Jim Smart
January 2, 2016

Rubber gasket windshields and backlites have always been problematic in classic Mustangs. We can tell you with great certainty Mustangs suffered from windshield and backlite leakage right off the assembly line, hence soggy carpets and floor pan rust. Leaking cowl vents were another source of wet carpet and rotting floors. If it passed the water test at the assembly plant (and even if it didn’t) it was shipped to the dealer.

There are a number of approaches to windshield and backlite installation and we’ve seen them all. Chris Ingrassia of Mustang Restorations in Chicago, Illinois tells us only one method works well most of the time—sealer between the glass and rubber, and sealer around the outside perimeter once glass and gasket are installed. You must use a pliable non-hardening sealer, 3M’s 08509 Auto Bedding & Glazing Compound, which remains pliable and seals very well. Never use a urethane sealer/adhesive because it will bond windshield, gasket, and body into one and you will have a very tough time replacing the windshield later on.

There are several approaches to windshield replacement but only one really works. Use 3M’s 08509 between glass and the rubber, install the windshield, and seal the perimeter around the rubber gasket. Install the stainless trim.

We’ve seen glass replacement shops and enthusiasts apply tons of sealer to where there’s a huge mess to clean up. This isn’t necessary. You want a thin bead of sealer in the groove between glass and rubber. Once the windshield is bedded in the vehicle all you need then is sealer between the rubber gasket and frame. Inject sealer deep between the rubber gasket and frame and do it in phases. Let the first application settle, then, apply the second layer. Don’t overdo it. Then install the stainless trim.

Isn’t it nice to have dry feet?