Cab corner question: Prevention not Replacement

[Kenfuzed]

I've been searching the forum for days without any leads. There are plenty of posts about replacing cab corners due to rust but what I really want to know is, how does water get into the corners in the first place?

I'm fortunate that my truck is practically rust free, however after this last rain Sunday I noticed the back corners of the cab behind the seat are damp inside. The truck doors were closed during the rain and was not driven, only sat in my driveway. I don't see anything leaking around the rear window and the door seals appear solid, but they are not new either.

Before this becomes a rust problem I want to identify how water normally makes its way into the corners and what can be done to stop it.

[Kenfuzed]

It's been pouring rain here all day and all I can think about is water pooling up inside the corners of my old truck. Anyone have any ideas??? I spent another few hours Googling but there is nothing other than how to replace rusted corners or sites selling the parts to do the work.

[chevy_mike]

Couple ways I could think of is around the gas filler gasket/neck. Another way could be the inner and outer seems of the body, where the rear window gasket goes. Water could wick it's way and then run down the inner panel to the corners. This would be likely if you have an older gasket that doesn't quite seal as well as it did. Another spot could be the 2 rubber stops on the edge of the cab door frame, at the rear of the door. Water would be running on the outside of the door gaskets but these are outside of the gasket. If missing or not a good seal, it could be there.

Just some ideas.

[AcampoDave]

Mine does that too. Not much, but it does. I cleaned and painted those pockets and drilled a drain hole. Works great. I have since re-sealed my roof gutters. Maybe it got in around there and ran down between the cab panels.

[Ratpin]

Most of the rust through in pocketed areas is from collected sediment holding in moisture causing the metal to be constantly attacked. If you have some surface rust only just wire brush it as best you can, use an acid to convert it, rinse it and let it dry completely and the apply an amber rust preventative coating (cavity wax) to those areas. This will help keep the water off of the metal.

[Kenfuzed]

Thanks good places for me to check. I don't think it is the gas filler seal since water is showing up on both the passenger and drivers side equally. Though I suppose the water could run along any edge of the tank and drip off both corners.

The back window seal is less than a year old and appears solid.

I didn't think of the roof gutter seal and didn't realize there was a path for water to travel if that was cracked. The calk (for lack of a better term) that lies in the roof gutter appears quite old but I didn't know that kept water out of the inside but rather was just there to protect the gutter from standing water. That calking is not missing in any areas but could have tiny cracks from age. If the roof gutter seal were bad would that allow water to make it's way into those back corners? And if so, where else could water be reaching from that same source?

[Kenfuzed]

Originally Posted by Ratpin

Most of the rust through in pocketed areas is from collected sediment holding in moisture causing the metal to be constantly attacked. If you have some surface rust only just wire brush it as best you can, use an acid to convert it, rinse it and let it dry completely and the apply an amber rust preventative coating (cavity wax) to those areas. This will help keep the water off of the metal.

Thanks Ratpin, the major concern is the water that is currently getting into those rear corners. There is some dirt or sediment collected there but no rust (yet). I had thought of drilling some holes but would also like to attack the source of the water so it is not reaching that point in the first place.

[AcampoDave]

There is a seam in the gutter. The roof dome is spot welded to the lower structure and the sealant keeps the seam dry. If water enters the seam it can begin to rot the area above the windshield and the A pillars. From there it can and will find its way to the floor. I have seen several trucks with severe cab rot due to the roof seal being neglected. In fact I am currently in the process of sending a roof to another member in Pennsylvania . The roof dome on his truck is rotted out. Be sure your weep holes are open in your gutter, and by all means clean it up and re-seal it. I sealed mine with an epoxy resin (designed to bond to metal) in a dual syringe applicator from Orchard Supply. It's holding up well but there are also products made specifically for the job by 3M and the like.

[Ratpin]

Originally Posted by AcampoDave

There is a seam in the gutter. The roof dome is spot welded to the lower structure and the sealant keeps the seam dry. If water enters the seam it can begin to rot the area above the windshield and the A pillars. From there it can and will find its way to the floor. I have seen several trucks with severe cab rot due to the roof seal being neglected. In fact I am currently in the process of sending a roof to another member in Pennsylvania . The roof dome on his truck is rotted out. Be sure your weep holes are open in your gutter, and by all means clean it up and re-seal it. I sealed mine with an epoxy resin (designed to bond to metal) in a dual syringe applicator from Orchard Supply. It's holding up well but there are also products made specifically for the job by 3M and the like.

My suburban has fallen victim to a roof seam leak. I recently removed the door seals from the cab and noticed some pretty severe metal deterioration near the dash to the pinch weld that the seal rides on. Last week when I had it out in the rain and water was collected in the rain gutter, I could see water running out from inside the pinch weld near the dash. So basically water was coming in at the roof pinch weld, running down inside the a-pillar and exiting out the pinch weld near the dash and this is what caused the inner part of that pinch weld to rot away. Another thing on a long list of things to fix.

[Kenfuzed]

Originally Posted by AcampoDave

There is a seam in the gutter. The roof dome is spot welded to the lower structure and the sealant keeps the seam dry. If water enters the seam it can begin to rot the area above the windshield and the A pillars. From there it can and will find its way to the floor. I have seen several trucks with severe cab rot due to the roof seal being neglected. In fact I am currently in the process of sending a roof to another member in Pennsylvania . The roof dome on his truck is rotted out. Be sure your weep holes are open in your gutter, and by all means clean it up and re-seal it. I sealed mine with an epoxy resin (designed to bond to metal) in a dual syringe applicator from Orchard Supply. It's holding up well but there are also products made specifically for the job by 3M and the like.

Great info, some more things for me to check when the rain stops. Previously looking over the entire gutter I didn't see anything that looks like weep holes. The entire gutter all the way around has what looks like an epoxy sealant or calking and no clear place to drain so a PO probably sealed it all. I stumbled upon some other threads describing where the holes should be so I'll need to clear those so water isn't pooling and seeping through any cracks back into the cab.

BTW, there are no signs of any rust or rot around the windshield or pillars so fingers crossed that the problem hasn't been around long enough to cause irreversible damage.