I did my red vette 2 years ago, but here goes!
It did go smoothly, but I took my time. Inside the car: I removed the seat for access, I laid down on the floor with my feet up (at times) to gain access to the heater plentum assembly. After I removed the carpet covers, etc. I removed ducts. The tricky one runs behind the radio to the driver side, I think. Once I had enough out of the way, I removed the front half of the heater plentum. There's two straps, they are fastened at the bottom. Remove the two fasteners, 9/32" (1/4") socket, and bend the bracket/straps up. The heater core should be slightly loose. Just work it out towards you by applying steady pressure, if you have to. You'll hang up a little, but keep working it around until it comes out. Took me 10 minutes, I remember that! I didn't have to replace the part an earlier post talked about, but I suggest it's a good idea to get one & put it in now.
Re-assembly is the same as dis-assembly. Someone mentioned keeping track of the hardware you remove, I suggest that. If you have a bench, card table, garage floor, anything to organize would help. I'd use one of those screw organizers from Home Depot, you can label where they went.

On the outside: I cut the hoses with a razor knife. Good time to replace these hoses and clamps. I didn't take anything off the car out here or any fasteners.

NOTE: there might be fastener around the heater pipes, I can't remember if I had to lossen the AC plentum to get to it, or if itr was even neccessary to loosen to remove. I think it holds the back half of the heater plentum (this remains in the car, holds the heater core) , but I found out I didn't have to loosen it to remove the heater core itself. I mention this so you don't pull your AC apart to get to this screw. (It's the only reason for pulling the AC plentum.)

The A/C is separate system (within the system) from the heater. The heater core is inside, the evaporator core (A/C part) is an outside system, ducted into the inside. In fact, most GM is built that way. The newat thing was: I didn't have to release my R12 (very expensive) in order to change the heater core.

I share the same as the rest, I stood there in awe when I was done. When you're halfway through, take a picture of your dash parts to impress your friends and family!! :crazy:

That's about as much as I can remember for now, I hope this elaboration helps. I did put down most of the issues I had, it really did go quite well. I think one can do it in 4 - 6 hours. I spent a lot of time trying to figure out if I was going to pull the AC or not. Just take your time & organize the parts, you'll do OK. It'll save you at least $600 in labor alone! By the way, I'd pressure check the new core, I remember someone telling me I got lucky. I didn't have mine checked, assumed it was OK.

 

Excellent!!! This detail helps a LOT. I'm printing it out now.
Thanks for the time you put into sharing this. I'm on my way. :seeya :auto:

 

I'm in the same boat w/my '91 & being in Hawaii I really, really do not need the heater, shocking right? Question: Where do you cut the hoses exactly & are there any negative functional effects aside from the obvious, no heat? And if anyone who has pics of an L98 that could be used to help specify it would be much appreciated. mahalo & aloha :)

 

I looked at the bypassed heater on the car when I was given it by my wife...

I looked up how much work it was...

I paid $580 for the vette shop to do the work...

My first labor shirk on the vert.

The only avantage to no heater is fewer leaks... the warm air in winter was what I wanted in my daily driver (Sacramento does get to freezing). Previous owner was a performance guy. But a bit foolish to not fix the leak imo.

If you're going to do it yourself and you haven't ripped one apart before, bring more than one lunch, and walk away when you get frustrated to cool off, the parts will go on, it's just so freeaking tight and there are a mixed batch of fasteners to deal with.

 

Use zip lock sandwich bags and a felt tip pen to keep track of where all the different fastners go.

 

The discussions last week really helped me get an idea of the heater core location and required time to r & r. However, since it's my daily driver, I decided to just bypass the core and replace it at a more convenient time.

First I removed the 4 machine screws holding the surge tank in place. Once the surge tank is pulled aside you can see the 3/4" I.D. hose running from the surge tank to the upper core fitting (about 7"). The 5/8" I.D. hose running from the core lower fitting to the thermostat casting (near the throttle body inlet - about 28") is below the 3/4' fitting on the firewall.

Once I saw how accessible the hoses and clamps were I went to the auto parts store and bought a 3/4" to 5/8" barbed fitting reducer for about $1.50 and 2 screw type hose clamps for $2.49.

First I removed the upper hose from the core and wedged it vertically behind an a/c part. (There's a small electrical connector fastened to the firewall with a stud and nut you might want to temporarily remove just to have more direct access to the lower hose clamp at this point) I removed the lower hose, stuffed the reducer into both hoses and tightened the new hose clamps. (I tied the clamps together with a piece of wire just to be safe - that's just me) Didn't have to cut anything except a plastic hose tie to allow the lower hose more freedom to be repositioned a little.

Remount the surge tank and that's it. :hurray:

So for about $5.00 and an hour's time I've now bypassed the core, only lost about 1/3 cup of coolant, and no more fumes in my face today during the drive to work. :flag


[Modified by brob9, 1:16 PM 5/3/2004]