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Re: Is changing the heater core on a C4 really that bad? (8/18)
 10/8/13 4:30pm
cco
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, - Canada

Vette(s):
1994 convertible, Polo Green 2 1G1YY32P9R5114269 ---------- 2006 Monterey Red Vert 1G1YY36U665125919----


Joined: 8/16/2013
Posts: 191

I would guess that that might be adviseable; if not necessary. But you already knew that didn't you. Smile

I've heard of this job and it's no fun at all. I sure hope mine stays intact for as long as I have it.

C.

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Colin
Re: Is changing the heater core on a C4 really that bad? (9/18)
 12/15/13 10:58pm
Big J's 90 vette
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Joined: 12/15/2013
Posts: 1

what year was the vette u did the core on
Re: Is changing the heater core on a C4 really that bad? (10/18)
 12/18/13 9:55pm
corvetteguru
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San Pedro, CA - USA

Vette(s):
1992 Polo Green Coupe 1987 Bright Red Coupe


Joined: 6/20/2013
Posts: 7

nice write up...

and it's a bitch on a good day... It took me 8 hrs to get it apart, I got the core in, then figured, "eh, I'll put it back together tomorrow (Sunday)." Yea... I got the flu and it took me another month before I got the time to put the rest of the dash back together. 



Re: Is changing the heater core on a C4 really that bad? (11/18)
 12/25/13 11:34pm
BATaylorEsq
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San Tan Valley, AZ - USA

Vette(s):
87 Red Coupe, not as pretty, had 213G miles, great running engine; got 20-21 around town, 27-28 on hwy; I got to drive a Vette, every day for 6 yrs. It was my first; so now I know what the fuss is all about. (Sold it 2015 for $3000, still ran great.)


Joined: 11/29/2009
Posts: 90

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



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Re: Is changing the heater core on a C4 really that bad? (12/18)
 1/7/14 9:40pm
Crouchley
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Pasadena, MD - USA

Vette(s):
69 big block & 90 L98 6 speed


Joined: 1/7/2014
Posts: 12

Hi Folks!  I donít 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 canít 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 doesnít 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 didnít get any data with the old core as it had a big hole in it.  The whole job did take 2 days but I donít 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.

Re: Is changing the heater core on a C4 really that bad? (13/18)
 1/7/14 11:02pm
cco
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, - Canada

Vette(s):
1994 convertible, Polo Green 2 1G1YY32P9R5114269 ---------- 2006 Monterey Red Vert 1G1YY36U665125919----


Joined: 8/16/2013
Posts: 191

After reading about you guys slugging it out, I'll get a shop to do mine should it need a replacement. I'd love to tackle it just to say I did it, but my back won't stand up to that abuse any more.
Fingers crossed that mine stays intact.

Kudos to you guys who did it yourselves.

C.

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Colin
Re: Is changing the heater core on a C4 really that bad? (14/18)
 2/21/14 3:04pm
Smokey
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Wills Point, TX - USA

Vette(s):
1992 C4 Pure 100% stock


Joined: 2/20/2014
Posts: 6

I'm the poster above and am a good wrench. BUT at 64 years old now things just don't move like they did 20 years ago much less 5-10 years ago so To the shop it will go when and if it decides it wants out. Just a question here though. Who made these heaters core's? Was it Harrison? It seems like that not only Corvette had this heater core problem but Chevrolet had a bad run of heater cores in all their model line...

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Re: Is changing the heater core on a C4 really that bad? (15/18)
 2/22/14 9:32am
Crouchley
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Pasadena, MD - USA

Vette(s):
69 big block & 90 L98 6 speed


Joined: 1/7/2014
Posts: 12

All I can say is 24 years on a core isnt all that bad.  People say you should change the coolant regularly, but I never did in the 18 years that I owned the car.  And I am not convinced if I did change the coolant I would have got any more life out of it.  This could be a new topic of discussion.  I would like to hear some actual data from the "not broke dont fix it" vs. "change the coolant every year" folks.  Any data out there?
Re: Is changing the heater core on a C4 really that bad? (16/18)
 11/3/14 11:58pm
vetster90
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Joined: 11/3/2014
Posts: 2

I have the same problem and do u wnat to come up and change mine.  lol.  Maybe I could call u to get a bit more information such as how long did it take ?.  Is this possible??  

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Re: Is changing the heater core on a C4 really that bad? (17/18)
 11/7/14 1:52am
vetster90
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Joined: 11/3/2014
Posts: 2

I notice in your pix that u replaced the stock radio.  How did u get around the issue of system error on the speedometer?  I might be easier if I could call u.  Could you send me your number and I can save you the long distance call.

B


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Re: Is changing the heater core on a C4 really that bad? (18/18)
 9/27/17 1:09am
Merlin49
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Fresno, CA - USA

Vette(s):
1990 C4 coupe, Bright Red, L98, auto (stock)


Joined: 6/12/2017
Posts: 4

Hey Crouchley, I have the same model C4 as you do and I am just now in the middle of a heater core change. So far I am into it for over 3-workdays on the heater alone, but I've had many other items to attend to along the way. I am fully restoring a 1990 coupe and this is my first Corvette, so the learning curve seems straight up. I have studied every post on here and have learned a LOT about the differences in various C4 Vet models. I have also studied ALL the factory service manuals from 88 to 94 on the subject, and made friends with a couple of old GM dealer techs that worked on these things. The C4 models are certainly NOT all the same. The 84 - 89 models don't have the glove compartment in the way, and as such have a completely different (and simpler) dash system. The 1990 model is the first year of the new dash design with glove compartment, and I think GM assembled those any way they could, just to get them out of the production plant. On the 90-91s they did some really stupid design work in the heating/AC system, especially putting the temp-control door motor on the "top" of the heater case (where it is totally inaccessible). At the urging of the GM dealers the factory redesigned the system in the mid-year 1992 models and at least moved the temp-control-motor to the "bottom" of the case where it was accessible. The 92-96 models were again redesigned and somewhat easier to access for repair. But the 90 and 91 models are the worst you can get. I bought my 1990 cheap because it had a heater core leak. Not being a GM guy I thought "gee how hard could it be to change a heater core". That quickly proved to be a really stupid mistake. As of now, I have now completely removed all my seats, center console, instrument panel and control panels, ALL dash trim and most of the right side of the dash frame up to the fuse box. Because I suspected problems with my temp-control-motor, I also had to remove the entire heater housing to access the motor on the top of the case (there is absolutely no way to get to it in the car). But in order to fully remove the entire heater case I also had to fully remove all the AC case on the engine-side of the firewall too (the stupid screws for the heater case were underneath the AC evaporator case from the engine side of the firewall). So now, I am just starting to reassemble the entire system, BUT I am having absolute fits trying to find new parts that fit correctly. I have tried 4 new heater cores (from 3 different sources) that do not fit correctly. The water tubes are 1/4" to long to correctly line up with the holes in my firewall. I finally just hogged out the holes to get the clearance I needed. Then on the temp-control motor, I got curious about the Chinese replacement I bought. So I disassembled it to find that it was full of cheap plastic gears and plastic shafts and a cheaper motor. I compared it to my original OEM motor that had brass bushings, metal shafts and mostly metal gears, and decided to re-lube it and reinstall my original. My gears and bearings were in like-new condition. It also tested perfect anyway. I sent the Chinese junk back for a refund. My next big problem is that I can't find a correctly made AC evaporator core. I have ordered 3 of those now from 3 different sources and they ALL come with the pressure switch sensor port welded in the wrong position. My original sensor was toward the engine. The 1990 evap. core I first bought had the port pointing down so the switch hits the AC evap. case. The 1989 core. I just received had the port pointing away from the engine toward the coolant expansion tank, (and the picture in their catalog showed it toward the engine, but that's not what they delivered). At least I can install this with only a slight extension of the connecting wires. So overall I have been delayed about 4 weeks in just trying to find the correct parts to get my system reassembled. By the time I finally get my Corvette heater/AC system all back in operating shape, I will have over 6-weeks of time wasted and mountains of frustrating disappointments. . . . SO as to the question of "Is changing the heater core on a C4 really that bad", my answer is simply WORSE. Much worse on a 1990. . . .

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