[water leak]

It didn't cause the leak. It's most likely the cowl drain, or a/c as mentioned.

 

It's just about spotless under the cowl. The drainage trench (?) that is not visible in the pic is also clean.

 

Did you pour water in cowl, to make sure it's draining properly?
Could be drain partially plugged (draining slowly.

 

I gently pushed a screwdriver into the hose, I stopped when it hit something.. one way valve? Can the grommet and hose be pulled out of the firewall?

 

Good idea.

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Don't put something in it.

Use a shop vac to clear anything that may be there.

 

The trench has drain holes at each end. When I pour water it exits behind the front tire, same on driver and pass side. The trench shows no signs of holding water. The problem is eleswhere.

 

It must be the A/C drain. Can I just pull the rubber tube and grommet out of the firewall?

 

gotta check mine if it’s clogged. Happened to my truck also. Only on passenger side when it rains heavily.

 

https://www.tacomaworld.com/threads/significant-leak-passenger-side.619833/

 

Op, the best way to clear the drain hose is to blow air back up the hose. Doesn't take much. If it's a plugged drain you'll get water running out afterwards. Hope this helps.

 

Thanks for the link. Good info.

 

Done. The drain sounded clear and nothing came out.


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You could pull the roof trim up and see if the holes are still covered with the factory paint. It's just a piece of 3M tape and plastic holding it down

 

Op, you've covered the usual things I have seen that could cause this. When you blew air back up the drain hose did you hear the sound of the air in the cab? That drain hose connects to the bottom of the plastic (tank) where the cabin filter is. I'm kinda out of options without hands on the truck. Wish I could have helped.

 

Take a garden hose and start running some experiments on different locations and see what you can find. At the very least it will isolate an area or if you have a sealed cabin and some other issue.

 

If the rain was a coincidence…

And it’s not clogged, nc can get pretty humid right? I was just there a month ago but I’m sure it’s hotter now. I’m sure you been running the a/c?

their was a guy in the “what you do to your 3rd gen” thread (sticky) that has a leak on passenger floor occasionally and a few others posted similar including me. I’ve only noticed it for 1 trip from fl-nc and that’s because it was dripping on the lady’s feet. My theory is it has to do with excessive condensation may or may not be linked to the recirc on (which also lead some of us to find out recirc automatically comes on when ac is on). That’s as far as I went because I havent noticed it in awhile

 

That high side must have hurt !!!!

 

Others have covered the usual. Check the cabin filter after rain/puddle - if it’s wet, it is coming in from fresh air intake in some way. You can also put a bright light under dash and see when/where you see light when checking the passenger firewall and windshield/dash area.
Good hunting!

 

This short rubber seal ONLY covers the area above the fresh air intake, so clearly it's purpose is to give added protection in that area. I removed it, cleaned it up and installed it with a bead of RTV. Also, the rubber lip that overlaps the full width of the windshield had crud packed under it. I'm pretty sure this will fix the leak problem.