I know there have been multiple threads on here about windshield leaking water that drips down the dash at the corners, so I will apologize up front for bringing this subject up again.

I know that back in the 80s when I was driving my truck to HS and college on a daily basis, every single time it rained, water would drip in the cab at the corners. I never removed the windshield back then, but I did try everything I could to try and stop it. I pulled the rubber back and tried to pump silicon in the corners. I tried all sorts of glue and rubber cement. Nothing ever worked for me.

As I’ve been working on my cab with it completely stripped, I noticed something that caught my eye a few days ago.

On the seam where the front on the cab joins the back, the seam line forms the lip that the windshield rubber fits in and holds the windshield in place. This seam is spot welded every few inches, it is not a solid weld.

Passenger’s corner. Not the best pic, but there is a gap there.



Driver’s corner



Please overlook the sanding dust, but I’m just curious if these areas allow the wind to force the water in and allow it to leak at the gap in those locations. Also the fact that the surface isn’t smooth and allows the rubber to pull away over time.

Have any of y’all clamped these joints together and added more spot welds? Or filled it with seam sealer prior to priming and painting it? And stopped your leaks?

Or is it as simple as making sure the right sealing compound is used

Just wondering... or maybe I’m just overthinking it.

Thanks,

 

Are you sure it's the windshield leaking? can you see water running down the face of the dash? If not, it's likely the cowl vent leaking. Water runs down the back side of the dash and drips off the ends. My F-1 leaks this way even when I wash it.

Still wouldn't hurt to seal up those seams.

 

Mine leaked at the corners. Had a new windshield rubber but it didn't matter. I had a glass shop run a bead of clear sealer around the windshield rubber and that fixed it.

 

Do these truck leak from every where then?? I've just bought all the sound deadening and new carpets!! Living in the UK the weather is consistent. If it's not raining......it's about to...


So is there a thread already for "leak proofing" the cab on rebuild? I'm about to start paint before I put all the seals and windows in.

 

They are supposed to leak in the corners. Somewhere on this forum there is at least one thread that discusses and shows the OE holes in the corner. These holes may have been an after thought, a running engineering or manufacturing change. I guess rusting out the floors was preferable to the windshield frame.

As I remember it wasn't every plant nor every model year. Regardless the windshield frame is mis-designed so that water collects at the corners. Below are the instructions for windshield installation and note that they recommend the use of cellulose tape and rubber cement. These days butyl rubber that doesn't harden is used by installers instead to seal leaks. There is an air gun or caulking gun tube with a thin nozzle used to apply sealant between the body and the rubber weather strip. If the windshield is seated properly and there are no bends or high spots in the metal flange you should not need butyl sealer between the glass and the windshield, but I have seen it applied there as a bandaid.

Also never use silicone sealer or urethane on these types of windshields. Those products are designed for use on modern windshields that have no rubber rather use urethane to hold the windshield in place and add structure to the body.