fast cars said:
There must be a cost effective way of getting the lining to stick back up to the roof as opposed to replacement, common sense tells me application of a spray adhesive?? Any ideas or stories of fixes?
Realistically, I don't believe spray adhesive will be an effective solution. Whilst I have no doubt it would fix the fabric back up and hold it on to the headlining biscuit successfully, the fabric is thin and the glue would show through to the other side - both in visible colour variations on the fabric and in variations in texture. This was my experience when I tried it to see if it would work.
For a 'factory look' job, I suspect the headliner biscuit will have to be recovered. It is not an easy job, but the headliner is removable from the passenger's door with the door card removed and the centre console out.
Once out, you will find the headliner has dropped not because the glue has failed, but because the foam has rotted. The fabric can be pulled off the fibreglass reinforced 'biscuit' easily, leaving a dark grey foam residue. This can be brushed off the headliner - I found an old toothbrush did the job well.
New foam based fabric can then be glued on to the biscuit. It is widely available, but I found I was unable to get an exact colour match anywhere, so if your car has a sunroof, you will also have to recover that. If you need to do this, be very careful with the thickness of the foam. Anything above 3mm you will struggle with and even at 3mm the fabric will need to be pulled very tight in order that it does not rouche up when opened.
I eventually decided to get a new headliner from Jaguar (for my XJ40) and to cannibalise the fabric from an old headliner for the sunroof panel, since these were not available. The fabric without its foam layer is very thin - far too thin to be used on the sunroof panel. In order to raise it to the necessary fabric weight, I bonded a heavy fusible interlining fabric to it with an iron. This was highly effective and looks a factory job.
Seeing this did make me wonder whether I could have done this for the whole headliner - bonding several layers of interlining fabric to the original headliner (I'm thinking two or three layers would be enough) then spray glue the whole thing to the biscuit, bypassing the need for the foam component.
Providing you could bond the interlining fabric over that large an area without bubbles, I do believe this would be effective. Even so, you would still need to remove the headliner from the car.
As an aside, the headliner I bought from Jaguar has cut outs for alarm sensors - which my car did not have. Frustratingly, I have found these so far, impossible to obtain!! So even with a brand new genuine headliner I'm no still further ahead!!!