Up under the drivers side dash - up and a bit to the right of the fuse box - there are some body seams. I'm having a hell of a time trying to seal up some leaks I have. Everytime it rains I get leaks in this area.

The main problem is I cannot find how to access this area from outside the truck to seal it up, and inside there are so many seams it is almost impossilbe to seal (that and incredibly difficult to work on). Part of this area is under the hood near the throttle cable, but after some good fiberglass work there, and under the dash, I'm still getting water in the cab.

I have no idea if that makes sense, but I'm hoping that those of you familiar with the truck may be able to gather what I am talking about and offer some suggestions.

there is a welded seam where the door support, cowl support, and firewall all come together. this area develops pin-hole rust perforation and leaks into the cabin. the easiest way to fix it is to pull the cowl panel off, stick a floor jack under the opposite side of the truck, jack it up as high as you can, and pour about 1/2 cup of brush-on bedliner down the cowl vent. it will fillthe pin holes, and the excess will run out the side behind the fender. if you have big holes in the cowl, you may need to do this procedure two or three times to get sealed.

Thanks for the response Sundowner.

I tried pouring a bunch of fiberglass resin down the corner with the cowl off, but I didn't have it jacked up I guess. Is this the area off to the far left almost under the hood where you can see it open down below? Let me know if pics would be better to explain.

do 91's have this problem also or is it just 1st gens i have a leak somewhere on my passenger side

BEFORE you pour anything down there make sure you got all the rust out. i had to take off my fender, peel the seem apart, get all the old sealer out, sand the rust down completely, coated it w/ some por 15, and then sealed it up w/ some seam sealer. make sure you do it right or else youll be going back in there again soon.

but there is a possibility that your windshield is leaking.....

How do you get to this seam if you pull the fender off?

Another thing to look at is rust around the windshield. I had some holes and water leaked in and then ran down behind the interior panels pooling of the floor.

I have been fighting this same battle!! The first time I accessed the inside of the cowl I took both fenders off and cut out the subframe section that covers the cowl channel (metal surrounding the approx 2" drain hole) cleaned the area up and welded in patch panels of sheet metal then tared the crap out of it.
Once finished inside the cowl channel I welded the cut out pieces back in place.

I still have leaking problems though!!! I believe that I didin't do a good enough job sealing the holes (I used a cheap handy core buzz box for the welding with not much experience).

Interesting idea of using bedliner to seal up the channel, I have heard of pouring liberal amounts of cleaner as a prep(paint thinner, acetone etc..) and then using marine grade fiberglass epoxy resin poured into the access panels on top of the cowl in coats.

My rust is really bad in there though, and has gone right through the seam where the firewall, wheel well , and cowl channel meet. Its the area under the hood that is right below the windsheild wiper motor assembly on the passenger side and under the clutch/brake booster on the drivers side. I have also welded in patch panels there!

A toyota tech that I know has an 89 4runner (gen 1) and he accessed the cowl channel by removing the wiper motor assembly, the hood, and hinges. This wont work on my 89 p/u because I have a different hinge and wiper configuration with the newer body style!

I have considered plugging the cowl channel access vents on top to prevent water from entering but I am currently debating it's implications as to where the water will go and I will be sucking air for the cabin from the side access ports under side fender instead of fresh air on top.

Also its good to mention that since I have leaking water pooling in the footwell areas I have relocated my engine computer into the glove box to keep it dry (see 4crawler's site for how to in the cheap tricks section). I just wonder how much of my wiring is corroding!! My circuit opening relay bit the dust last winter from rust as well.

About the leaking windsheild thing I removed the interior plastic A pillar covers on the sides of the windsheild and all looks good, I am still planning to remove the dash for a better look but have not had the time because this is my DD!
Oh well sorry about the Long post but it is nice to hear other people have this problem as well, I am just trying to share my experiences/frustration so far.

Please if anybody has and other useful info please fill us in... so we can fill our holes with something good ( and solve this problem!!!).

well i just ripped my fender and cowl off and i didnt see any rust (yay) but if i poor water down there it goes right in i wanna poor some fiberglass or bed liner down there but im worried its gonna clog a water something that should be clogged. if off to the zone to buy some stuff. i let you know how it works i just wanna let things dry in there and i also have to wait till the rain to pass got a little wet takin the fender off <img src="/forums/images/graemlins/kewl.gif" alt="" />

Sounds good!
Let us know how she goes eh! Just remember to clean the area really good before painting <img src="/forums/images/graemlins/oink.gif" alt="" />