Under-dash leaks!

[Hoss408]

Okay, I have a '73 that I am working on, currently have it stripped almost down to bare metal to coat the tub with Lizard Skin/Bedliner, new interior, etc. I am having a problem locating an apparent leak. When I had it on the road, anytime I was driving in heavy rain, I would start getting a stream of water from under the center of the dash (near the radio, ugh) and a second stream coming from under the dash on the right side, closer to the passenger door. I have been running hard doors that didn't seal well (switching to inserts/soft doors now) but it appears to be coming from below the dash, not around the doors. Took the dash mat off, and nothing was coming in above the dash and draining down, it was originating underneath. Don't see any huge holes in the firewall, although there are a few that need to be patched up, but relatively small ones. Any ideas on where the water could be coming in? And, more importantly, how to stop it? Thanks!

 

[thegreatjustino]

Rusty cowl?

 

[Hoss408]

looks to be in decent shape, but I'll dig into it and see for sure. Maybe coat it with some RTV under the hood to be sure...

 

[clarrance]

Check the ends of the cowl behind the fresh air vents, close to the top rear of the front fenders. The metal is bent in a way that the ends are open. They were sealed with seam sealer from the factory. I had a similar issue. Replaced the seam sealer and the flooding stopped.

 

[broncokak]

The windshiel hinge on my 76 would leak. I hunted all ofer and replaced all the seals under both air ducts and sealed up all the seams around the cowl. Just for giggles I put some clear sealent on the hing and the leak stopped!

 

[Dan's73]

Had the same issue on a '75 I had....like DirtDonk mentioned my leak was coming through a split in the seam sealer on the leading edge of my hard top, running through the windshield frame and out under the dash. Never thought about it until I had a chance to look down on my Bronco from a 3rd story window and saw a dark line along the seam where there shouldn't have been one. After sealing that up I had no more leaks.

 

[Rustytruck]

Ive seen cowl leaks so bad it leaked into the tube structure of the cowl. It then rusted through the bottom structure of the tube and leaked inside the cab. There is supposed to be a seal pinned across the back of the hood to direct water away from the top of the cowl and out by the fenders. Replace that seal if you dont have it.

 

[bstein]

Passengers side vent is to have a seal off the hood, so what keeps the water out ? On the drivers side does the seal go to the hood or sit on the box? Again the on the drivers side it has a drain tube, and the passengers has none ? I have had no seal on the passengers side so I expect that maybe part of the fume situation as well.

 

[DirtDonk]

The seals only keep engine fumes from entering the cabin air system.

The drain on the driver' side is only more obvious, but the passenger side drains naturally as well. But it's also prone to getting clogged up.

If you look under your fender where the plastic air intake plenum runs out of the cowl area and transitions to the cabin, there are three or four holes at the very bottom (and below the inlet level) where water will naturally fall out on to the road before it can enter the cabin.

If this area is filled with mud, leaves, critter crap and whatever else nature can throw at it, water will puddle and flow into the hose/cabin area.

Yearly maintenance is to either pull the hose and reach in there to scoop out extra stuff or push it out of the holes, or getting it from the outside.
I use a shop-vac to pull stuff straight out of the holes, but the first time after I bought it, it was literally packed with so much junk that I pulled the inside hose and vacuumed it out from the inside while poking at it through the holes with a screwdriver or something like that.

Just a part of Bronco-livin'!

Paul