My '98 accumulates water in the passenger side's recessed floor area.
It accumulates when the vehicle is just sitting, not being driven, and it rains.
Gotta get it stopped before the floor rusts out.
I can see no obvious source for the water to be coming from.

MY assumption is that it is probably coming from somewhere around the windshield.
But then, this vehicle originally came out of Minnesota.
Apparently, they were still using rock salt on winter roads when this truck was still new.
It has a definite rust problem in many locations.
Although, there are no signs of actual cancer except one spot on the front bumper.
So, I'll allow that rust might be the reason for the leak.

I'm thinking of applying a caulk around the perimeter of the windshield to see if that will stop the leak.

Any suggestions as to how to check for, find and fix this leak?

 

I did auto glass replacement for 12 years. The way we would find leaks around glass is to spray a foaming glass cleaner around the edges of the glass on the outside, then shoot compressed air from the inside and watch the foam for movement. Look for a glass cleaner in HomeDepot called Sprayway. It's good stuff.

Top edge and sides of windshield is usually fixable, bottom edges aren't. (you cant get urethane up to the existing bead)

Be careful with the urethane though, it will transfer to anything it touches, and it is almost impossible to get out of fabric. If your leak is on top of the windshield, I would remove or at least take the headliner loose to get it away from the fresh urethane while you apply it. (You have to seal the top bead from the inside, the trim molding on the outside would need to be removed in order to add urethane to the existing bead. You risk cracking the glass when you remove it. Side moldings are screwed in with Torx, so you can access the sides from the outside.)

I would advise against using regular caulking to seal it, You never get a good enough bond with that stuff, and it makes the next guy's life miserable when he has to clean it off. It can also cause adhesion issues if the next guy doesn't clean it off totally.

If you trace the leak to the windshield, it's almost better to just have it replaced. A local shop here just quoted me $100 cash. To save the cost of supplies, and hassle of doing it yourself (and possibly getting urethane everywhere) it's worth it.

 

I finally found cans of Sprayway at the local Ace Hdwre.
I'm finding no leaks around the passenger side of the windshield.

I'm not so worried about the floor rusting out anymore.
There is a urethane[?] pad adhered to the floor under the carpeting.
It doesn't look as if water can reach the metal of the floor.
Plus, the paint in that area is in good condition, no metal showing.


The 6 screws that hold the side windshield molding through its length are very rusted.
It looks as if they could possibly leak over the door and down the A-pillar, maybe allowing water to reach the passenger foot area.
Nothing to indicate that, just suspicion.

I think I might pull the carpeting out and see if I can find where it is coming from the next time it rains hard.

Still open to thoughts on what might be going on here.

 

Both my 97 and 99 do the same thing. My 97 isn't bad but the 99 is like a pool.

 

You should take a look at your AC drain tube.. They are notorious for leaking back into the passenger floorboard area:

https://www.youtube.com/watch?v=XXHLnYxvJTg

I would treat the rust on those screw holes and prime, then seal with silicone or urethane, just as a precaution

 

The AC condenser has a leak in it.
So, I don't use the AC.
I think that would eliminate the drain tube as a water source.

I will clean and seal the molding screws. Then, if that doesn't stop it, I'll remove the seats and carpeting to see if I can locate the direction it's coming from.

 

The only other things I can think of to check would be your rubber door seals, and possibly the side mirror assembly seal.

Do you have a extra cab or the four door? Do you get any water in the rear passenger floor area?

 

I had a problem with the REAR window seal leaking allowing the water to run in and toward the front passenger floor area. The rubber round the perimeter of the glass itself, not the sliding piece. When the window was replaced the original guy slit the rubber and nobody found it until the THIRD replacement was installed. I also had a problem with the drain tube from the A/C on the firewall and though you said you don't use yours I wonder if you use the defroster? That would trigger the A/C system although is the condenser is leaking I'd guess you wouldn't generate condensate either.

I believe I've also seen comments about the radio antenna cable being a possible problem as well. There's a grommet or two where it passes through various places that might allow water entry.

Then again you could do what I did years ago on a vehicle I couldn't stop leaking. Remove the floor plugs so it could run out again!

 

I did cleanup the screw holes and added a rust hardener to them. Then, I added silicone caulk to the holes and screws. There was a small tear in the upper corner of the inner weather stripping of the door frame. I sealed that with the silicone caulk also.

I did leave a windows open one night when it rained and the driver side got wet also.
It has been unusually dry this winter, [You northern tier types can go ahead and laugh at my use of the tern winter for this time of year here in Hawaii.] but, it has rained hard a few times and no water has gotten into the passenger side. In fact, it is actually dry right now. I think the problem is fixed. Now all I need to do is get the driver side dried out again.
Thanks for your help guys.