Leak under dash?

[t44e6]

I haven't dug into it yet, but after hours of heavy rain I had a trickle of water from under the dash, drivers side left of steering column. I have the dash pad pulled out, not coming from the windshield seal...is it coming from where the firewall meets the cab under the cowl? The only reason it was obvious is because I have removed the floor mat to install sound insulation. Time permitting I will remove the insulation from around the column/pedal cluster and see what I see. Might be time to do some welding. It might be a good idea to yank the engine and seal it up, and look for any issues in the engine compartment. Looks vey clean from upstairs. Then I could clean up the wiring from the ESC delete and get a set of wires with loose distributor end terminals and get rid of the sloppy universal set. If I have the time.

 

[gmbellew]

I just had a leak. pretty sure the biggest culprit was the cowl drains. I would start by cleaning them. then see if you are still taking on water.

water leak into cab through floor vent over brake pedal

I have a suddenly new leak into the cab of the 1990 suburban. I washed the truck recently to knock off the road salt. after, I noticed some water on the driver floor. I just assumed that my 7yr old son directed some high pressure water into the door/body gap and it blew past the seal when he was...

www.gmsquarebody.com

 

[Zeeebull]

I've an 81 GMC that has a leak near the fuse box. I'm pretty sure it's coming in an unplugged screw hole above fuse box.
But now I think I'll look for these cowl drains mentioned earlier. I had the cowl off when I painted the truck last year, I cleaned under there a fair bit. Perhaps I missed something. I never noticed the drains.
Mine leaked since I got the truck a couple years ago.
Mine even leaks after I turn on the washer pump. Just a trickle.

 

[Ken B]

I have been working under dash and I too have or had a leak near fuse block. Haven't dug Into that side yet. Passengers side is bare

 

[gmbellew]

the cowl drains down to an outlet on each side behind the fender under the truck. I had to remove a plastic trim piece from each side to access them. see the thread I linked for more details.

 

[My78truck]

I haven't dug into it yet, but after hours of heavy rain I had a trickle of water from under the dash, drivers side left of steering column. I have the dash pad pulled out, not coming from the windshield seal...is it coming from where the firewall meets the cab under the cowl? The only reason it was obvious is because I have removed the floor mat to install sound insulation. Time permitting I will remove the insulation from around the column/pedal cluster and see what I see. Might be time to do some welding. It might be a good idea to yank the engine and seal it up, and look for any issues in the engine compartment. Looks vey clean from upstairs. Then I could clean up the wiring from the ESC delete and get a set of wires with loose distributor end terminals and get rid of the sloppy universal set. If I have the time.

Ruh-Roh......I had the same thing. The seam seal in the cowl was failing after 40+ years, was rusted through not only into th cab but at the top of the firewall. Cleaned it all up, and resealed the cowl area and up under the dash and fiberglass and sealed the firewall. Good luck!!

 

[t44e6]

I did it the other day. Everything came apart easily, no rust just failed sealant. Cleaned it up and used some brush on roofing sealant.

 

[My78truck]

Great minds think alike. Suck a PIA area to work on. I poured fiberglass resin into the seam then sprayed the entire cowl trough with rubberized undercoating.