Without a nice roof panel, to use as a replacement, the only solution is to fit in sheet metal to close up the hole. Just to make things a little more challenging, the instalation of the sun roof, caused a fair amount of distortion and stretching of the roof panel at the rear corners. All I can do is shrink, stretch, pick and dolly as required.
I’ve used a salvaged roof panel out of a 1980’s Ford Pickup to fill in the opening left by the sun roof. It does a pretty good job of matching the curvature of the XJ-S roof line. Simplest solution for fitting, is to lay the panel over the opening, position for the best fit, and trace out the opening onto the panel through the opening.
For some undetermined reason that eludes me now, I thought I should do a butt weld, rather than using the bead roller and flanging the edge to create an easy to weld overlap that would give a nice neat appearance on the inside (what the hell was I thinking)
Then, to add a little icing on the cake, get some dufus to cut it out, and end up on the wrong side of the line creating a nice little gap to close up.. Oh Wait.. That dufus would be me! Well, we all have our bad days..
(That’s my story and I’m sticking to it)
No sense whining about it.. Can’t be undone. Get the panel fitted into position and held by panel clamps ready for welding. You’ll notice the 1/16″ welding rod, laid into the gap between the panel and the roof where required to give something to weld to. (grrr)
I only have one set of hands, and this job can easily use more. So, I have a telescopic jack that I use to support the joint from the interior side, while I weld on the top side. I’ve placed a slab of aluminium on top of the jack pad to act as a heat sink to draw off heat from welding to reduce shrinking and warping. Copper is the material of choice, but, aluminium is readily available for most people and makes a reasonable substitute. This can also act as a dolly and support for the weld area. This greatly assists (especially in those gap areas) to hold the material in place.
Remember, ALL heating and welding processes are in fact SHRINKING processes. The less heat you apply, the less shrinking and warping will occur.
Preferably using a MIG, get the panel spot welded into position on all sides. These should be VERY quick spots, taking only about a second, creating a weld around 1/8 inch. Get the sides, and the corners. Then, continue moving around the panel, splitting the distance between any two other spot welds. No two spot welds should be performed in close proximity or adjacent to one another. Always move away to a different location after each spot weld. You do this to minimize the heat on the metal, to keep warping under control.
Lots of grinding, lots of dolly work. Then, re-weld the sections that have been broken with the stress that has been placed on them. Stretch, dolly, shrink, dolly, and VOILA you have a normal roof again. This is NOT something for the faint of heart. It’s a slow process, and frankly, should be avoided if possible.