mail about 6 months ago or so. I haven't had a chance to attend another meeting though. I take it you've been to a few? How is it going?
.
.
.


Hi lone73! Yes, I have participated with the Austin Sharks group a couple of times and find the members (just an informal email group) to be great guys and gals. Hope to see you soon. Right now I am performing some rather heavy maintenance and minor repairs on my 72. Been procrastinating but she is in the hangar for the winter now. Finally got her up on four jack stands about a foot off the cold!! garage floor. Should be ready for spring and summer cruising.
 
L

Larry Langley

Guest
photovette said:
I did mine a couple of weeks ago. I feel for'ya brother!

Frankly, I'd rather have a root canal done.
 

craig32

Well-known member
Joined
Sep 30, 2004
Messages
482
Location
PA
Corvette
1981 repainted black coupe
Larry, just how cold does it get in Austin Texas? It was 8 degrees below zero here in central PA this morning! Needless to say, 'plastic car' is in the garage during snow season. I'm amassing a pile of parts to put on her when it warms up to 40 or so. Good luck with your project.

Craig
 
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Larry Langley

Guest
craig32 said:
Larry, just how cold does it get in Austin Texas? It was 8 degrees below zero here in central PA this morning! Needless to say, 'plastic car' is in the garage during snow season. I'm amassing a pile of parts to put on her when it warms up to 40 or so. Good luck with your project.

Craig

Cold is a relative term here in Texas. When it gets around 45 or below it seems rather cold. At that point I quit mechanicing and go inside to give my main squeeze some needed attention and, ah, maintenance. We certainly don't get out with our "T" Tops off. I realize that its probably balmy for you poor souls in PA. By the way - Philadelphia looked great yesterday. Awsome game.
 
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bob69

Guest
I have a 69 heater box w/o air out of the car. I bought the rebuild kit but it appears I need to drill out quite a few rivets in order to put in some of the seals. I assume that was part of your 'disassembly'? Just wanted to make sure before I did something stupid!
Thanks for any response.


25. Disassembled the heater box and cleaned the old seals/gaskets. Cleaned all of the ductwork and center air distribution assembly as well. Used a single edge razor blade for scrapeing old gaskets/seals and acetone to clean the metal bezel holding the heater core. Soap and water w/brush for the rest.
 

Les Wetty

New member
Joined
Jul 25, 2014
Messages
2
Location
Pottstown, PA
Corvette
1972 LT-1 coupe
Re-Installation Phase of Heater Core R&R (1972 coupe)

Was there ever a post for the re-installation phase on the 1972 coupe with A/C by Larry Langley?
 

bill81vette

Moderator
Joined
Jan 17, 2004
Messages
4,321
Location
Troy,NY
Corvette
1981 dark blue metallic
Welcome to CAC!!!! enjoy!!! re installation should be the reverse of removal.
 

Les Wetty

New member
Joined
Jul 25, 2014
Messages
2
Location
Pottstown, PA
Corvette
1972 LT-1 coupe
Bill, thank you for the welcome. The core replacement on my 72 will be a challenge. And yes it makes sense that it goes back in reverse.
 
Joined
May 22, 2005
Messages
458
Location
Maryland
Corvette
2001 Z06
Bill, thank you for the welcome. The core replacement on my 72 will be a challenge. And yes it makes sense that it goes back in reverse.

There's a reason behind it being part #1. The car was built around the heater core, at least on the 89 I had until recently.
 

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