Ever since I had Toyota pickup trucks.. water has always came in the driver side ends up laying on the floorboards... I've never been able to isolate how it's getting in... Does anybody know how it's getting in? through the cow or through the windshield gasket? seems to be a common problem in all the older Toyota pickup trucks.

New to the forums thank you!

Frank in VA.

 

The seam where the bottom of the cowl hits the firewall and inner fender seemed like likely culprits when I was having that problem, as did the windshield. Uploading some bad photos showing where I globbed sealant. Also resealed the windshield at the same time, but I'm pretty sure in my case it was all of the above. No leaks now. Of course I also had to have a new floorboard welded in after 20 years of ignoring the problem.

All along this seam, there's black sealant you can barely see below the white stuff.

This is on the inside, maybe use the fuseblock for reference. You can just barely make out black sealant surrounded by orange paint in the background. Seemed to be an intrusion spot, was all rusted up. Spent a very sucky few hours on my back treating the area.

 

See openings right where I said...thanks! See pics...

 

You...)

 

Also inspect your roof rain gutter seal. If it's compromised it would let water into the roof. It then wicks on inner pinch weld of A-pillar and drips down.
On a dry day. Start low. Spray on the seams mentioned above, Then the A-pillar gutter, then around the windshield, then on the rain gutter. See which allows water in.

The windshield trim does not do anything to keep water out it is superficial. In fact it traps water, worse yet saltwater from equipment, prevents drying and hastens rust. What really seals and holds windshield on is a substantial bead of urethane adhesive. That is so strong that stock adhesive is unlikely to fail. Pinchweld where windshield attaches to is more likely to rust and fail than the urethane adhesive.

 

Had a driver side water leak 20 years ago and used silicone sealant in the same seam as shown in the blue painted interior picture with the creamed colored sealant added. Never an issue again.