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2010 CTS (Elvis) 1964 Impala (Betty) 1991 Miata (Dolly)
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Discussion Starter #1
Replacing Heater Core 91 DeVille—Any advice?

Up until a few days ago, I was getting warm air out of the passenger side defroster vents, but now, it's just cold air. I've replaced the heater control valve and attempted to flush the core without success, so it looks like I'll have to change out the core (I think it's leaking a little, too). Driving home from work last night, the outside temperature was 35º, and I don't think it was much warmer inside the car.

The local NAPA store has a core for about $50, and I've downloaded a couple of posts from the site on changing out the core, plus I have directions in my shop manual. So I'm going to attempt the job tonight (I drove my Impala today so the Caddy will be cool when I start working on it).

What I'm looking for is any advice from anybody who has done this job. What kinds of problems come up, and how do you solve them? I've seen where access to the hose connections at the core are a problem. What's the simplest way to get to them, disconnect them from the old core and put them on the new one? I've replaced the spring-type hose clamps with screw-on clamps on the other hoses, but I suspect it has spring clamps at the core.

Are any special tools required (or helpful)? How long should the job take? I'll probably take twice as long since I'm not handy with tools. If anybody has any pictures, that'd help, too. I'll try to take some of my own for future reference.
 

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61 ragtop,2 67 eldos,68 ragtop,68CDV,93 ETC
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Re: Replacing Heater Core 91 DeVille—Any advice?

I just did the heater core on my 90 fleetwood tuesday and the only difficult part was removing the spring clamps on the hoses. I have a tool for removing them which has a cable with a sliding jaw clamp at one end and a squeeze grip at the other. I don't know how I could have gotten them off without it. As far as the heater core itself, it was a cake walk.
REMOVE OR DISCONNECT

1. Drain engine cooling system.
2. Heater core inlet/outlet hoses.
3. Right sound insulator.
4. Glove box module.
5. Air mix valve link.
6. Programmer vacuum and electrical connectors.
7. Heater core cover with programmer attached.
8. Heater core retaining screws and heater core.

I took the programmer off the heater core cover just to give me some more room but I don't think you would have to. I also did not drain the cooling system as very little coolant leaks out if you raise the hoses above the engine after removing them. Flat rate on this job is 2.7 hours and I think I had almost 2 into it by the time I was done. Also, when you put it back together you need to adjust the air mix door which is hooked to the threaded rod you removed from the programmer . The procedure is:

1. Remove glove box module.
2. Set temperature on Climate Control Panel (CCP) for 32°C (90°F) . Allow 1 to 2 minutes for programmer arm to travel to maximum heat position.
3. Snap threaded rod from plastic retainer on programmer output arm.
4. Check air mix valve for free travel. Push valve to maximum A/C position, and check for binding.
5. Pre-load air mix valve in maximum heat position by pulling the threaded rod to ensure the valve is sealing. Programmer output arm should be in maximum heat position.
6. Snap threaded rod into plastic retainer on programmer arm. Avoid moving programmer arm or air mix valve.
7. Set temperature on CCP for l6°C (60°F) . Verify the programmer arm and air mix valve travel to the max A/C position.
8. Install glove box module.
These are actually far easier than most heater cores these days. Good Luck!
 

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Re: Replacing Heater Core 91 DeVille—Any advice?

I agree, the hardest part is getting the heater hoses off at the firewall. ***Be sure your thermostat is working before replacing the core***

I did mine and found out the the stainless steel core was in perfect shape and all I needed was a new thermostat.:(

Good luck.
 

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2010 CTS (Elvis) 1964 Impala (Betty) 1991 Miata (Dolly)
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Discussion Starter #4
Re: Replacing Heater Core 91 DeVille—Any advice?

Thanks for the replies.

My back is sore, my hands bruised and cut, but I have heat.

Too me six hours, but four of that was probably getting the hoses off and back on. What a friggin' nightmare! I curse the miserable bastard who invented those godawful spring clamps. Ended up breaking the bottom hose off the old core.

Had a devil of a time putting the hoses on the new core. There's just no room to get your hands in and around the hose. But I managed to get them on enough to put the screw clamps on good and tight.

And when I took the car out, the heat kicked right in (Good thing since is was about 35º). Checked under the hood when I got home; no leaks.

Sheesh, I hope I'm done working on this car for a while.

BTW, Vista Cruiser, I changed out the thermostat when I flushed the cooling system last month. So changing the heater core was a last resort.

One last note: If you have AAA, the discount you get at NAPA can be really good on some parts. It knocked $9 off the price of the heater core, and $14 off the price of new brake pads and rotors.
 

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94 Fleetwood Brougham
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Re: Replacing Heater Core 91 DeVille—Any advice?

Out of curiosity, I flushed my core in my 91 (couldn't get my arms into get to the hoses to replace, which was my original plan) and got it opened up (see my thread on how I did it in the tech forum) and was measuring 160-165F out of the floor heater duct with a candy thermometer (don't let the wife see!).

I am curious what a new one pumps out. I ran it on 90 to max it, it was 20 degrees or so out, maybe 30 (was fighting freezing point early on, then it froze)
 

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2010 CTS (Elvis) 1964 Impala (Betty) 1991 Miata (Dolly)
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Discussion Starter #6
Re: Replacing Heater Core 91 DeVille—Any advice?

N0DIH said:
Out of curiosity, I flushed my core in my 91 (couldn't get my arms into get to the hoses to replace, which was my original plan) and got it opened up (see my thread on how I did it in the tech forum) and was measuring 160-165F out of the floor heater duct with a candy thermometer (don't let the wife see!).

I am curious what a new one pumps out. I ran it on 90 to max it, it was 20 degrees or so out, maybe 30 (was fighting freezing point early on, then it froze)
When I took it out for a test last night, it got hot pretty fast, so I turned the temperature down to 70º. This morning, it was about 35º on my drive to work, and I still had it set at 70º with the fan on Auto. About halfway to work (30 minute drive), I remembered a small thermometer I had in the car and stuck it on the carpet under the ducts. Got up to 110º pretty fast. Cooler air was coming out of the defroster vents, but it was very comfortable.

I would expect that if I stuck a thermometer into the duct itself, the temperature would be a good deal higher.
 

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Re: Replacing Heater Core 91 DeVille—Any advice?

I just attemped to do my heater core this afternoon. Got everything inside done then I moved onto the hoses. 2hours later I still dont have either one off. From what I read on here I guess I should just use a chisel and break the hoses off my old core? Do all the cores have plastic ends? I dont want to try pounding it off then discover its metal because I'll have an even bigger mess on my hands. Any input is appreciated.
 

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Re: Replacing Heater Core 91 DeVille—Any advice?

The old core (which is OEM as far as I know) had plastic inlet and outlet tubes with those cursed spring-type hose clamps. I managed to wriggle the top hose one off, but was having trouble with the bottom one, so I wriggled the heater core enough to break the bottom inlet tube.

Make sure you've got some old rags or towels around the core because the bottom hose will likely drip coolant (I spilled some onto the carpet and floor mat, but sprayed them down with Resolve; they appear to be OK). I had not driven the car yesterday and did not drain the radiator (the petcock, like most things on this car, is hard to reach), but I did remove the radiator cap to clear any remaining pressure in the system.

You may still have some trouble getting the remnats of the inlet tube out of the hose. I ended up having the disconnect the hose from the heater control valve, pull it out of the engine bay completely, then use a screwdriver to pry the remnants of the tube off the hose. Rethreading it under the A/C dryer (I think that's what it was), was a bitch.

The new core I bought at NAPA has metal inlet and outlet tubes. Once I got the bottom tube rethreaded into position, it wasn't too horrible getting it back on, but not easy, either.

The top hose was a real battle. There's just no room to work in there. Since the tube is metal, I used a screwdriver to bend it out slightly, giving me a little more room to get the top hose back on.

I may still take the car to my regular mechanic and see if he can get the hoses fully onto the tubes. I could barely get mine past the first indent, and I tightened the screw-on clamps as best I could, but I'm still concerned they might come loose.

Good luck. Sorry to say you're going to need it.
 

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Re: Replacing Heater Core 91 DeVille—Any advice?

Ok, I got my heatercore done in about 2hours today. I was easily able to break the hoses off the old core using a chisel and then i pulled them out from under the A/C parts (without disconnecting the other ends) and easily removed the clamps and the peices of the old core.

I did have some trouble getting the new top hose back on.. but I was able to get it on just a little bit and put a clamp on it. Then i ran the car for 4 or 5mins and once the hose got hot it slid on the rest of the way easily.

Thanks for all the help guys!

(PS. HEATER WORKS AWESOME!)
 
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