In the spring of 2005 I went to start the car after the winter and get it ready for the inner fender replacement. When I got in the car I noticed a small amount of antifreeze on the passenger floor mat. The heater core had started leaking! Luckily it was a small leak so far and didn't get onto the carpet or under the floor mat. Looks like I got another job ahead of me!

I drained the antifreeze and disconnected the heater hoses from the motor. I blew them out with compressed air to prevent anymore antifreeze from spilling in the car. Ford had them run into the car where they hook to the heater core, they don't terminate at the firewall. The glovebox was removed so they'll be more room to work. The heater hoses were disconnected from the heater core, and the heater control cables were removed from their dampers. They are all different lengths so they can't get mixed up. All wiring going to the heater box was disconnected from under the dash plus the blower motor was unplugged at the firewall in the engine compartment. After the two heater hoses for the defrosters were removed it was time to remove the heater box as an assembly. This is best done with two people. One stays in the car and supports it while the other removes the four nuts from around the blower motor. Now the heater box can be dropped down from under the dash and removed from the car.

It was placed on the work bench where the defroster plenum was removed. I had replaced the plenum right after I got the car with the better repro plastic one since the original cardboard one was disintegrating. Next all the metal spring clips were removed next that held the two heater case halves together. I gently plied the case apart. Surprise! The heater core area was plugged with leaves.

Upon opening the case I found the heater core packed with leaves. 7 years of ownership of the car and I had no clue. The heater and defroster had good heat the times I've used it. There were several types of leaves.

There was no evidence of mice which was a good sign. Their urine can do a lot of damage.

You can also see the foam was pretty much disintegrated from the damper and case.

I took the damper and heater core out. There was dark green discoloration on one corner of the core showing where the leak was. It's visible near the top left of the photo above.  I also unbolted the fan motor from the case. I cleaned off all the remaining old foam from the case and damper. The case was vacuumed out, washed off and then put off to the side. The damper was never painted from the factory so it was covered with surface rust. Being difficult to wire brush it was sand blasted with aluminum oxide.

The damper is in the bottom of the photo just before being sand blasted with aluminum oxide. It was the easiest thing to do to get inside a complicated part like it was.

Being visible in the center of this photo, it came out like new with no rust after being sand blasted. Not only was the rust history so was any glue or foam that I wasn't able to clean off before hand.

After sandblasting I wiped it down with lacquer thinner before hanging it up and priming it. After drying it was sprayed with black paint. It will never rust again like it had been.

Here's the damper hanging up after being primed and painted. Even though it's not visible it makes for a better restoration. It makes me feel better too :)

I also scuffed up the fan motor and squirrel cage plenum and repainted those black. The fan motor is visible in the engine compartment and the squirrel cage plenum is slightly visible in the passenger compartment. The motors wires were masked off to prevent overspray. The fresh air door that opens up by the front passengers feet was also repainted. Not pictured is the rectangular metal frame that goes around the core itself. It was also refinished the same as the damper was.

Here's the fan motor and the squirrel cage plenum right after being painted. The squirrel cage itself wasn't painted since it wouldn't come off the motor shaft to be sandblasted. Even with the set screw removed it wouldn't budge. I decided to leave it alone and reinstalled the set screw.

The heater box itself wasn't painted since it's molded fiberglass. It was never painted from the factory. I just wiped it down with a damp cloth with water.

I didn't get back to working on the heater box until the next week. The paint had more than enough time to dry. I bought a heater seal kit from Mustang's Unlimited and 3M 90 contact spray adhesive from Home Depot. I laid out all the foam pieces and figured out where they went. They were then spayed with the 3M 90 while the corresponding surfaces were sprayed on the damper and rectangular frame. Any areas I didn't want overspray were masked off. After letting it set up and dry to the touch I stuck the pieces on.

This is some of the foam pieces as they were being sprayed. The 3M 90 was the strongest glue that I could find that would work for this application. The 3M 77 is a lighter duty so I used the 90.

The heater box is now ready for reassembly. I cleaned of the workbench, put a clean towel down and reassembled it the opposite as I took it apart. The new heater core was put in place during this time. The foam on both ends of the damper had to be shaved down with a sharp razor blade due to the fact it was too thick to fit in the heater box. After getting it all back together, including the repro defroster plenum installed again, it was time to put it back in the car. The new gasket that goes to the cowl opening was installed at this time. One person lifted it up under the dash while the other put the four nuts back on the blower motor in the engine compartment.

The defroster ducts, damper cables, wiring, and new heater hoses and clamps were then installed. The heater cables need to be adjusted. Hook the ends on but leave the clips partially loose. Hold the cable with one hand near the clip while using the other hand to move the climate control levers. While doing this slowly move the cable back and forth where it goes under the clip. Soon you'll get the feel as it moves the damper without shifting the whole cable. This is when you tighten the clip down.

The glovebox was the last thing to go in and the job was done.

Luckily this car doesn't have air conditioning. Otherwise this heater core replacement and heater box restoration would have been much more involved.

Back in the car and all hooked up. Note the screws for the glovebox partially screwed back in. This was done so they wouldn't get lost.

The repainted fresh air door really stands out. The dull appearance on the upper left of the floor mat is from the leak. You can see where it was running down. The floor mat was cleaned up and treated with Son-of-a-Gun and the mark disappeared. I'm lucky it only got on the floor mat.

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