Well, mine finally died and I had my mechanic replace the heater core. Three years ago, (see above), I posted a wish that mine never would, but, even then, I couldn't slide my control from Cold to Hot, so I didn't have heat, anyway. After they did the new heater core, half the dash out and all, for $575, it would have been another 3 hours to take out the rest of the dash to feed the tubes and wires from the used Heater/AC control unit I bought, so I had a new heater core that didn't leak, but still no heat. Then I noticed the anti-freeze smell, again, but not as strong. Back to the shop, where they found a leak in one of the conduits and were going to try to solder or weld it in place inside the firewall/dash. However, since I haven't had heat for 3 winters, and winter is only 2 months long anyway, we skipped further surgery and went with a by-pass, so the system doesn't even go to my new heater core, but I have no leaks, the car's AC still works, the anti-freeze is stable and keeping the car at 185 degrees on the road and 200 at stop lights or heavy traffic.
If someone buys the car, someday, I've got them a new H/AC control panel for the dash, a new heater core to un-by-pass and run it to, and a great running old Vette to drive around in. For now, I'll drive it without heat (not so bad in Arizona) and enjoy the ride.
BTW, Happy Holidays, Merry Christmas, Happy New Year, and thanks, as always, for all the help, sympathy, solutions, and good wishes shared on this forum all year long.
Bruce Taylor
Hi Folks! I don’t usually post but changing the heater core in my 90 was worth writing up. I just completed my job and it took me 2 long days and I did take the seat out. The fellow above did a nice write up but I could not do it quite like he did. Not sure why, but I think he did a 92 whereas mine is a 90. I just thought it was worth pointing out the difference in the two approaches. After taking the seat out I looked up into the box area and I just could see no way at all to work anything in the area. I am 54 now and I can’t see that close either so I took a new approach. I took off the upper trim first. This is the piece that runs the whole width of the car on top of the dash. Only 5 screws hold this piece in but to get to them you must remove the cover for the gear shift (4 screws) then the cover for the HVAC (3 screws) and you must also pop the cover for the defrost vent (0 screws). Take all the vent covers off and you will have access to all the upper trim screws. Once this upper trim is out of the way things brighten up a lot! It allows removal of the brace (RH side) at your knees (4 bolts). Then you can cut lose the RH brace that holds the whole dash on the right side. It doesn’t need to come out but gives you just enough maneuverability to get the job done. I also had to unhook about 5 electric plugs and also remove the Bose Delco radio box(not the radio) (5 plugs). With the glove box out this will give you pretty fair access to the Heater box. Here is another problem : That hole in the front of the box not only has a flange on it but the pipe sticks into the box about 3 inches. Folks this was a show stopper except for the fact that pipe that sticks into the box simply slips onto the flange. With some creative fingers you can push it off and get the box out. Whew! The only problem is that I could not figure a way to get it back in once the box is in place. So I left it out as its purpose seems to be an ever so slight adjustment to the flow of air in that port. I could not find any adverse affect at all. In my case I was able to replace all box and core screws pretty easily. It did seem worth the extra effort. I ended up with an aluminum core replacement. I was very concerned about this. This core was even less area than the brass one so I was worried about the performance. I did a lot of research and found nothing definitive-all antidotal evidence at best. Bottom line I got 140 degree F on low fan (3) and 122 degree F on high speed (10)( 40 degrees outside). So I am happy with the core performance. Sorry I didn’t get any data with the old core as it had a big hole in it. The whole job did take 2 days but I don’t think this is something you want to rush through. There is too much to go wrong like forgetting screws, plugs, vacuum lines, hoses etc. All with big consequences.