Under drip rail rust repair

[mm1077]

My new truck is going to be a driver but I’m sorting out some of the worst rust issues in the cab right now. The area of the door jam directly under the drip rails are rusted through and I’m wondering if I can safely cut out a small section of the roof to access and weld in a new piece from above or if I can just patch in a section from underneath the the drip rail? The drip rail seems to be pretty solid but ideally Id like to open it up and get some rust converter over all of it, but not if it’s going to turn into a major ordeal. The windshield channel, A pillars, etc aren’t showing any signs of major rust damage from the interior or exterior.
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[BigBird05]

That water had to be getting in there somehow. Check the windshield gasket.

[mm1077]

I found where the water was entering, there’s a really small hole in the corner of the windshield frame where the frame and A pillar meet

[BigBird05]

Thats good, Glad you found it.

[SkidmoreGarage]

I can't tell much from your pictures, but i went through some of this on mine. Mine leaked because the drip rail seam sealer had failed and cracked. It took a lot of effort to clean out the drip rail to clean metal. I also spot treated any surface rust on the interior frame, a pillar, and dash. You can see my build thread for more info. While you are this far into it, I'd recommend welding up the exterior seams in the windshield frame solid. It's the one thing I didn't do and water gets behind the gasket. I used seams sealer, but it's really the design that allows water to run behind the gasket and why I think most trucks have rust on the interior cab.

I wouldn't cut any good metal open to clean up the inside, as it likely wouldn't really solve the problem. You can use a rust encapsulator with a wand extension to get inside between the metal. Eastwood sells one, as well as 3m. To know if you have good metal, you'll need to start wire wheeling everything back. You might be surprised how many pin holes show up.