Water leaking into the cab

[Chapap]

I’m finding a bunch of posts for mechanical leaks, but can’t seem to narrow it down to rain leaking in. When I get a good rain, I get little puddles on the floor and my seatbelt is wet. The puddles don’t appear until I start driving and the truck gets jostled around. I can’t find a source anywhere. Windshield and door seals look fine, and I didn’t see any water marks behind any interior trim panels. I’ve taken off all interior trim, headliner, and carpet to do sound deadening and I didn’t notice any water issues. Are there any suspect spots to look?

The rear of the roof is pretty dinged up from the previous owner hauling boards and ladders propped up on the cab. there’s a little rust but not bad… nothing that looks close to leaking. There’s a seam on the rear-top corners of the cab that has a rust line. A little rust around the windshield. Outside-bottom door window seal is probably shot.

 

[Roert42]

Could sit in the truck with all the panels out while someone sprays the cab in different spots with the garden hose.

 

[tw205]

I’ve discover leaks in the cowl plenum. Trickles down the inside of the firewall. Also around windshield seal.

 

[ericbphoto]

Third brake light/cargo light is a common place