I have a Ford f150 98 and the rear window has been leaking for some while now. When it leaks, it runs down the back glass, but lately I noticed that it also fills my dome light as well. How do I remove the back glass to check/reseal it, or could it be my 3rd brake light leaking?

 

Reg cab? If your dome light is right next to the 3rd brake light that would be my guess. Other than that I don't see how it could get there without seeing significant damage to your headliner as well.

 

does it have weather stripping? if so replace it. if not, put a little bit of silicone around it, but do a half decent job or otherwise it will show.

 

Car glass includes windscreens, side and rear windows, and glass panel roofs on a vehicle. Side windows can be either fixed or be raised and lowered by depressing a button (power window) or switch or using a hand-turned crank. The power moon roof, a transparent, retractable sunroof, may be considered as an extension of the power window concept. Some vehicles include sun blinds for rear and rear side windows.

 

I had this problem with my old 2000 F-150, and it was the brake light. Fixed it with silicone. I think if i'm not mistaken, a lot of those f-150s had that problem.