How do you remove and replace a heater core in a 1993 mercury topaz?

Answer 1

You May Not Have to Remove the Dashboard...

I just changed the heater core on my 1993 Topaz this weekend and was surprised how easily it can be done. I was afraid I would have to tear into the bowels of the dash, but wound up NOT having to. Mine has a 3.0L V6, so I can't guarantee it would be the same for the four cylinder, but it would be worth checking out.

The heater core is in a black plastic case under the center of the dash. This case is directly behind the plastic vents under the dash and to the left of the housing for what I believe is the blower motor (since it has a rounded bottom). If you lay down on the floor and look up you should see four screws in the heater core casing - two toward the face of the dash and two toward the firewall. The firewall, passenger side one is a bit of a bear to get to, since they put a flange on the case right where you want to stick your socket (and need to see!), but it is possible to get it out with the right combination of 1/4" extentions. I believe the screw heads are 10mm on those four. Once you have those out, you can pry the bottom half of the case down off the upper half. There is a sealant in the joint, so you may have to work at it a bit. Once it is free, you have to work to get it down past the vent piece (angling the side nearest the vent down and working it out and under the vent - it will not come all the way out). Once it is free, STOP!

The top and bottom halves of the case are molded to hold the heater core in position. The core essentially lays in the molded bottom half. Due to the limited clearance under the dash, the core and bottom half of the case have to come out together. Before you can do this, you will need to undo the hoses from the core fittings in the engine bay. You will need to drain the coolant from the system first (the petcock on the radiator will make this easy). I found it easiest to access the hose fittings from the top passenger side, but that is not to say that it is at all easy. There is no shortage of hard lines and fittings in the way. There IS access from below as well, but it really depedns on how the hose clamps are on there as to how you will be able to get at them. The real hard part is trying to get the hoses broken free from the fittings after the hose clamps are off. They heat seal to the tubes and you have almost no leverage in there to get them free. It can be done, but it is not fun.

If you haven't done so already, you may want to put down a towel or tarp down on the floor inside in case you spill any coolant while removing the case and core. I have an automatic transmission so the console kept me from being able to slide the case toward the seats. I don't know if this would be a problem on a manual or not. Due to the blower box being right next to the core case on the passenger side, you pretty much have to take it out the driver's side. You will have to depress the pedals as you go to make room, but it should slide right out that way. My old core had a couple foam pads stuck to it that my new one didn't have, so I peeled them off and stuck them on my new one. I would suggest washing and drying out the case to get any coolant out of it before dropping the new one in. If you wanted to put new sealant under the core and around the seal, you could, but I didn't bother and just left the old stuff intact.

I hate the line "Installation is reverse of removal," but it is fairly true in this case. You may have to quickly start the car to relieve the pressure on the brakes system so you can depress the brake pedal again to get it back in. Be careful to get the pipe fittings lined up with the holes in the firewall foam gasket so you don't rip it. Make sure the rib on the top half of the case drops into the groove on the lower half of the case. Replace the four screws to secure the core in the case. When it comes to putting the hose clamps back on, I found it helpful to have two people - one underneath to hold the clamp and one above to tighten it. Not quite as bad as getting them off, but still no fun.

Refill your cooling system, get it up to temperature, purge the air, and top it off and you should be good to go. I was pleasantly surprised at how quickly it went, but working on the engine side of things is definitely hard on the hands, so be prepared for a bit of frustration there. Have fun!

Basics for removing a heater coreHi,

Well you've happened to have caught me on a day when I am going to have to replace the heater core in my own 93 Tracer Wagon. Now these vehicles should be close enough in configuration as to be of help to you.

The first thing that I would recommend is that you go to the library and get a book on your specific car, usually by Chilton or some such author. In this book it should tell you specifically how to take out the heater core. Browse through the book first to make sure. If it doesn't give you enough information then go to the reference area of the library and find what is called a "Motor Manual" for your specific car. These books aren't usually allowed to be taken out of the library, but you can copy the pages that you need on their copier.

But to give you a quick overview of what you have to look forward to, here are some of the highlights: First drain the coolant. Locate the heater hoses at the firewall and disconnect them. Now here comes the fun part. Go into the interior and clean out the front of the car completely since you will be working there for quite a while and you don't want to lose any of the screws/parts among a bunch of junk laying on the floor. Start removing the dashboard, there are a bunch of screws on top near the windshield, some maybe on the side and underneath. If you have a floor shifter and a console this will be getting in your way while you are working and some of it may need to be removed. You will also have to disconnect and/or remove the radio and probably the speedometer and guage cluster unless you are able to get underneath and disconnect these things. NOW DON'T FORGET YOU ARE GOING TO HAVE TO PUT ALL OF THIS BACK TOGETHER AGAIN, SO GO SLOW AND IF YOU DON'T THINK THAT YOU CAN REMEBER WHERE THINGS GO, IT MIGHT BE A GOOD IDEA TO MARK SOME THINGS WITH A PIECE OF MASKING TAPE AND WRITE DOWN WHERE IT GOES TO.

Now once you get the dash off your almost home free. By this time you should be able to see all of the heater/air conditioner components, don't disconnect anything that you don't have to. Open up the heater core compartment and remove the heater core, be careful not to ruin any of the sponge rubber, rubber seals etc. that may be there. Pull out the old heater core and make sure that the one you are going to put in is identical to the one you just pulled out.

Now the process that you just went through is reversed. Just make sure that you replace EVERYTHING that you removed. Good luck.

Someone else may have a different way of doing this but from experience (40 years of being a mechanic) this is just about what you are going to be looking at, but never turn down another persons idea unless you know it won't work or will cost you more work in the end.

John