Replacing the heater core in a 1993 Buick Roadmaster Estate

1993 Fleetwoods and Roadmaster are bascially the same chassis. You may need to make modifications to the procedure I've outlined if your car is somewhat different.

Note: my 1993 Roadmaster has factory automatic air conditioning.

Tools:

Long thin flat bladed screwdriver
Long handle water pump pliers
13mm socket
7mm socket (¼ inch drive) and various short extensions
¼ inch drive ratchet
7mm nut driver (optional)
WD-40 spray
Heat gun (very useful)
Utility knife
Towel or rag to catch coolant inside the car.

Ok, here’s how I did it. Feel free to modify this approach to suit your particular circumstances.

Underhood approach:

I didn’t drain the coolant and I didn’t disconnect the battery. You may choose to do both these tasks.

Remove the wiper motor. Believe me, this is the ONLY way those hoses and quick connects are coming off in 1 piece, as access is extremely limited with the wiper motor blocking access to the hose disconnects.

Removing the wiper motor is an involved but easy task and is outlined in the factory service manual so I won’t cover it here in detail.

But here are some basics.

Disconnect the wiring harnesses to the wiper motor. Remove the passenger side wiper, remove the long rubber cowl seal, remove the DRIVER’S side cowl vent cover, remove the passenger side cowl vent cover, remove the access plate on the passenger side, disconnect the wiper motor linkage from the motor (2 bolts) and then remove 3 bolts holding the motor to the cowl, and remove it.

Now you have clear access to the hoses and quick connects.

Remove the single bolt securing the outlet hose to the cowl. Now both hoses and quick connects can rotate on their axis (this will be useful later).

Spray the quick connects with WD-40 and let it soak in. Fire up the heat gun and heat the quick connects until the WD-40 starts smoking. The quick connects are easiest to remove once they are hot and soft.

Note: Pulling on the hoses while trying to release the disconnects WILL NOT help release the disconnects – in fact, it makes the disconnect dig in deeper. If anything, you want to PUSH the hose toward the firewall while attempting to release the quick connects.

Also, the nylon quick connect “cages” are available aftermarket from www.dormanproducts.com, if the nylon cage is broken or damaged during removal.

I used the long thin flat bladed screwdriver to “persuade” the tab to slide out of the notch thereby releasing the quick connect. You’ll have to grip and turn the quick connect to see/access the opposite tab & notch.

Repeat the WD40 and heat cycle with the other disconnect, until you can pull it off too.

This is a frustrating process but it can be done if you’re patient.

When the hose finally release, take care to catch any O-rings or nylon sealing rings that may be loose or falling out of the hose ends. Note there stacking order so you can replace them correctly during re-assembly.

Lastly, remove the rubber elbow at the firewall (this 90deg elbow is attached to the AC drain.)

Ok, once the hoses are disconnected, you can turn your attention to the inside of the car.

Inside the car approach:

There are several 7mm screws securing the hush panel – remove these and the hush panel.

Remove the 7mm screws securing the bottom cover of the core casing. There are 2 screws right up against the firewall and they are a bit of a challenge to access.

For the leftmost firewall screw I wound up cutting the black rubber?? firewall insulation with a utility knife to give me enough room to use a ¼ ratchet and 1-inch extension with a 7mm socket. I did NOT re-install this screw during the re-assembly process.

For the rightmost firewall screw, I used a ratcheting box-end wrench that I found at Sears. The wrench has a 7mm box-end and an 8mm box-end, with both ends vertically offset. Due to the limited vertical clearance surrounding this screw, this ratcheting box-end wrench was a lifesaver!

At this point the bottom cover will come off with some judicious pulling. Note that the AC drain port will cause a hang-up and you’ll have to pull the cover backward toward the rear of the car to fully release the bottom cover.

Once the cover is off, you’ll see the heater core is retained by 2 braces. Remove the braces carefully (the one nearest the firewall is a little tricky – you’ll see what I mean when you see it.)

Place a towel or plastic on the carpet to catch the little bit of coolant that will dribble out of the heater core when you remove it.

After the braces are off, you can gently pull the heater core down and rearward. I had someone assist me in the engine compartment to ensure the quick connects did not get hung up and break.

My new heater core did not look like my old one, until I realized I had to rotate the inlet and outlet pipes 180deg – then they matched perfectly.

Remove the little pipe brace from the old heater core and transfer it to the new heater core.

Installation of the new core is basically the reverse of the previous steps.

You may want to delay installing the bottom cover until you are able to fire up the engine and watch to make sure that there are no leaks!

Lastly, this is a great time to strip and re-paint the wiper arms so that they have a nice, smooth black finish, instead of flaking black paint!

Good luck!