Fix A Sagging Headliner
So your driving down the road with what looks like an open parachute attached to the interior roof of your car.
Well that open parachute would be your headliner material.
The reason for this misfortune is moisture and heat. These elements have been eating away at the foam backing of the material and the glue that holds the material to a molded fiberglass board that makes up your headliner. After a few years of abuse your headliner sags.
Now there are some fixes for small areas but for the full sag you will need to replace the headliner material.
For those small fixes you can use spray craft glue and spray a dry coat between the material and foam backing. Now what I mean by a dry coat is don't soak the material or it will bleed through and look like you blew your nose on your headliner, so light dry coats. Let the glue dry for a minute or two then lightly tap the material back up working from the start of the sag and working the material back up to the edge.
Now for the full sag there are a couple of options. You can take the car to an upholstery shop and get it replaced for around $150. Or you can do it yourself for around $30 to $40 and some time.
If you decide to do it yourself, first make sure there is a board behind the material, some cars stretch the material across the inside. You'll be able to tell.
You can purchase all you will need at a local upholstery supply dealer. If you don't know of one look in your local yellow pages. Take a small sample of material with you to match the color.
Remove all trim pieces holding the headliner board up, lights, seat belts, door post covers, ect. Remove the board, usually easier taking it out the passenger side, or the rear if a four door.
Now here's the critical part. All that old foam that is still on the fiberglass board needs to come off. The easiest way I've found is to use a steel brush. Scrub the foam off being careful not to tear the board up, it's real easy to mess up the board, it's made of fiberglass like the insulation in your attic.
Once you have the board clean lay your new material on the board and fold back half of it. Spray the board and the material with the spray glue you got from the supplier, I recommend 3m Super Trim Adhesive, it's seems to last longer and is a little stronger then most. Let the glue dry for about 5 to 10 minutes then, with clean hands, lay the material down smoothing it out as you work towards the edge. Now repeat the process for the other half.
Cut out with a razor blade from the back side the holes for the lights and visors. Usually an x will work, don't cut to much material away, leave about a 1/4" to 1/2" of material around the edges.
Let it dry for a while, usually a couple of hours is good.
Time for the reinstall, it usually helps to have someone help you hold it up while you attach the visors and lights. A little hint use a small screw driver or pick to find the holes for the visors.
Most vehicles this fix will work on but not all due to how they were installed from the factory. Some vehicles the board is glued in, so if this is the case I recommend you take it to a professional. Otherwise have fun doing your headliner and if you have any questions don't hesitate to contact me on how to fix a sagging headliner.