Heater Core Write Up

[86VickyLX]

well, so much for that...

a few lessons learned: apparently there are subtle differences between these cars, but at the same time i think the sticky could be updated to clarify a few things concerning the nuts on the three studs and what gets removed from where. when you read thru it all you see conflicting reports.

in any event, i finally got the plenum out ... after breaking it. and upon further inspection, there was in fact no way it was going to come out w/o breaking it. for whatever reason, there was a nut on that upper stud between the firewall and the black plastic of the heater blower assembly under the hood. so while i did remove the nut in sly's pic (next to the heater core tubes) it was still retained behind that molded plastic.


[ATTACH=CONFIG]41211[/ATTACH]

after it broke and plenum was removed, i had to back the stud out of the nut from the interior and could see the nut then fall down between. interestingly, looking at the diagram from the shop manual, it shows a nut in this position (between plastic and firewall), but only on the one lower stud closest to fender. the upper stud (and the other lower stud) should only have the nut in the engine compartment. maybe somebody screwed up at the factory. ?

so now i've got no way to secure the top of the box upon re-installation, which of course is problematic on many levels. i was half-tempted to jerry-rig it all back together in disgust, but realized that wouldn't be so smart, as it won't seal properly especially once the lower nuts are torqued, further pulling the top of the box away from the firewall.

hopefully someone somewhere sells a replacement plenum assembly. haven't even looked yet, but any leads appreciated.

not how i wanted to spend my 3 day weekend. time to give it a break for a few days while i look for new heater box.

Lincolnmania has an atc box plenum from an 89 crown vic. I pulled it myself. Its in one piece.

Like I said before, all heater core plenum bolts are supposed to be removed from the inside of the vehicle.

[sinistral]

Lincolnmania has an atc box plenum from an 89 crown vic. I pulled it myself. Its in one piece.

for sale? i'll shoot him a note... struck out last night looking online at the usual suspects...

Like I said before, all heater core plenum bolts are supposed to be removed from the inside of the vehicle.

how would you get to the nut on the top stud? it is tucked up against the firewall and dash support structure.

thanks.

[sly]

the insulation that is over it is peel-and-stick. You literally peel it away from the firewall and it uncovers that nut.

and with that being the only broken part... I would just glue it back together with some plastic welder epoxy and put a small strip of speed steel over it to act like a freaking gigantic washer when I put the nut back over it.

[86VickyLX]

for sale? i'll shoot him a note... struck out last night looking online at the usual suspects...


how would you get to the nut on the top stud? it is tucked up against the firewall and dash support structure.

thanks.

everything is for sale for the right price.
And you just pull the insulation up off the hook and push clip and out of the way.

[sinistral]

finally getting back around to this... had to walk away for a while. ;-)

'cept now i'm realizing my memory of where-stuff-went has started to fade.

edit:
okay, shop manual says the one w/ white stripe goes to the large actuator for the blend door (pictured) -- so where does this other larger hose go (also pictured)?

[sinistral]

(mod: you can delete the post above... figured it out)

[slack]

Where did it end up going?

[sly]

to the large ass actuator behind the glove box.

[VicCrownVic]

Heater Core Replacment for 1991 MGM w/ATC

About 9 months ago I said I would do a write up for the heater core replacement on my 91 MGM... After a lot of time spent not working on it, I think I've reached the point where I'm ready to post. So here's a test of the length limit for a single post.

The following procedure is based on my own experience replacing the heater core in my 1991 Mercury Grand Marquis. My car has ATC but there shouldn’t be too many differences for a non ATC car.
This procedure can be used as a guide for Mercury Grand Marquis and Ford Crown Victoria model year 1990-1991 (Lincoln Towncars are probably very similar). This guide may be very close to correct for newer models since the 90-91 dash is more similar to the newer models (at least up to 94). For 1989 and older models, look to the beginning of this thread.
This guide is a combination of how I did it and what I would do different next time. The steps can be performed in your own preferred order (where possible). This guide is broken into 3 sections: Driver Side, Engine Bay, and Passenger Side. This guide is not guaranteed to be complete or correct, please add any corrections or suggestions to the thread.

This guide does not imply any level of safety; you are solely responsible for your own safety. This does not mean that there is anything unsafe about the procedure, but that as a non-professional/backyard mechanic I am unable to guarantee any level of safety. If there are any safety precautions that need to be addressed, please add to the thread. (I'm sure GMN probably has some kind of site disclaimer somewhere.)
The airbag system may not need to be disabled for this procedure, but for peace of mind I will mention it. The 1991 Ford Shop Manual says that the airbag system’s backup power supply "is a capacitor that will leak down approximately 15 minutes after the battery is disconnected or in one minute if the battery positive cable is grounded."

Recommended tools:
3/8 inch drive ratchet
A couple of 3/8 inch drive extensions, various lengths
1/4 inch drive ratchet
Small 1/4 inch drive extension

5.5mm socket
7mm or 9/32 socket/nut driver
8mm or 5/16 socket or nut driver
10mm socket
11mm or 7/16 open end wrench
11mm or 7/16 socket
13mm deep-well socket
15mm socket

Phillips head screwdriver
Something small to push the tension clip on the headlight knob (jeweler’s screwdriver, pick, etc.)
Something to pry the gasket/weather strip from the old heater core

optional:
T20 Torx driver
Trim removal tools (some may say this is not optional)
Something to plug the heater core lines to prevent spillage


Driver Side
1. Remove RH and LH lower moldings
These trim pieces should just pull right off.






2. Remove the headlight switch knob
Push the tension clip by pushing a small tool, such as a jeweler’s screwdriver, pick, or similar tool into the notch at the base of the headlight knob.




3. Remove the finish panel
There are 8 screws that hold my finish panel on. You can use a T20 Torx driver, a 7mm socket, or a 9/32 socket. The screw directly above the steering column is easier to get at with a socket and a ratchet.
(Pay no attention to the radio being removed in the "after" picture, it does not need to be removed, these pictures were taken a few months apart.)




4. Remove three retaining screws along the windshield
The plastic part along the windshield can be pried up to reveal the 3 screws that need to be removed. Pry up the edge closest to you and pull it toward you.
The same tool used in the last step will be used here as well. There is one screw on the driver’s side, one on the passenger’s side, and one in the middle next to the auto headlight photo-sensor. The screw holding the photo-sensor to the dash does not need to be removed.




5. Remove the headlight switch
Using the same tool from the previous 2 steps, remove the 2 screws that hold the headlight switch mounting plate in place. Unhook the electrical connections and the side window defrost vent.




6. Remove the driver side kick panel
Pry the rubber insert out from around the hood release, then remove the large head christmas-tree clip located at the closest point to the firewall. It is possible to remove the kick panel without undoing anything else, but I would highly recommend at least unscrewing the Philips head screw just above and below the kick panel along the door frame. You will be less likely to bend/break the kick panel by undoing these two screws.






7. Remove the "knee pad"
This will require an 8mm or a 5/16 socket. There are 2 screws under the dash and 3 bolts up top under the trim molding that was removed in step 1. Remove the bottom 2 first then support the knee pad with your knee while you remove the top 3 bolts.
The location of the 3 upper bolts is easier to show in one picture with the steering column out of the way. At this point in the procedure the steering column will be nowhere near ready to drop.




8. Remove the reinforcement brace under the steering column and the trim panel above the pedals (as one unit)
The reinforcement brace should have 3 bolts, one is already out in the picture.
Once the bolts holding the reinforcement brace have been removed, with the plastic panel still attached, pull the brace toward the deriver seat along the underside of the steering column. The plastic panel will slide right out of the clip located just above brake pedal when pulled as described above. Remove the light socket form the left side of the pane and put the brace and panel assembly somewhere out of the way.







9. Move the shift indicator cable out of the way
With a 5.5mm socket, remove the screw that holds the shift indicator cable adjustor to the right side of the steering column. Slip the end of the cable off of the shift tube and move the shift indicator cable and adjustor out of the way to the left of the steering column. On mine I stuck it in the cavity where the rear window (tailgate) switch would be on a wagon. For wagons, and 92+, you will need to find someplace else to keep the cable adjustor out of the way, maybe zip-tying it out of the way or something.
DO NOT drop the steering column until this step has been completed.





10. Drop the steering column
DO NOT drop the steering column until step 9 has been completed.
There are four 13mm nuts that hold the steering column up. The one on the right closest to the firewall will require a deep-well socket. Once these 4 nuts are removed the steering column will drop and the steering wheel will be resting on the seat. I like to put the seat all the way back and the front of the seat all the way down. The first picture is looking straight up from the floor at the underside of the steering column.




11. Remove the two large bolts that secure the left side of the dash
A 15mm socket will be required to remove these two bolts, and you will also want 9 to 12 inch extension to get at the upper bolt. The upper bolt can be accessed through an access hole just above the fuse block.





Engine Bay
1. Remove the MAP sensor (for clearance)
I find the map sensor gets in the way for this part during the procedure. It’s easy enough to remove, just two 7/16 (or 11mm) nuts on the windshield side of the cowl, disconnect the electrical connector and the vacuum tube. If the wire harness is still mounted to the tab on the MAP bracket pull it out. You will have more room to see and work with the MAP sensor out of the way.




2. Disconnect the two heater hoses
The tool (wrench or socket) needed to undo the hose clamps will depend on the clamps that are installed. On my clamps, which I believe are the factory clamps, I used an 8mm or 5/16 inch wrench.
It would probably be a good idea to plug the heater core lines to prevent accidental spillage later.



3. Remove the retaining nut
An open end 7/16 or 11mm wrench seemed to be the best way (that I had) to get at this nut. The stud that it is screwed to seems much longer than it needs to be, but when you put things back together it helps hold the heater box up until you get the nut back on.



Passenger Side
1. Remove the plastic panel below the glove box
This panel is held on by three christmas-tree clips and a plastic screw-on retainer. I believe there are tools designed for pulling the christmas-tree clips, I just use whatever I can find and make work. The screw-on retainer can be removed with a Philips screwdriver or even your fingers. Once all the clips and the retainer are removed you will be able to get at the light mounted to the panel and twist it out of the panel.





2. Remove the two nuts at the bottom of the heater box
Pretty straight forward, I used a long extension to get at these with a 7/16 socket (11mm socket should also work).



3. Remove the Glove box
There are three screws below the glove box hinge remove these with the same 7mm socket or T20 torx driver that was used for the other screws earlier. Once the three screws are out, open the glove box and slide it to the right and you can just pull it out. You can also squeeze the sides of the glove box inward to get the stops to clear, but I prefer just shifting the box to one side and removing it that way.




4. Remove two bolts from the support brace on the left inside of the glove box cavity
Using a 5/16" or 8mm socket remove the two bolts on the left inside of the globe box cavity. If you forget these bolts it may actually feel like something is hanging up near the center of the dash when you try to pull the dash. There are two clips, behind the brace, that the blots screw into. If you don’t notice them and later find one on the floor but have no idea what it is, this is a reminder not to toss it.




5. Disconnect antenna wire, lower right of glove box cavity
Inside the bottom right of the glove box cavity you’ll find an antenna cable, it should pull out of the junction if you pull it toward the firewall. Mine actually pulled out on its own when I pulled the dash away from the firewall.



6. Remove the passenger side kick panel
Same as the driver side kick panel, remove the large head christmas-tree clip near the firewall, then unscrew the two screws along the door frame at the top and bottom of the kick panel.





7. Unscrew the ground wires under the kick panel
Using a 7mm or 9/32 socket, remove the ground screw under the kick panel that grounds the black and red wires to the body. Doing this seemed to allow me to pull the dash farther away from the fire wall.




8. Remove the bolt that secures the right side of the dash
Using a 10mm socket, remove the bolt that secures the right side of the dash to the car.



9. Pull the dash away from the firewall
Lift and pull, there’s not much to it as long as all the steps before this have been done.




10. Disconnect the white vacuum line and white air hose (ATC only?)
Both run alongside the air box and may be ATC only. The air hose connects to a fitting on the firewall and the vacuum line connects to a canister (vacuum actuator), both are connected just below the recirculation door.




11. Disconnect the BDA electric connector (ATC only?) and remove the support brace
Using a 5/16" or 8mm socket, unbolt the brace from the firewall and remove the electrical connector for the BDA just to the left of the brace.



12. Pull the heater box out enough to remove the heater core
It seemed that I had more room if I lifted the passenger side of the dash. The box will rest on top of wiring harness once you have it pulled out. Be careful not to tilt the box forward otherwise you will spill coolant.



13. Remove the cover that is over the top of the heater core
Using a 5/16" or 8mm socket, remove the four screws that hold the top cover over the heater core.




14. Pull the heater core out
The heater core may put up a fight when you try to pull it. If you must pry it out be careful not to break the plastic heater box that it is mounted in. Try not to ruin the foam gasket/weather strip that surrounds the heater core, you will likely want to reuse it if possible.



15. Pry the original weather strip/gasket from the old core and put it on the new one
When I put the new heater core in there was plenty of wiggle room. If there is wiggle room that means cold air can get around the core, I’m not sure if it’s enough cold air to really notice, but I figured since my weather strip/gasket was still in good shape I would try to reuse it.
I split the top and worked my way around with a flat screwdriver (a putty knife may also work). The gasket is glued on, so you just need to break the glue, and once the gasket is off slip it onto the new heater core. I actually left the weather strip on the new heater core, because it was so thin it really didn’t interfere with the old gasket. When I put then new heater core back in with the old gasket it fit snug, the way it should.



Follow the steps in reverse to put it all back together, and make sure the system is properly filled before going on a test drive.

[Mainemantom]

Thanks for the step by step procedure. I like the use of the red marks. Excellent job.

[VicCrownVic]

It took about 4 hours for me to comlplete the procedure and I wasn't even moving fast. If I had to do it again I seriously believe I could do it all in as little as 2 hours. A lot easier than I remember the 89 and down boxes being, but then again I don't think I have torn apart an older box dash since I was in my late teens.

[sly]

very nice write up. And dang... I thought the earlier boxes were bad with the screws... those have less in just the top of the dash only. Way more everywhere else.

[IPreferDIY]

Now there's something you just don't get from the DIY manuals. That's frickin' awesome.

[nfldfordltd]

Does anyone have any recommendations as to the best brand of replacement heater core? I just had my 88 Lincoln out for a little spin before bedtime and blew the 4th heater core in 9 years of owning the car. There was one that lasted all of a week in 2011.
Suggestions appreciated. I'm thinking I'm going to try a Motorcraft one this time around as different aftermarket brand parts are consistently failing.

[IPreferDIY]

I'm not aware of any brand issues, though I'm no expert. I wonder whether you might be having some kind of galvanic issue. Some call it electrolysis, but others say that's not the right word. It's basically a matter of having some kind of electrical issue that causes the aluminum to be eaten away. (I put an extra ground strap on my engine just in case.) On the other hand, I'm not sure if this sort of thing could result in the heater core being attacked selectively without affecting the rad.

I've also heard of people needing to put a flow restrictor at the heater core inlet since the pressure can be too high.