Try Ailene's Tacky Glue. Use a syringe to inject 1 inch diameter spots between the fabric and backing. The glue has enough substance that it penetrates the rotting foam. You'll need to use a 2 x 4 and a cardboard pad to hold the headliner in places as glue dries. It's held up for a year in our '90 745. The headliner looks like a dalmatian, but it doesn't sag. We used upholstery buttons in my mother in law's '88 744 at the rear of the headliner. That car has a much thicker headliner than the '90, but the buttons have held up just as well.


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D '90 745T 216k, '88 744GLE 128k, '96 328i, '73 911T 100k+