Jim Smart
August 1, 2000
Photos By: The Mustang Monthly Archives

Step By Step

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Ford's factory assembly manuals and shop manuals indicate the proper way to install a windshield or backlite. You need to use a thin bead of butyl seal (nonhardened, gooey, petroleum-based caulk) in the inner and outer grooves of the gaskets. All window-trim clips should also receive a dose of this sealer, as shown in the illustration. This handles the foundation of your installation. Once the glass is installed and seated, pump as much sealer between the gasket and the body as you dare, then install the trim.
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Fastback backlites are vulnerable to leakage, so it's the same drill here. Use a thin bead of sealer in the grooves and at the molding clips. Molding clips are avenues for leakage if left unsealed. Once the window is seated, fill the perimeter between the gasket and the body with sealer, then install the molding.
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Although '65-'66 Mustangs bare similarity to the '67-'68s, they're not the same when it comes to soft parts. Doors for the '65-'66 break down like this: Vent-window gasket (A), vent-window seal (B), window channel assembly (C), outer window felt (D), inner window felt (E), door weatherstrip (F), and window grommet (G).
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For the '67-'68, there are fewer soft parts. Vent-window gasket (A), window channel (B), door leading-edge seal (C), outer window slipper (D), inner window felt (E), door weatherstrip (F), and window grommet (G).
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Anatomy of a door. Window felts inside and out (A/B) for the '65-'66. Window rubber out (A) and felt (B) inside for the '67-'68. Window channels (C) stop the rattles. They're riveted in for the '65-'66 and screwed in for the '67-'68. Door weatherstrips (D) are retained with 3M Super Weatherstrip Adhesive for the '65-'68. Door grommets (E) are retained with sheetmetal screws for the '65-'68.
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Quarter windows are similar in construction for the '65-'68. For the '65-'66, we have the quarter window leading-edge strip (A), window gasket (B), outer window felt (C), inner window felt (D), and the window grommet (E). The outer window felt is retained with clips. The inner felt is retained with staples to the quarter trim panel inside. The leading-edge strip slides into place and is retained with a single machine screw at the bottom.
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For the '67-'68, quarter window changes were simple. Instead of an outer window felt, Ford went to an outer rubber slipper. Soft parts work out like this: leading-edge strip (A), window gasket (B), outer rubber slipper (C), inner felt (D), and the window grommet (E).
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Window slippers and felts are easy to understand and install. Outer window slippers and felts are retained with one-time-use clips. Inner felts are retained with one-time-use clips, except for the rear quarter windows--where they are stapled.
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Windshield and backlite gaskets come from Mustangs Plus as shown. Although these gaskets are still available from Ford, Mustangs Plus tells us reproductions are of a better quality and fit.
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Thoroughly examine your gasket prior to installation to determine proper fit and positioning.
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Weatherstrips and seals are installed using 3M's Super Weatherstrip Adhesive. Apply the adhesive modestly to both surfaces and allow it to tack off.
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Apply one more thin film on one surface to react to the adhesive, then install the strip. Make sure you don't use too much.
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Window grommets are installed with screws. These guys seal the weather out where the doors meet the body at the windows.
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Hood trailing edges have seals at the cowl to prevent underhood contaminates from getting on the windshield. For the '65-'66, this seal is retained with two 90 degree metal brackets and screws. For the '67-'68, this seal is an air-cell foam affair with nylon retainers.
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Door perimeter weatherstripping can be a real pain in the neck because it does not stay put as the original equipment did: you tuck it into place and it falls out or it pops out when the door is opened. Suggestion? Use 3M's Super Weatherstrip adhesive on both the weatherstrip back and the stainless frame for best results, then tuck it in place with permanent results.

Such soft parts as weatherstripping, window channels, door rubbers and grommets, windshield and backlite gaskets, trunk lid seals, and hood weatherstrips are items we can't imagine doing without. Yet if you look at most Mustangs on the road today, you'll notice that most of them need new soft parts. Slam their doors and the windows rattle. Open the decklid and you'll find chipped paint because the seal has hardened. A wash job makes the carpet soggy because the door weatherstrips or windshield/backlite gaskets have become brittle and ineffective.

Our point? Soft parts are more important than you realize. What's more, proper installation is just as important as the need for replacement. We want to show you where these soft parts are and how to replace them with the best results possible. We'll show you with photos and illustrations that will give you insight into all of your Mustang's important soft parts.

Windshields and Backlites
Certainly, a frustrating point for most of us who restore Mustangs are leaking windshields and backlites. We've visited with a lot of auto glass installation professionals, and no two have the same routine for leakproof windshield and backlite installation. So we looked to Father Ford on this one because we want to understand how Ford managed a leakproof installation to begin with.

The Right Stuff
Whenever you're installing classic Mustang window glass, it's important to remember to use the correct sealer. Because classic Mustangs have window grommets or gaskets, they use a different type of sealer from the sealer used on late-models. Because gasket-type windshields and backlites are becoming very old news, a lot of windshield shops don't carry butyl sealers anymore. They use 3M's Windo-Weld--sometimes in error--on classic Mustang windshields. Problem is, Windo-Weld is an adhesive and is used for gluing glue-in windshields into place, so it has no place on gasket-type windshields. Windshield adhesives make the windshield virtually impossible to remove, should it ever need replacement in the future.

Remember, always use a butyl (rubber/petroleum-based) flexible sealer on your classic Mustang windshields and backlites. If your windshield shop suggests gluing in your windshield instead of using the rubber gasket, find another windshield shop.

Felts, Rubbers, and Channels
Classic Mustangs used two basic types of soft parts for doors and windows: molded rubber and felt. Between the door and the body, Ford used molded air-foam rubber weatherstripping. This weatherstrip is retained with 3M Super Weatherstrip Adhesive, available from most autobody paint and supply stores. Run a thin film of this adhesive on the weatherstrip and on the body. Allow it to skin over for 20-30 minutes, then lay down a thin film of this sealer again on the body, and install the weatherstrip. The adhesion will be permanent.

Window channels guide the window up and down in the track. In order to access the channels, you must remove the door panel. For the '65-'66 model years, the channel and window track are one. For the '67-'68, the window channel is installed in the steel window track. In any case, your objective should be a smooth operation. For the '65-'66, the window channel assembly slips into the vent-window frame, with the grommet at the top held in place with a single rivet. For the '67-'68, the soft channel is retained at the top of the track with a single-sheet metal screw.

Window felts and slippers are retained with clips externally and internally, except at the rear quarter windows--where they're retained internally with staples. The greatest challenge is to ensure the window does not remove the slippers and/or felts during roll down. This is where proper window adjustment is vital.

Other Seals
Both the hood and the decklid have seals as well. Decklid seals should be installed using 3M's Super Weatherstrip Adhesive as explained earlier. The seal's mouth (groove) should be pointed inward, never outward. It should be attached to the lid, not the body. The seal's end gap should always be positioned at the trunk lock, never at the backlite. These suggestions are based on experience and knowing how the factory did it to begin with.