Fox-Body Ford Mustang Heater Core Replacement

Unbolt this bracket from the firewall that holds the heater case in position at the top. The case doesn't have to be removed, but it must move enough to allow you to open the evaporator case and remove the heater core.

Under the hood, unbolt the nuts that hold the evaporator case to the firewall.

To avoid replacement, a previous owner bypassed the leaking heater core by rerouting the heater hoses. Remove the hose clamps to allow the core to come out.

With both the heater and evaporator cases loosened from the firewall, access the heater core by removing the four bolts on the cover of the evaporator case.

Carefully pry up the cover to access the core.

When the cover is removed, the heater core is finally visible.

Remove the core by pulling it up and out of the evaporator case. If the core is still connected to the heater hoses, remove them. In this case, the core had long been bypassed by cutting the two hoses off the core and joining them together with a nylon fitting and other clamps. Removing the old hose clamps allows core removal. Once that is done, remove the core as shown here.

This is the evaporator case with the heater core removed.

Thoroughly clean and vacuum the evaporator case before installing the new heater core.

The new heater core looks like this. The cost is the least worrisome part of the project as the labor to install the core is about 95 percent of the job.

With the evaporator case cleaned, the new core is set into place. Once the core is in position, put everything back together. It's basically a reversal of the disassembly.

Once the heater core is installed and the evaporator case is back in position, the A/C lines are reconnected in preparation for recharging the system. The lower line presses and snaps back into place onto the fitting as shown.

The hose fitting from the A/C accumulator is reinstalled as shown. This can be done with the correct-sized wrench.

With everything back together, the core must be reconnected. This involves hooking up the existing hoses to the core or installing new ones. In our car, one of the hoses used when the core was bypassed was long enough to reach to the core and is reconnected, shown here.

The other hose used to bypass the core wasn't quite long enough, so we replaced it with part of the blue police hose kit already installed. It is trimmed to length and installed with new clamps. While most of what we show doesn't cover reassembly, you can see that it's a big job. But after getting this clean '88 LX 5.0 convertible back together, it is worth it to have heat again.