kidkodiak

Well I'm gonna have to do it myself rather than pay $1K+ for a shop to replace the heater core in my old Jeep. Reading all of the writeups I can find about it now.

One question though I can't find answer to... if I'm not working on the AC evaporator, do I still need to get the system evacuated? I'm replacing the core (and relays and blower motor just 'cus I can) but not anything AC related.

I dont' want to have the dash stripped off just to find that I screwed up and it's either "put it back together" or evacuate it into the atmosphere, which I won't do.

Any knowledgeable folks out there able to answer?
Thank ya kindly
KK

Black89

I've done a lot of heater cores in the past just not one in an XJ but I have never had to open up the AC system to perform the work. I'm gonna take a stab at it and say that it should be the same way and you won't have to open up the AC. Don't quote me on that bu maybe someone else who has done on will chime in.

Precept

I have had the dash out of my 89 Cherokee and I did not have to do anything with the AC. You get the blower out from under the hood and the relay from under the passenger side of the front dash. I have not removed the heater core though but I am inclined to agree with the other gentleman's comment.

jeep3200

Looking at the manual for a 1999 you need to open up the AC system to get the heater core out.

I am not sure it is the same for a 1990 since there is a body style change between the two. I would start planning as if you need to open the AC system and get new O-rings for all the connections you need to open or are only accessible when you have things taken that far apart so there are not leaks at those connections when it is back together.

kidkodiak

Awesome, thanks for the feedback guys!

JeepMoreDoor

I'm not sure either, but I just replaced my heater core in my 2000 and I had to recover my freon and open the AC system. I'm almost 99% sure you'd have to in a 1990 as well.

DFlintstone

If it's just a pinhole, (a little fogging, a little smell), the small one inch diameter, three inch long thing of Alumiseal has worked for me a number of times. It's just like fine aluminum powder, not the thick gunky stuff that is known to cause problems. I think at the very worst it might slow flow in your heater core....

Black89

Here's some info from a manual I was able to find with google:

Below is the process from the manual, sorry there are no pics,

Removal & Installation (Cherokee & Comanche)
1. Disconnect battery ground. Drain cooling system. Disconnect heater hoses at heater core inlet and outlet tubes. Disconnect blower motor wires and vent tube. Remove console (if equipped). Remove lower instrument panel.
2. Disconnect electrical connectors from blower motor resistors. Disconnect vacuum hose at vacuum motor. Cut plastic retaining strap holding blower housing to heater core housing.
3. Disconnect and remove heater control cable. Detach clip at rear of blower housing flange and remove retaining screws. Remove housing mounting nuts from studs on engine compartment side of dash panel. Remove right kick panel.
4. Remove instrument panel support bolt. Gently pull on right side of dash, then rotate housing downward and toward rear of vehicle to disengage housing studs from dash panel. Remove blower housing. Detach retaining screws and remove heater core by pulling it straight out of housing.
5. To install, reverse removal procedure. Ensure seal is cemented in place to prevent movement when blower assembly is installed. Connect heater hoses and fill cooling system.


And a link with some info



https://www.cherokeeforum.com/f2/hea...cement-151208/


I would say from all of this that on our earlier year XJ's that you should not have to get into the AC side of things.

spaceharrier

I just got done replacing the heater core on my '89 Laredo with AC.

I had to open up the AC, and I'm not sure how you could do the job without it. To get to the heater core you have to pull out the ducting assembly from under/behind the dash, and that contains the AC evaporator core. That ducting assembly does come apart so in theory you might be able to disassemble it in place -- leaving the evap core hanging from its hard lines -- but I don't see any practical way of getting to the screws, since they're on top of the duct box and there's little to no room around it to get to them.

Clumsy wrench tip: when you're removing said duct box with the evap core in it, be careful of the screw fittings which anchor it to the firewall. After ~25y the plastic around mine was quite brittle, and I snapped two of three off being clumsy with it.

kidkodiak

Ive replaced the fan blower motor and the blower motor resistor... both reasonably easy to get to. The relay is probably easy to get to as well since it's front dash side.

TBH, I'm lacking the motivation to open the dash all the way. It's not leaking badly... just a hint of burning coolant smell in the truck when the heater is blowing. I might just save the big project for the spring when the weather is nice and warm again.
I think I can limp along.

On a side note, the blower motor was rusted to heck and back in the inside. Hard to imagine how it was working and it makes me wonder if that wasn't the smell of burning silicone I was smelling when the fan was on high. The resistor was shot too, so even if I didn't finish my goal of replacing the heater core, I'm glad I got to do this much.