Steve Baur
Former Editor, Modified Mustangs & Fords
December 1, 2009

Last month we tore into our resident '90 Mustang coupe and gutted the interior space to make way for a host of new components from Latemodel Restoration Supply and Corbeau. To provide a solid foundation to build on, we called Thermo-Tec for some of its sound and heat insulation material and proceeded to dampen the resonant characteristics of the Mustang's unibody chassis. This month we move ahead with this comprehensive interior restoration by prepping and painting all of the interior pieces, and then tackle the heater core and door-lock actuator installations.

Changing the heater core in your Fox Mustang is probably the worst mechanical job that you can perform on the car. It's long, tedious, and the chance of breaking the various plastic tabs, fasteners, and wiring harness plugs that are all intertwined within the dash is extremely high. But not having heat in your car sucks, and cold, muggy days will require you to keep a rag on hand to handle the defroster duties. If you happen to have a non-air conditioning car, the job is actually much easier, but I think the majority of 5.0L owners have to do it the hard way, and that's what we had to do.

We covered the dash removal last month; this month all we had to do was disconnect the A/C lines from the evaporator, and pull out the HVAC box that is bolted to the firewall. If you have to perform this job, pony up for a new A/C evaporator and do both at the same time. Failing heater cores have a tendency to fill up the bottom of the black box with coolant and erode the evaporator at the bottom. Pulling the dash is already a tedious and risky job, so make sure you only have to do it once.

We had just installed a new heater core and A/C evaporator last year, but we evidently bumped the heater core tubes a little too much during this year's engine changes-upon removing it, we found that the solder joint that welds the tube to the core had broken free. The leak was catastrophic, so we didn't give it time to saturate the evaporator in the case by leaving it connected. The engine probably would have run out of coolant in a short amount of time if we did. Latemodel provided us with a new heater core (PN LRS-18476A).

With that problem fixed, we moved to the new door-lock actuators. When we bought the coupe, the actuators were locked in one position, and we had to pull them out just so we could lock the car. Failing actuators are a common problem on older Fox Mustangs, so it's really no surprise, especially considering all of the other things that have been wrong with the car from the outset.

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That being said, Latemodel hooked us up with a new set of actuators (PN LRS-21842), which come with an assortment of rods, a new mounting bracket and a new rivet to install the bracket. The rivet is an industrial-sized piece that requires a larger-than-average rivet gun. They are rather hard to find unless you go to a tool store (the local Sears didn't have one). If you or your friends don't have one, fear not, as Latemodel sells these as well. Installation is simple: It will take you longer to remove the door panel than it will to install the new actuator.

That pretty much completed the mechanical modifications, so all we had to do was finish the sound-deadening installation and start painting the interior components. Thermo-Tec supplied us with its Suppressor and Sonic Mat insulation materials for our project, and we finished this part of the installation by covering the back-seat floor area. We also added some pieces to the upper C-pillar area, as well as the package tray. You could continue into the trunk, but there is already a factory material similar to the Super Sonic mat on the floor, so we called it good.

We spent a good 45-60 minutes per door as that took a lot of trimming and detail work, and we probably have two hours at the most into the floor and roof. We thought we'd be adding a ton of weight to the car with this, but the five rolls that we used equated to just 34 pounds. We can live with that, especially considering our notchback model is the lightest to begin with.

As with any paint job, the prep work is what determines the end result. Painting plastic and vinyl requires an extra measure of cleaning prior to painting if you hope to have your new finish stick well and last a while. Just think of all those years that you've been applying Armor All or some other protectant to the interior panels, and it's easy to understand why many color changes fail.

There are several different ways to clean the components, including rubbing alcohol, lacquer thinner, and a prep solvent of some sort. After we removed and disassembled all of the pieces to be painted, we gave each piece a liberal coat of purple cleaning fluid, and then scrubbed them with a stiff-bristled brush. We then hosed them off and proceeded to scrub them down again with laundry detergent and a bug scrubber that is commonly available at your local auto parts store. After the parts dried, we wiped them down with a bit of lacquer thinner, and then sprayed them with Latemodel Restoration Supply's interior lacquer paint (PN MET-FL33). If you're painting your armrest pads and the padded part of the dashboard, use LRS's Vinyl Prep/Cleaner (PN MET-VP383).

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LRS sent us six cans of the black lacquer, and we found needed about two more to complete the job. Compared to what you find at the local auto parts store, the LRS paint may seem a bit expensive, but the paint goes on extremely easy, and it has the perfect factory finish to make the panels look brand-new. We wouldn't do it any other way, and everyone that has seen the panels since we painted them have been equally impressed with the finished product.

While we were waiting for the paint to dry, we bolted on the optional Corbeau seat brackets to the GTSII seats that we will be using. Our brackets had seen better days, and the springs that connect both sides to the lever were broken.

Next month, we begin reinstalling all of the parts, and we'll be building new door panels using some products from Latemodel Restoration as well. See you then.

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