A lot of these trucks seem to leak in the drip rails and in the short seems between the drips rail and front and rear windshields. I think iy probably goes unnoticed for years. You can check by examining the seems closely and checking the sealer for cracks. Another thing to look st id the under side of the rails. Open the door and examine th eunder side of the rain gutter, if you see any surface rust or signs of water damange, its time to change the sealer. These leaks are commonly misdiagnosed as leaks from rear glass, door seal, window, extended cab window etc. In my case, the water was making its way to the floor and rotting out the cab. Here is a pictorial of the necessary steps.

Here is what my seam sealer looked like. It was cracked and leaking.




Use a drill with a wire brush to clean the old sealer out. This can damage paint so if you are concerned about that, you may have to use another method. I really don't think it is possible to clean it out properly without damaging some paint.




It needs to be cleaned out perfectly. The old nasty sealer is hard to get out of the tiny cracks, but you want new seal in there, so dont give up. I spent about an hour and a half with the drill.




Prep surface with mineral spirit wipe down.




I used Eastwood seam sealer for a standard caulk gun. Nothing is quite like seam sealer. It comes out thick and begins to skin immediatly. You can tell by the smell that it is serious stuff. make sure to press it into the seams.




Here is the gutter with new selant in.

 

Thanks for the pictorial!

I'd rep ya but it's not letting me.

But, I added this to the Sticky.

https://www.ford-trucks.com/forums/8...ml#post7434661

 

This is one of the #1 reasons why the cab corners and floorboard in the rear corners rust out on these trucks.

 

It is, indeed.
Rep's sent.

 

So does a leak from this seam leak down "inside" the wall, dripping through a hidden space between outer and inner walls? Where it can't be seen until it rusts from the inside out?

 

Right down inside the B pillar trim.

 

I had the same issue, and replaced mine as well.

 

My drip rails are horrible. I caulked them shut to prevent any water that might get into any cracks or such and go into the cab and rust out my cab corners any further.

I was thinking about shaving my drip rails one day, but when I think about all the rust on the inside of the cab, I think I'll be finding a new cab one day.

 

That's exactly what happens.

You will not notice the water pooling at the bottom of the "B" pillar especially if your truck has interior trim mouldings behind the seat.

The "A" pillar seams are prone as well and can mimic a windshield seal leak. (been there done that)

I used 3M All-Around Autobody Sealant #08500 with great success for this type of work. It's paintable and made to seal automotive seams. I've redone the drivers side and the seams on the bed that connected the bedsides to the floor that originally had sealant. It's held up great for over 7 years. It will even seal and fill small drill holes.

 

Thanks for the reps. This is sort of a fun job if you dont mind the mess that the wire wheel makes. I am working on a cowl reseal job now but haven't been taking pictures. I am basically wire brushing everything under the cowl cover, spraying with Rustoleum Rust Converting Primer, and then shooting everything with Rustoleum Professional Rubber Undercoating. While the cover is off i am sanding it down, smoothing some bondo, and foam brushing on some Rustoleum Stops Rust flat black. No I don't work for Rustoleum, but their products sure fit my project budget for this truck! I think the cowl reseal process has been pretty well covered already so I may not take any pics.

 

The outer window scrapes/seals/belt lines fall apart and let water pour into the door when it rains as well. The door can rust out, lock and window mechanisms fail and rust etc. I just installed new outer window seals a few weeks ago, it was crazy easy and made the truck seem a lot more like a legitimate vehicle to have rubber on the door and glass again, if that even makes any sense.

 

Mine doesn't even have window seals on either side. Door seals, yes. Vent window seals are good as well. But the roll down windows? You could just about order fast food and pass the bag through them gaps!

 

Some seam sealers are fine over bare metal but not all of them are so be sure to check before you use it. I'd invest in a spray can of etching primer and put a coat of that on the bare metal before I put new sealer on.

 

Great write-up!!

Shaving the rails is a huge pain. I did it on a cab a few years back and would not do it again. There's three sheets that meet at that point and one is fairly thick (for body metal). I've had people suggest doing that on my '81 and my response was "ain't gonna happen on this one".

 

Excellent write up to such a common problem! All my Fords had this problem!

I simply put clear silicone in all the seems for now, until i'm ready to paint the truck, then i'm going to do a proper job like in the pics just before painting.