Have a 75 convertable and when it rains water drips behind the kick panels. I check the windshield frame and there are no rust holes. Does anyone know where the rain water could be coming from? Any help would be great, it's driving me nuts looking.
Check behind the seats. There is a rubber drain hose that runs from the vents on the rear deck through the car then outside to the upper part of the wheel well. They become plugged with debris rot and eventually leak. I've replaced them on both of the C3s I've owned.
Water leaks are not always easy to find. Water’s sneaky and will take the path of least resistance.
I have a lot of experience with air and water leak repair over the years.
I'll give you a quick run down to start diagnosing water leaks.
Remove panels/trim/carpet in the affected areas, run a stream of water all over the upper area of the car starting with roof on down. Saturate good. Remove nozzles on hose, use the naked end. Concentrate on gaps, seams and weatherstripped areas. Watch for drips and streams running inside.
It's easier with 2 people, one watering outside, one looking inside.
Water will sometimes take strange paths, not always the one you may imagine. The point of intrusion and area of gathering can be a surprising distance apart! And multiple entry points can be common. T-tops and convert tops are notorious for leaks.
Likely areas are weatherstrip crushes, tears, mounting and adhesion lifting. Along with any seams or joining points. Old cars like ours can have cracked/deteriorated body seam & glass caulking as well.
This could take you underhood to any firewall penetrations. HVAC case seals/seams, grommets, electrical connector passages, etc…
On a friends ’66 Chevelle resto, we found 22 abandoned open holes in the firewall alone! Probably from previous accessory mounting, wire runs, etc..
As mentioned above, the rear vents can be leakers also. I’ve seen them where everything looks good at a glance. But closer inspection showed deteriorated hose leaking at top connection, and along cracks at the back side.
Take nothing for granted when hunting leaks down.
Fixes can vary depending on the point of entry. You may need to plug holes, shim/replace/seal weatherstrip, seal fasteners and seams, adjust panels/glass, re-caulk, or in some extreme cases, fab deflectors. (there's a water deflector at the rear of the door sill plates. If this is broken or missing, it can allow entry along the inner rocker areas)
I use 3M strip body caulking (during diagnosis) to create temporary seals and deflectors. It can tip you off to entry points that need a more lasting (correct) permanent repair.
This can be a daunting task, but it's worth it to have a dry Vette and feet!
If it's behind the kick panels, then it's probably leaking as per the pic. The metal under the mount rusts from trapped water. Can't see it from inside, it's a double wall.
Convertibles also are bad about the upper windshield header and can run down the inside of the side windshield frame and into the kick area.
If it's on the pedals, then the wiper tray cowl seams leak.
As mentioned, use an open hose, but start at the bottom of the windshield and work your way up slowly.