I'm working on a 2003 Ford E450 Collins bus
I took out the windows thinking it would be a good idea to clean them out and reseal as others have suggested. Upon doing that, I saw that there are black rubber or foam tubes (I can't exactly tell what the material is -- I'd say more similar to rubber than foam) that are actually creating the seal for the windows. They are in pretty good shape. There's also a bit of silicone-type sealant on the bottom. Seems there was a very small amount of leakage from some judging by rust, but not much.
The unusual thing is (at least I haven't seen this shown in any video or forum about this) that the bottom tube is lifting the window up about 1/3" or more. I removed the tube from one window, put the window back on dry as a test, and there is a gap at the top (not to mention the window seals on the front face of the top aluminum bar, not the top bar of the aluminum itself, meaning it needs to go up even higher than just the gap). I suspect one or two lines of butyl tape will not give it that much lift.
The most simple solution that will work is appealing, but that said I live in the PNW so a good seal is important. One idea was to just to keep the black tubes in place, and get that 3m auto sealant and seal up from the exterior and interior around the tubes very well. Will that sort of sealant stick to the tubes and create a seal?
Perhaps something like this
could be used to replace the black tubes entirely, then sealant applied to both sides? There are some sections that need to be replaced either way from deterioration-- so I will need some sort of substitute for those sections even if I don't replace tubes on all of the windows.