Here's what's going on.
Smell of coolant and windows fog up. Only thing I found odd was if I let the defrost go while the car sat for 10 minutes the windows cleared and it was fine. Guess the core stopped leaking for a bit?
My question is if there are any hints or tricks or am I set for what I am afraid of? A long bit of laying on my back working.

 

Just did mine this weekend, well not entirely the truth as I had so many issues I just gave up . Why I decided to try and do this is beyond me as my car is a summer toy anyway the plastic on both ends of the heater door was dry and brittle and broke. Once you eventually get to the core it is held in by some preformed metal strap at the bottom and mine was rusted in half. Had to make a strap out of perforated pipe strapping to get it to hold. I nought a spectra core and it didn't quite fit. The dash brace wouldn't go back in no matter how hard I pushed, it was about an inch away from bolting in so now my car has no dash brace . At the end I found out my blend motor was shot.\
Wish I never started , but I wish you luck next time I will just by pass this sob.

 

I bought a heater core from AutoZone. The pipes didn't quite fit right and I had to bend them to make them work.

I took the dash pad off, which makes it easier to get to the top two bolts that hold the heater housing to the firewall. Some people do it by feel from underneath.

 

I used the "fastguy method" (search the archives). Remove the passenger seat, hush panel, ecm, door motor, (don't break the white plastic clip), and support bar. The top bolt on the support bar is very difficult to get to. Its a 13mm bolt and I had to use a stubby wrench and then used a 1/2" ratchet with extension to turn the stubby wrench. (That bolt is in pretty tight and I couldn't get enough torque on it to losen it otherwise). I then removed 2 7mm screws that held some duct work on the front of the heater core box and disconnected the duct from an accordion style duct. Then I removed the 5 7mm screws holding on the cover. The top two were especially difficult to remove since they can't be seen. I had to sit on the ground and reach up on top of the cover. There is one on each side, you'll be able to touch them with a finger, but just barely. I just pretended I was blind and was eventually able to get a socket and extension on them. After the cover is off, you can see the core. It's held in with 2 7mm screws on the bottom. Remove the screws, disconnect the heater hoses in the engine compartment and pull out the core. You may have to cut the hoses if they've been on there a while. It took me 4 hours to get everything apart and 2 hours to get it back together. Now that I know what I'm doing, I'm sure I could do the whole job in about 4 hours, which is what the local mechanic quoted me for labor. He also said it'd come to about $350 total which is what gave me the courage to do it myself. I spent $70 on the core and about $30 on different size extensions, u-joints, etc. I didn't end up using all the tools I bought, but I like buying tools and I still saved $250. The job wasn't nearly as bad as I expected. Different years may be harder. It took me longer to replace my water pump or intake manifold gaskets.





The reason why I didn't have to take off the dash because I was able to bend the plastic piece out of the way underneath the dash to slide my hands inside to undo the straps instead of taking apart the whole entire dash apart just to completely remove the plastic piece from over the dash. Of course you have to unbolt some of the stuff out of the way, like the ECM and dash-door support bar. I think that bolt was either a 13mm or 14mm bolt. The you would take out as many 7mm or 10mm bolts off that big plastic cover until you can swing it open and feel the heater core. So what you would then is to bend it open, just try not to break it, insert your hands inside the bent cover, undo the 2 7mm bolts that strap the heater core down, pull the heater core out, and you're done. Do the reverse. It should be easier because now you can backtrack. Sure you can endure some painful bloody scratches along the way when you bend the cover to insert your hands in, but having those cuts are part of a man's job. I'm young and inexperienced as some would happily do dappily say and can do this job, so if a dumb college kid can do it, it shouldn't be too hard to figure out from there. I'd be more than happy to aid someone along the way if you live nearby Kathleen, FL.

In summary:

Halfway drain coolant
Remove seat
Remove under dash kick panel
You'll see the ECM right there so take your 13mm ratchet and extension and remove the 2 bolts that hold it.
Drop ECM
Take off the door control module
Remove that black metal bar that connects the dash to the door so its not in your way
Remove as many bolts as you can from that big black plastic cover that seal the heater core. I think they are either 7mm or 10mm bolts.
As soon as you do that, it will be flexible enough to pry and bend out of the way enough that you can stick you hand in there.
As you are upside down laying on the floor, feel around for bolts that hold the heater core through that plastic piece.
You should feel a strap that holds the bottom of the heater core. It is bolted on by 7mm bolts.
Remove the bolts and strap
Pull out the heater core and your job is halfway through.
Slide in the new heater core and do the reverse of the "underdash" disassembly instructions.

Hope this helps.

 

Would it be easier to remove this from the engine compartment, if say, i had the engine removed? or is there things on the inside that need to come off first?

 

Nope, it has to be removed from the interior side.



Me too...Info found in this thread ---> HERE

 

Agent 86's version (with lots of pics) is here:

http://forums.corvetteforum.com/1569252027-post4.html

A little later in the thread that post came from he posted this picture. I guess he was a little frustrated:

 

I replaced the core in my ’87 a few months ago. I have created a procedure document, with pictures. If you want a copy, send a request to cesmachines@yahoo.com and I would be glad to send it to you.