: Re: heater core replacemant

09-07-06, 08:29 AM
Procedure to replace a heater core in a 96DeVille:

1) Remove the negative terminal on the battery. You're going to be working around the passanger airbag and pulling electrical connectors of the A/C Programer. Good idea to kill the power.

2) Open glove box and observe the access door in the rear. You are going to open this. Give a good tug on the left end of the door and pull straight in. Give it a good one, it will pop open. Un-clip the airbag connector that's clipped in place.

3) Remove the glove box. Six torque screws hold the glove box in place. Four on the front [open the door first] and two on the glove box floor. If you don't have appropriate torque drive a hex drive will work [especially on those two on the box floor]. Don't worry about the electricl wires plgged into the left end of the box. Pull straight out and then rotate the assembly off to the left out of the way - no need to unhook all that stuff and tempt Murphy.

Nice thing is that you will be working though this opening and not standing on your head under the dash, most of the time!

4) Under the dash panel is a black plastic sound panel that needs to be removed. Its held in place by three 7mm screw nuts along the near edge. Remove these and the panel will drop down and pull out. If your old core sprung a leak this caught some of the coolant - take care and wash the foam on the rear of the panel. Hot water and soap in the kitchen sink will do.

5) You are going to want to protect the left front fender while you attempt pulling and installing the heater hoses. Once done, pull the heater hoses on the engine side of the fire wall. This is a pain in that there's hardly enough room and it is a two handed operation. Take care not to damage the hoses - new sets are dear. Also watch out for all those vacume lines and electric lines that are right there crowded in and around. Keep in mind you are going to hook these up to the new core. That will prove more difficult.

6) Back inside the cabin take a look inside the glove box opening. Tucked away back to the right of things, way up there, you will see a silver box with colored vacume lines attached to its bracket. This is the A/C Programer. Look closely and you will see a single screw nut on the right end of the bracket. This is what you need to remove. Take care and do not drop that screw nut. You will never find it and will need to replace or, as I did, improvise to get it back together.

With the screw nut removed the whole A/C Programer unit wil be free and you will be able to wiggle it out and down. Move connectors as needed and take care with those vacume lines. Do not try to pull these. Don't want to think about trying to replace that stuff and remember Murphy. With the unit down flip it and pull the electric connectors off the progamers bottom edge. They release with a clip connection on the back side - pinch and pull.

Object here is to make room to the right side of that black plastic box you're seeing. This is the heater box.

7) Look on top of the heater box. You will see a control rod. Un-clip this on the right side, where it clips onto a white plastic control piece. All you need is a screwdriver under the rod on the right end and twist to pop it out of its groved retainer.

8) The heater box is split vertically in its center and is held together by two screw nuts. One you can see by looking through the glove box opening, the other is about six inches below it. Remove these and open the heater box to the right to expose the heater core.

9) The core is held in place by an end bracket secured by two screw nuts. Remove this bracket and give the core a good wiggle and pull it out and down into the cabin as best you can. You are pulling the hose stubs through the fire wall and it will come out.

10) The replacement core should come with a new bracket and air seals. Looking inside the box, where the core was you will see four strips of foam surrounding the opening. These should be replaced. It's tight in there, but take your time.

11) Install the new core once the air seals are replaced and secure it with the new bracket. Then go out and hook up those heater hoses. You are going to be pushing and twisting, but get them home and tighten the clamps well. With this done go back inside and give the core a good push towards the firewall. Recheck the bracket. The core should be in there firm as a rock.

12) All that's left is to put things back together in reverse of taking it apart.

Not bad 'eh? Book says two hour job, good luck. I've attached a pic showing how my core failed. Not what I expected.

09-07-06, 06:06 PM
man 2hrs is draggin! i used to do them in 20-30 min! of course i've done hundreds! lol thank god no more!

p.s great artical for the newbies!

09-26-06, 01:21 PM
20 to 30 min huh?? Is that including getting the RO from dispatch, going to parts, and getting the car in your bay? Damn. :worship:

09-26-06, 06:10 PM
I thought it was mentioned that the engine had to be tilted forward in order to get to the heater core or is it the blower motor?

09-26-06, 08:28 PM
electronic ro-- no dispatcher--- parts in stock. stall 20ft from parts counter. car on svc drive...yep 20-30 min...i think it paid 2.5-3.0hrs flat rate but i could be off on the flat rate. BUT thank god no more! lol
one of my friends works at ---rbm of atl--- mercedes dealer-- used to work at caddy said that the mercedes is a real p.o.s.. is it true?

09-27-06, 05:06 AM
No more then any other car, although my Caddy has had no problems at all. Mercedes are very well engineered, it's the out sourced parts that suck. Window switch's, regulators, engine mounts, ect. It's funny, I have to do a heater core for someone this saturday on a 97 Seville. I'll post how long it takes me.

10-18-06, 10:52 AM
Is this process very different from replacing the heater core on a 95 cadillac seville sts?

01-08-07, 01:13 PM
Krimson cardinal thanks used this to replace the heater core in my 97 Deville did it in about an hour removing and replacing and it was my first time replacing a heater core Thanks Krimson cardinal

02-11-08, 04:44 PM
Wow! Thanks, I need to do a '95 DeVille this week.

02-17-08, 10:15 PM
I thought it was mentioned that the engine had to be tilted forward in order to get to the heater core or is it the blower motor?
You're thinking of the blower motor.

01-24-09, 08:30 PM
Thanks, going to work on this sometime this week..sorry to bump an old thread, but this is really a great tutorial on replacing the heater core. Going to print off now. Thanks again

03-28-10, 11:58 AM
Your htr core replacement might help me determine if i can replace the ac evaporator core in my 97 eldorado! I hve been unable to date to locate any information on the removal of the evaporator. Did you see it when you removed the htr core? Cadillac does not even show or mention it in their chilton information book. Please give me any info you guys may have on the removal of the evaporator. Thanks.

04-02-10, 09:57 PM
This section is for Tips, not questions. You'll get more help posting in the Seville/Eldo forum.

Cadillac does not even show or mention it in their chilton information book.
Chiltons and Haynes are not put out or written by Cadillac or GM and are useless for all but the most basic of repairs. Get a GM FSM by Helm Inc.

07-13-11, 08:32 PM
well this thread really helped me get the job done in an hour ! thanks man step by step and was done in a jiffy ! accurate to the t.......

09-26-11, 11:19 PM
All i can say is woooooooooooooooow, its great to know there are people like you out there, if it were not for your thoughtfulness i would have been screwed, thanks for savin me some big bucks.

10-28-11, 04:55 PM
How hard is it to replace the hoses if there is a hole in them? Mine is leaking outside the firewall and inside the cabin. I haven't taken it apart yet, but wanted to know incase i need to replace the hose.

10-30-11, 04:42 PM
Post your questions in the Deville forum. This forum is for Tech "TIPS". You are not as likely to get help here.

01-15-12, 12:21 AM
Many thanks for your detailed instructions, krimson_cardnal. My heater core blew while my 96 deville was in the middle of a smog test. There was sure a lot of "smog" in the cabin! I had to have it towed home. The plastic end with the hose fittings failed.

New heater core is a Spectra-Premium from Pep Boys. It is all-aluminum, so I hope it will hold up better than the original core.

Getting the hose clamps off was much easier after I got flexible hose clamp pliers (Astro Pneumatic 9409A via Amazon). The "OEM" brand tool from Pep Boys was not able to close the jaws enough to open the clamps so I had to return it.

The vacuum source from the firewall to the A/C programmer has a fitting halfway along its length. I twisted and pulled the connector apart and that enabled me to get the programmer completely out of the way toward the centerline of the car.

Just a reminder to be careful not to force the white control arm of the heat servo on the top right of the heater box (i.e., what the heat control rod connects to). If you force it to rotate, you can break the plastic gears inside the servo unit. A guy who did some A/C work for me a few years ago tried that and I had to do my own repairs after he finished.

Here are pictures. It seems I have just about reached my upload size limit, so if some kind moderator is able/willing to bump it up I'd be grateful :-)

The hose clamp tool

Looking into the glove box

The airbag connector

Remove these three torx (T15) screws on the left

Remove these three T15 screws on the right

The glovebox opening with the glovebox out of the way to the left

Location of the 7mm A/C programmer screw

The top of the heater core box

The A/C programmer removed

Bottom view of the heater core box

06-24-12, 08:48 AM
you have to do that for the blower motor.

09-30-12, 06:11 PM
goin to give it the ol college try on my mothers 96 eldorado this week its this or pay those shop rates ouch !!!!! thanks 4 the info

01-20-13, 08:09 PM
Thanks for the great thread! Well, I am a slow worker. I got it done over two days. I worked slowly with plenty of distractions. Maybe it was four hours of work? Maybe six? (Maybe more - I am a real snail with lots of distractions).

I want to add a few things. The parts store didn't have an OEM heater core. The replacement they sold worked well. However, the bracket was too large and kept the heater box from closing on with the heater core in it. I got around this by using a hack saw to cut away a little of the middle of the bracket where the box was hitting it. (I only need to cut a thin slice out of it - cutting a slice half as thick as a deck of cards would be more than enough.) The hoses went on very easy. I was expecting a struggle, but the went right on and tightened up good. It also did not come with new air seals.

I removed all the electrical connectors to the glove box. And I removed all the electrical connectors and the vacuum lines (they all come off together as one unit) from the A/C programmer with no trouble. (Murphy stayed away).

The heater box and heater core mounting bracket were secured with 5.5mm screw nuts.

My heater core failed exactly like your did. The replacement was all metal.

All in all, if a newbie like me can get this done - pretty much anyone can. Thanks for the great write up :)

05-05-13, 10:32 PM
Great thread! Had exactly the same problem as topicstarter: cracked plastic insert in the heater core. Fixed it in two hours including time to buy the part.

05-19-13, 02:22 AM
Would a blown head gasket cause a heater core to go bad?

07-15-13, 11:55 PM
Thanks a bunch to the OP for saving me time and money! Could have done without the shoe full of super hot coolant and 3rd degree burns but stuff happens.
Got it replaced in about 2 hours (Keep in mind im in gimp mode lol)

Anytime i have a problem, this is the first place i check and i always find an answer. Now registered and plan on spending a lot more time here. So much to learn!
Big thanks to the CF!!!

07-20-13, 03:03 PM
Does this process go similarly to a 95 Eldorado?

07-21-13, 09:25 PM
Should be similar.

10-22-13, 06:00 PM
Awesome write up. Worked perfect for my 97 Deville. Except on the 97 there is also a bottom air door arm you have to unsnap on the heater box. I had it knocked out in roughly two hours. But I smoked a bunch of cigarettes and took my merry time. Excellent information source.

11-04-13, 04:14 PM
Wow thanks for this write up. Had to replace mine today and this made the job so much easier

01-20-14, 03:35 AM
Best write up and most helpful pics I ever seen. FSM was vague. Took me under an hour to remove core from my 99 Eldorado. Much thanks to the original poster. I learned lot about Caddy Care 101 from this awesome site. I hope to contribute where I can as I explore my own pitfalls of a Caddy Northstar.

02-03-14, 04:19 PM
krimson_cardnal Just want to say Thank You for the nice write up on how to do this. I am doing it on my 96 Seville SLS now. If not for this post not sure I would have wanted to mess with it. So thank you. :thumbsup:

10-06-14, 04:05 PM
man 2hrs is draggin! i used to do them in 20-30 min! of course i've done hundreds! lol thank god no more!

p.s great artical for the newbies!

Can anyone give a definitive answer as to whether or not this short cut would be a go on 98-04 SLS ?

10-06-14, 09:39 PM
Can anyone give a definitive answer as to whether or not this short cut would be a go on 98-04 SLS ?

Different (very) car from Post #1. Use www.alldatadiy.com (http://www.alldatadiy.com) or dig deeper into the Google "cadillac forums Seville heater core replacement" threads.

10-06-14, 10:31 PM
No shortcut. Dash out, HVAC assembly torn down, reverse.

04-05-15, 12:01 AM
Replying to thread to indicate that it was VERY helpful for showing how to replace the cover for the heater core. In particular, the part about the screw for
panel holding the computer/vacuum distribution was very helpful [I did manage to drop it, and of course, it went behind the rug and was a PITA to retrieve].

My dad had broken it in a couple of places while figuring out what was going wrong with the heater [kind of necessary here in Edmonton, Alberta] and
didn't know that removing that computer/vacuum panel gives just that little bit extra clearance to be able to get the cover out without damaging it.

Turned out it was passenger actuator [which failed in a bizarre way, it's motor/gearing was so strong, it pushed/wore off
both plastic stops, so it would rotate 360 degree's]. We also replaced the Heater/A/C computer, but now I'm not so sure that was necessary,
as I'm sure that it would have been confused while trying to find the control arm limits when the system gets power.

I'm now working on the A/C side of the system, replacing the compressor because it's seized. I just hope the A/C core is OK, because I really don't want
to have to pull/drop the motor in order to replace it.