Q: What’s the best way to fix a sagging car headliner?
A: Those annoying cloth headliners always seem to eventually detach from the foam backing of a car’s ceiling. Mankind can put a man on the moon, but your car headliner is still going to fall off. To repair it you’ll need a can of quality spray adhesive, so don’t skimp and buy the cheapest stuff. Some products are actually specified as “Headliner and Fabric Adhesive.” Before applying the spray to the ceiling, you need to scrub or sand off the old powderized foam that caused the headliner to fall.
Use your fingers, a sanding pad or stiff-bristle brush to scrape away all this material, removing it until you reach intact material that won’t fall away like dust. Apply the spray adhesive to headliner backing, and to the backside of the fabric, and then wait 5-10 minutes before attaching the fabric.