Ok, so the wet weather is finally here. And of course it's just now that I remember that my cab leaks and I should have fixed that. The problem is, The leak is coming from under the dash directly under the passenger side heater vent. It's not the heater core leaking, just rainwater. Before I rip my dash apart, has anyone had the same issue and fixed it?

I have a friend with a 77 and it leaks there too, so I'm guessing it's a common problem.

Sam

 

Are your vent drain bowls cleaned out and free of debris?

If not, they can fill with leaves, pine needles, dirt, etc. and leak through the vents.

 

this stinks. I have the same problem with my 78 f150. Mine is the windshield leaking. I replaced and put new windshield gasket too. But there is rust under there so the damage is done. This one sounds like the drains clogged.

 

Mine has developed a small leak here as well. The new windshield was leaking between the gasket and the glass but I'm pretty sure Ive got that fixed. Montana, you mean the cowl bowls, right? I cleaned those extensively about a year ago, I'll check them. Where would the water enter the cab if this is the case?

 

Yes, that's the correct term, mine were packed so full of pine needles that when it rained more water would leak through the vent than would filter down through the drain hole.

 

I think I know where they are, should I just go in there with a hose and spray them out?

Sam

 

If they're not all gunked up with trash that method will suffice, but if they're packed full of debris you may need to work a wire coat hanger up through the drain hole.

The drain hole isn't very large, less than an inch in diameter iirc, it's easily blocked if not cleaned out regularly.

 

That makes sense. Where exactly is that hole?

Sam

 

They're at the very bottom of the cowl bowl, if they're not blocked you'll see water flow from them when you take a hose to it.

 

Front view of the cab. See the rubber hole plug on the rounded piece on the right. It is at the bottom of that cavity.

I like going in through vents inside cab and from the hole on the bottom to get it all. Blowing air from the cowl vents helps also.

 

Grinner, thanks for the pic.

They must be gunked up, I was one the freeway and pine needles and leaves started flying out of the vents!

Sam

 

It was definitely full of gunk, I cleaned it out, but it still leaks...

That vent assembly just screws into there doesn't it? I think my next step it to pull all that out.

Sam

 

Removing the vent will enable you to get ALL of the trash out of there. Couple of screws and it comes right out.

 

my firewall seem is rusty, where the cab floor meets the metal approx 6-ish inches under the windshield, you can see the seam from the engine bay, it is that lip that goes horizontally behind the engine heads, i may or may not get a new cab for the truck, we will see

 

Thanks guys, and especially for the photo, Grinner. Had the same problem with my 1986 F250 and always thought there must be a gasket or seal under the cowl that needed to be replaced. Will now go after cleaning those bowls....thanks again