Likely Heater Core Failure

[GOLDCYLON]

Originally Posted by Dynomite

Great Photos......but SCARY

https://www.youtube.com/watch?v=1fuWH0dYago


How I felt after pulling the dash

[HIZNHRZ]

Originally Posted by GOLDCYLON

Use this as an oppourtunity to clean the vents or consider a dash leather wrap upgrade opportunity . Repair the foamy felts that surround the AC vents. I used to joke about the heater core being GM part 000000000001A and then the GM guys designed the rest of the C4 around it. Some GM Engineer is still prob laughing his AZZ off. GC

The statement above in bold and italic's didn't mean much too me when I first read it. GC, now I understand exactly the point you were making!

[Dynomite]

Originally Posted by GOLDCYLON

https://www.youtube.com/watch?v=1fuWH0dYago


How I felt after pulling the dash

Daryll........

I just pulled a heater core on a 1990 ZR1 WITHOUT pulling the Dash

There is a little trick on removing one 7mm screws on top of the front vent connection (two 7mm screws). The first 7mm screw is easily removed using a 7mm combination ratchet wrench from underneath. The second top 7mm screw can be reached by taking a long (large) screw driver and pry out on the top duct and against the Heater Core housing top. That gives you just enough room to use a 7mm combination ratchet wrench followed by a needle nose to make the final turns on the 7mm top screw on that vent flange.

So there you have it....a new trick....one guy on Youtube said it was impossible but what does he know

Quickly......as I recall......all accomplished mostly with a 7mm 1/4 inch socket and various 1/4 inch extensions

Outside
1. Drain Coolant.
2. Disconnect Battery (I use a simple quick disconnect).
3. Remove two 7mm screws in Coolant Reservoir in front of Passenger side.
4. Remove two Heater Hoses from Heater Core and set aside the Coolant Reservoir with bottom hose still connected to Coolant System.
I had to cut the Heater Hose between the Coolant Reservoir and Heater Core to remove it.
Will go to Auto Parts with the old hose having a "U" bend and look at hoses finding one with the same "U" bend but longer and cut to fit.

Inside
1. Remove Passenger Seat (4 nuts and two electrical).
2. Remove hush panel two 7mm screws (and maybe one on right side also).
3. Disconnect light connector on Hush Panel and set Hush Panel aside.
4. Remove three 7mm screws at bottom of Heater Core Housing accessing from under right side Hush Panel area.
5. Remove one 7mm screw on right side of Heater Core Housing (half way down) accessing from under right side Hush Panel area.
6. Remove several 7mm screws back side of glove box.
7. Remove phillips screw front latch glove box and remove glove box.
8. Remove one top 7mm screw on left side that can be seen on Heater Core Housing from glove box area.
9. Remove one 7mm screw top right side Heater Core Housing that cannot be seen directly but use a mirror.
10. Remove bottom 7mm screw from Heater Core Housing holding air duct flange (there is a bottom and top screw).
Use a 7mm combination ratchet wrench.
11. Pry open a great space between Heater Core Housing and top duct with large screw driver.
12. Remove top 7mm screw from Heater Core Housing holding air duct flange.
I actually used a needle nose pliers to rotate the screw and lift out after it was loose using a 7mm combination ratchet wrench.
13. Now........wiggle out the Heater Core Housing down and out.
14. Remove bottom Heater Core holder screw and open Heater Core Holder.
16. Remove Heater Core.

Notes:
A. There are a couple wire holders held by fittings inserted in holes in the Heater Core Housing which you just slip out of the fitting and poke out holder once Heater Core Housing is removed.
B. The hoses to the Top Vent (one goes to the right and forward and one goes to left and rearward) have to be removed from the vent plastic tube.
C. The left Top Vent tube has to be pulled forward a bit (you can get a hand in the gap) as you pull down on the Heater Core Housing.
D. Make sure electrical connectors to the right side are not getting caught on the Heater Core Housing as you pull down on the Housing.
E. The wires that are under the Heater Core Housing have to be disconnected (3 or 4 connectors) to allow the Housing to be removed.
F. There is a vent tube connected (slip fit) to the vent from which the two bolts were removed in step 10, 11 and 12.
G. The Air Duct Flange has a nipple on it which helps if that flange is pulled from the Heater Core Housing at initial removal.
H. There is a 1/2 inch long flange (inside flange) on the Heater Core Housing where it connects to the main air tube to the left. That means it helps to initially pull/push the Heater Core Housing to the right when removing.

Replacement of Heater Core Housing will involve a magnetic 7mm 1/4 inch socket to insert the various 7mm screws



Actually pretty easy with the trick of step 11 to remove the 7mm screw in step 12.

See Item #1 and Item #2 Replacing the Heater Core and Heater Hose Connection

[GOLDCYLON]

Originally Posted by HIZNHRZ

The statement above in bold and italic's didn't mean much too me when I first read it. GC, now I understand exactly the point you were making!

Yep. Why not create an access door on the firewall to service the core?

Well I know why. the same reason the General dumbed down the DIC on the C6 because it would give the owner too much information that the service department wasnt making enough money.

[GOLDCYLON]

Originally Posted by Dynomite

Daryll........

I just pulled a heater core on a 1990 ZR1 WITHOUT pulling the Dash

There is a little trick on removing one 7mm screws on top of the front vent connection (two 7mm screws). The first 7mm screw is easily removed using a 7mm combination ratchet wrench from underneath. The second top 7mm screw can be reached by taking a long (large) screw driver and pry out on the top duct and against the Heater Core housing top. That gives you just enough room to use a 7mm combination ratchet wrench followed by a needle nose to make the final turns on the 7mm top screw on that vent flange.

So there you have it....a new trick....one guy on Youtube said it was impossible but what does he know

Quickly......as I recall......all accomplished mostly with a 7mm 1/4 inch socket and various 1/4 inch extensions

Outside
1. Drain Coolant.
2. Disconnect Battery (I use a simple quick disconnect).
3. Remove two 7mm screws in Coolant Reservoir in front of Passenger side.
4. Remove two Heater Hoses from Heater Core and set aside the Coolant Reservoir with bottom hose still connected to Coolant System.
I had to cut the Heater Hose between the Coolant Reservoir and Heater Core to remove it.

Inside
1. Remove Passenger Seat (4 nuts and two electrical).
2. Remove hush panel two 7mm screws (and maybe one on right side also).
3. Disconnect light connector on Hush Panel and set Hush Panel aside.
4. Remove three 7mm screws at bottom of Heater Core Housing accessing from under right side Hush Panel area.
5. Remove one 7mm screw on right side of Heater Core Housing (half way down) accessing from under right side Hush Panel area.
6. Remove several 7mm screws back side of glove box.
7. Remove phillips screw front latch glove box and remove glove box.
8. Remove one top 7mm screw on left side that can be seen on Heater Core Housing from glove box area.
9. Remove one 7mm screw top right side Heater Core Housing that cannot be seen directly but use a mirror.
10. Remove bottom 7mm screw from Heater Core Housing holding air duct flange (there is a bottom and top screw).
Use a 7mm combination ratchet wrench.
11. Pry open a great space between Heater Core Housing and top duct with large screw driver.
12. Remove top 7mm screw from Heater Core Housing holding air duct flange.
I actually used a needle nose pliers to rotate the screw and lift out after it was loose using a 7mm combination ratchet wrench.
13. Now........wiggle out the Heater Core Housing down and out.
14. Remove bottom Heater Core holder screw and open Heater Core Holder.
16. Remove Heater Core.

Replacement of Heater Core Housing will involve a magnetic 7mm 1/4 inch socket to insert the various 7mm screws

Actually pretty easy with the trick of step 11 to remove the 7mm screw in step 12.

Well I have to say Cliff that the General did not plan on the Amercian Farmer approach to out engineering a solution. Maybe your new forum handle should be "Scotty" he can damn near fix anything. Most folks dont know that an old tractor can be fixed with a screwdriver a pair of pliers and bailing wire.

Pretty slick and well done. Still a hell of a lot of work. Please tell me you HAD to replace your heater core on one of your rides and this was not simply done for two reasons.

1. You were bored after making a prototye tool and mowing down a bunch of soybeans and said, Sleep who needs sleep?

2. You simply love a challenge.

[Dynomite]

Originally Posted by GOLDCYLON

Well I have to say Cliff that the General did not plan on the Amercian Farmer approach to out engineering a solution. Maybe your new forum handle should be "Scotty" he can damn near fix anything. Most folks dont know that an old tractor can be fixed with a screwdriver a pair of pliers and bailing wire.

Pretty slick and well done. Still a hell of a lot of work. Please tell me you HAD to replace your heater core on one of your rides and this was not simply done for two reasons.

1. You were bored after making a prototye tool and mowing down a bunch of soybeans and said, Sleep who needs sleep?

2. You simply love a challenge.

Yes...had antifreeze on passenger side carpet and foggy windows. But also item #1 and item #2 above. That darn tool erases Codes so easily by just holding button (turn key on) until associated Code flashes and then release for 3 seconds and then press button one more time....DONE.

Since I am under the passenger side Hush Panel with carpet removed I disconnected and reconnected the INFL REST yellow connector a few times to make sure there is a good connection to the right side Accelerometers on the frame rail (Just in case).

Oh....and I have been under the Passenger side Before on another ZR1 monkeying with the CDM.....I say monkeying because that is a son-of-a-gun also

There are a few notes added in the Post #23 above........
I am replacing the leaking Heater Core with a New Copper/Brass Heater Core.

OK.....found out something very interesting.......which requires an experiment.

Replacing the Heater Core.

The Top of the Heater Outer Housing (the one that is removed) has the top dual conduits for two vents attached to the Heater Core Outer Housing by two rivets (defrost and vent into passenger side just below glove box). Those two Conduits (one forward to left and one rearward to right) actually stick out interfering with the removal and installation of the Heater Core Outer Housing. You can get the Outer Housing removed by wiggling and bending the plastic Heater Housing but it is difficult because of the two conduits on top attached to that housing by two rivets. the top Dual Conduits for the two vents were attached to Heater plastic hoses (defrost and vent into passenger side just below glove box) which the two plastic hoses could be disconnected allowing removal of the Heater Core Housing with this dual top conduit attached. Those two Heater Plastic Hoses would be almost impossible to re-install after the Heater Core Housing is positioned and wiggled back into position having to connect the two plastic hoses after the Heater Core Housing is in place.

But.......I solved the problem



This could be a major improvement to the Heater Core Housing Replacement issue which now is extremely difficult without pulling the dash.

The Details are described in Item #1 and Item #2 Replacing the Heater Core and Heater Hose Connection

[Dynomite]

There exists (existed for me) a coolant hose going from top of coolant reservoir to top heater core. It is a "J" shape with one end larger than the other. Cannot find that hose anywhere but can piece one together from Auto Parts back room coolant hoses using a plastic nipple.

So.....anyone know where this coolant hose might be available?

I cut the hose with a single edge razor blade to remove it from the Heater Core.....thinking it was readily available

[WVZR-1]

Originally Posted by Dynomite

There exists (existed for me) a coolant hose going from top of coolant reservoir to top heater core. It is a "J" shape with one end larger than the other. Cannot find that hose anywhere but can piece one together from Auto Parts back room coolant hoses using a plastic nipple.

So.....anyone know where this coolant hose might be available?

I cut the hose with a single edge razor blade to remove it from the Heater Core.....thinking it was readily available

10257254 GM NLA but Gates 19743 is likely still available. You might see if a local can change either to Dayco or Goodyear. Amazon should be good for the 19743. The Amazon image doesn't display the larger ID on the short leg so I'd maybe be skeptical and try local but it's a competitive change.

This might be a harder find but does display the larger diameter on the short leg, Continental Elite 64304. Amazon even shows a single of this available. Actually all Goodyear product could be possibly rebranded as Continental Elite including even the "Gatorback" belt product line.

[Dynomite]

Originally Posted by WVZR-1

10257254 GM NLA but Gates 19743 is likely still available. You might see if a local can change either to Dayco or Goodyear. Amazon should be good for the 19743. The Amazon image doesn't display the larger ID on the short leg so I'd maybe be skeptical and try local but it's a competitive change.

This might be a harder find but does display the larger diameter on the short leg, Continental Elite 64304. Amazon even shows a single of this available. Actually all Goodyear product could be possibly rebranded as Continental Elite including even the "Gatorback" belt product line.

Hi: There are several sources including WalMart for that Gates 19743 but none show larger end diameter on the "J".

The Continental ELite 64304 does show the larger diameter end and just have to make sure it is the right diameter.
Amazon has just one left in stock (as you suggest) and all others are out of stock....I think I will try Amazon as it "appears" correct but diameter is not listed.
I will let you know if it fits.......lots better than conglomeration (spliced with 90 deg nipple) I have on bench just in case with flared end.

I tried local GM Dealer and was told that part number no longer exists and he brought up the picture on his screen showing the part. They all were very impressed seeing the ZR-1 however

I was going to lay some rubber on their concrete parking lot so they can say it was a ZR-1 if anyone asked but thought better of that.....kind of like some posts I would like to leave on the Forum but some do not have my sense of humor

Thank you.....you just know stuff no one else knows

You are right up their with my local JD Parts guy who knows some parts numbers by memory.

[WVZR-1]

It would seem "odd" that the Gates product weren't correct because the part fits all '90+ C4 Corvettes BUT stranger things of course could happen. The Continental could be more easily found OR NAPA. It was quite early when I saw your post but I'd say a NAPA 11743 is correct. NAPA image doesn't seem to display the larger ID BUT in the NAPA spec for the product they mention the diameter IDs by dimension.

.72 for smaller ID and .92 for the larger ID on the short leg.

*** I did find a Gates "identifier" and the Gates is also spec'd at .72/.92 and I expect that Gates is actually the NAPA provider. That would explain the similarity of the images.

You "my friend" should have no trouble.