Removed (broke) my windshield out to repair some rust at the corner where the A pillar meets the top of the cab. Have rust-through on one side.

This is a 1977 F-150. There is a pliable filler material that was used from the factory to smooth out the transition from the A pillar to the cab roof around where the windshield seals. I had to remove the filler to treat the rust.

1. With what should I fill the rust-through?
2. What type of filler must I use to replace the factory stuff? Is fiberglass filler OK or does it need to be something more pliable?

If fiberglass filler will work, I'll fill the hole and smooth out the transition in one step with that.

ps. i'm not upset about the windshield, it was already in bad shape

 

the material is probably butyl rubber sealant. They sell it in caulk tubes, or ribbon. Is it black and kinda gooey?
The best way would be to grind away where there is rust, clean rust out of pits and weld up holes in the metal if they are there. If really bad, then a replacement patch should be welded in. Epoxy prime the metal. The only way to get a lasting repair. If you just shove fiberglass or bodyfiller into holes, I don't give the repair too long of a life.

 

Ditto what he said.

 

The only thing I would add to whats been said so far is you may want to consider using a metal panel adhesive to replace the metal that was removed instead of welding. These metal panel epoxy adhesive are a good alternative to welding and makes even more sense if you do not own a welder and not having all that heat is a good thing so you don't hurt the paint on the surrounding metal.

 

After wire brushing all the loose rust I'm left with a hole (more like a slot) that is about 1" long and 3/16" wide so it's fairly small. That's why I was considering only filler. Any holes bigger than that I've welded in patches.

Kenseth, actually there are two materials. One is light colored, looks like body filler, but is pliable. It was painted over from the factory. The other is a black gooey substance that was on the outside of the paint (placed there to help seal the windshield?) Anyhow, it's the light-toned stuff I need to replace first. Is body filler ok for that or is that area (where A pillar meets the roof) prone to flexing? I can take a picture if needed.

Also, once I've brushed away the rust, will a rust treatment spray help keep it from returning or is that a waste of money?

Appreciate the advice, guys.

 

Here's the area I'm talking about. The rust-through is about 1" long. The picture makes it look worse than it really is.

 

If you decide to go with a filler I would use a product called "All-Metal" I believe instead of a fiberglass filler and I would also treat the area with a rust converter prior to the repair. There are many them out there the one I'm familiar w/ is called "Oxi-Solve" sold by Eastwood.

 

I have no idea what the light colored stuff would be, where was the light colored stuff located, around the flange where the window sits, or ??? All I can think of would be sound deadener if it was inside the piller or some kind of rustproof coating if elsewhere. Don't really have a clue. Maybe a glass guy would know, most shops I've worked in left glass to the glass guys, and the old gasket style windows I haven't dealt with much, Most everything manufactured for quite a few years now are urethaned in windshields.

 

Re reading your original post, it believe that would be seam sealer. Seam sealer would be used where two panels meet and are spot welded together to prevent moisture from entering the seam between the two pieces. A 2k seam sealer would be better to use then a 1k type, but require a special gun to apply. If the seam is seen, I wouldn't use filler. Unless the seam is welded solid, it will crack as the piece can be allowed to move. If you do decide to use a filler, a fiberglass type filler or aluminum filled such as all metal would be better to use instead of plastic filler, and once that is down, any pinholes ect in that could be filled in by skimming on some plastic filler. If the seam is welded solid, go ahead and use filler if you wish. Plastic filler will absorb moisture, so If you think there may be any voids in the weld where water can reach, a fiberglass filler down first would be a good idea.

 

Seam sealer would make the most sense. The area won't be seen as it will be behind the windshield gasket. I was concerned that if I used regular body filler it might crack out.

Having seen the picture, would you still weld up the rust-through or would fiberglass filler be ok there? Again, many thanks for the advice...

 

I have read the post and basically had the same problems on the 88 I have. I have tried fillers and seam sealers and they work for a few years but rust does come back. Last summer I had to replace the windshield , so I decided to weld the repair with my new mig welder. It was a little tricky as the rust area is always bigger as you know and the metal seems thinner as it is stretched when stamped to make curves . Eventually with spot welding I built up the area so I could grind the new applied metal to the original shape. I guess it depends on how long you want to keep the vehicle and how much time you want to invest. I believe that you never get rid of rust completely but control it. I took some pictures and I will post in my gallery.
Roger

 

I decided to grind and brush away all the rust then treat it with a rust-converting paint. Fortunately I could also treat the backside of the rust-through from the inside of the cab through the hole where the visors mount. Next I used a fiberglass filler to fill the void and smooth out where the seam sealer had been. Fortunately most of that area is going to be covered by the windshield gasket so it doesn't have to be perfect, just good enough to seal. If/when it cracks out, then I'll have a problem. However, this truck won't be a daily driver (it'll be lucky to see 2000 miles per year) so maybe it'll last a while. If not I guess I'll be doing some more welding.

 

It sounds like you are doing a a pretty good job. It should last a long time .Being that high up it doesnt accumulate that much water if any. These vehicles are getting old so you have to expect this sort of thing. The fact that you have removed the windshield to do the work helps tremendously as far as how long it will hold.

 

You may want to try brazing the hole with a torch and a bronze rod. The area you are doing is small and since it's up on the edge of a very rigid area you won't have any warpage to worry about.
I've done this on similar areas with some holes and even pin holes areas. With good torch control you can do a decent job. Mig welding will bolw right through the thinner rusted metal leaving you a bigger hole (two or three times the original) to deal with.
Yes, that stuff is seam sealer. It also runs the length of the rain gutter above the door and covers the weld of the roof panel to the A pillar.
The windshield molding will definitely cover your work. Whatever you decide, hitting it from the inside is a great idea. Drop your headliner and do the entire length of the windshield with rustconverter and then an oil rust inhibitor like "rust check" will help it disperse moisture and make it last longer. This area is very typical for rust on 73-79 trucks as the windshield moulding traps water. If you want to see an extreme case and my repair adventure check my gallery.

good luck

Frank

 

Making bigger holes was my biggest fear. My other welding ummmm "repairs" didn't turn out as good as I'd like but with the proper application of some body filler they turned out OK. But that's why I decided to use fiberglass filler. Hopefully it'll hold together. I didn't consider brazing it. If I have to fix it again...

Looks like you did a great job on yours. You must have more patience than me!