Heater core recommendation needed + another HVAC issue

[Matt B]

Originally Posted by Matt B

Talking about vacuum... I'm still looking for the exact source of the HVAC vacuum. Does it have a vacuum canister? If so that's a potential issue...

After spending the evening in my shop manual I finally found the relevant section under General Engine Mechanical. More on-car research tonight!

[Matt B]

So, I checked the vacuum system. I pulled 15 in hg from the canister/secondary air valve/cruise control branch. Absolutely no issues here.
Next I pulled vacuum directly at the plenum connector into the HVAC branch. Also super tight, no issues. Also the check valve seems to be fully operational.
So... I can't spot any unexpected behavior along with the HVAC vacuum circuit.

I will try to pull the modulator tomorrow and check for a potentially defect valve. But I doubt that this is the source of the noise I mentioned earlier.

Also the new heater core arrived today. Big day tomorrow...

[Matt B]

So, while I was in there... I decided to take the chance and fix my CDM holder. Both tabs were broken. Inspired by one of our brothers who did a similar job (just don't remember who...) I shaped two new tabs from a strip of aluminum and used pop rivets to attach them to the carrier.
Also I reinforced the rivets with washers to avoid that the brittle plastic breaks again.

I added some more washers to the cruise control module screws to gain clearance and compensate the rivets heads.

Built to last!
20220823_144552.jpg20220823_151100.jpg20220823_151109.jpg20220823_151622.jpg

[WARP TEN]

Originally Posted by Matt B

So, while I was in there... I decided to take the chance and fix my CDM holder. Both tabs were broken. Inspired by one of our brothers who did a similar job (just don't remember who...) I shaped two new tabs from a strip of aluminum and used pop rivets to attach them to the carrier.
Also I reinforced the rivets with washers to avoid that the brittle plastic breaks again.

I added some more washers to the cruise control module screws to gain clearance and compensate the rivets heads.

Built to last!
Attachment 18466Attachment 18467Attachment 18468Attachment 18469

Looks like a nicely done job Matt. --Bob

[Matt B]

Thanks, Bob!

However, now I'm stuck and need advise. I removed everything to gain access to the core. But at the end the shop manual isn't very precise...
My understanding is that I don't remove the entire heater core housing but only the rear cover. Is that correct?

If so, there are 2 things in my way which I can't remove/separate.
First is the hose that feeds the passenger door defrost. I removed the 2 screws that attach it to the heater core cover. But I don't see how I remove the hose. Do I just have to pull it towards the passenger door?

Second, there is a kind of cylindrical shape riveted to the heater core rear cover. Towards the passenger it connects to the interior temperature sensor hose. Towards the engine it connects to another hose that disappears behind the temperature control motor. There is little to no room to grab those hoses where they connect and separate them.
I tried to take a picture but it'll be hard to tell from that one...

Long story short: how do I finally remove the core when everything else has been taken out?20220823_183343.jpg20220823_183403.jpg

[secondchance]

Matt,

it has been a while since I did this work. And, secondly, I don't have very good memory.
What I do recall is fighting to get some pieces out and in some case, locating and removing 7mm hex purely by feeling it with my fingertips.
Also, I believe you are right that you need to remove the housing cover and not the entire housing.
I just kept removing pieces until I can pull and remove the heater core.

[Matt B]

Thanks, Yun. Sounds exactly like what I did - work on until there's nothing left to remove!

I found and removed all 7mm hex keys and can actually easily MOVE the cover. But I can't REMOVE it. Maybe I need to apply more brute force to get the clearance I need.
But I don't want to break anything that requires the whole center console and lower dash to be removed in order to fix it...

[secondchance]

Originally Posted by Matt B

Thanks, Yun. Sounds exactly like what I did - work on until there's nothing left to remove!

I found and removed all 7mm hex keys and can actually easily MOVE the cover. But I can't REMOVE it. Maybe I need to apply more brute force to get the clearance I need.
But I don't want to break anything that requires the whole center console and lower dash to be removed in order to fix it...

Us Zr1 owners (and C4 I presume) refer to the heater core as part #0000001 - the very first piece to be installed on the chassis.

[Matt B]

Hahaha, oh my God... That doesn't sound very promising.
But you may be right. It seems that EVERYTHING is in the way here...

[Matt B]

Finally!!! Not sure who designed this, but... SHAME!!! [emoji1787]

Seriously, this is a really nasty piece of work. If another brother has to go down that road I STRONGLY recommend to pull the dash, etc. It causes additional work but pays off easily the further you dig in.

I again studied the shop manual and realized that the horizontal tube runs all the way through the lower dash into the drivers footwell. There is another screw hidden behind the main wiring harness.
With that screw removed the tube first has to be pulled away from the rear heater core cover for about 2 to 3 inches to clear the connector between the two and then towards the passenger door.
What a tricky surprise at the end of the disassembly story...

Now everything is set and ready for reassembly. 20220824_183402.jpg