Copperhead

I had the same issue mainly on the passenger side and partially on the drivers side. Had to patch a good section of the passenger floor. On the driver side it appears the floor plug(?) rotted and allowed water to enter from below. I imagine it wasn't a lot of water and was able to dry out from time to time, hence not a whole lot of damage.

The passenger side was another story. It took a lot of sleuthing with the carpet removed to find the cause of the leak in my case. The firewall has a lip on top. The rain flows under the hood at the fire wall and SHOULD find a way harmlessly thru or along the sides of the engine compartment. In my case, and I'm sure many others, some of the water gets diverted down along the firewall and between the blower seal(which appears to be just a foam seal) and the firewall, out under the dash and settles onto the passenger floor.. And it can be a LOT of water that gets by...and by my observation, it never had a chance to totally dry out, even when the carpet seemed totally dry.

I thought about how I could waterproof the blower motor seal, but you can't do it from the inside. If you do the water will only accumulate inside the blower housing and leak anyway. Sealing the outside seemed like the solution, but I still couldn't see why this should be necessary. With a little experimenting I was able to create a wimpy "overhang" off the firewall out that sticky aluminum duct tape. Now when the water flows to the spot where the water wants to run down the firewall and into the blower seal it now flows another few inches outward and falls harmlessly to the ground.

Hard to believe this simple 3 minute flimsy mod solved a problem that caused over half of my passenger floor to rust out. .

1/1200 Cherokee

I’ve dealt with ripping up carpets to find standing water too. Thankfully I’m in Pacific Northwest where there’s no salt to rust anything. My XJs leak ended up coming from engine compartment under antenna like the image above. The leak went down the passenger side all the way to the rear seats. I RTV’d the heck out of that area and never had a leak again.

Spencer_P

How do you go about resealing the antenna? Can a new seal be had or do you just remove it and put some RTV around it?

country2

If I remember correctly I just put some urethane sealer around mine after I pulled it out some. You can get the complete assembly with the seal on it don't think you can get just the seal.

Rambler65

I may have to take a look at that. In the drenching rains we got over the weekend I wound up with water coming in behind the dash despite having a cover over the windshield and cowl. (That didn't happen in the previous rain.) Tracking down these leaks is really frustrating...

Copperhead

Don't know if the OP said he already done so, but IMO the only way you are going to verify where the leak is coming from is to remove or at least pull back the passenger side of the carpet. Take a hose and run some water down along bottom of the windshield with the hood up. Check along the firewall to see where the water is flowing and/or being diverted. Keep checking inside the vehicle for where the water is entering. Try to eliminate specific areas where the water infiltration could be taking place.

RockyMtn96XJ

I would start with a slow water flow so it stays in one area rather than a crap ton of water going everywhere. It will probably be easier to see where its coming from. If that's not working too well, flow some more water. Windshield, cowl vent holes, under the hood on the firewall, blower motor seal.... Everywhere within about 2 feet of that corner of the Jeep.
I'm tempted to take the carpet out of the front and somehow attach it to the floor so it doesnt curl up or get messed up, maybe some good velcro to attach it to the floor, or some silicone sealed rivets.... then truck bed coat the front floor boards. I have nice rubber floor mats that cover the whole floor, so its not like I can see the carpet anyway. Then I can keep the cheaper floor mats and not upgrade to weathertech since it wont matter if I get dirt, water, snow, etc in there, I can just wipe it out. This will just be some preventive measures in case the day comes I get a leak as well.... knock on wood.

now that I think about it though, maybe starting off with fast water flow can get you in the general area quicker, then slow it down to see a precise area of leakage.

GzrGldr

I would suspect the cowl. There is a raised vent opening on the passenger side. You can't get to it by removing the cowl assembly as it is under sheet metal, but the seal around the base of it goes bad. If you have a scope camera, you can get in there and see if that is the problem from the center portion of the cowl. Water gets into the cowl and if there is enough water, it overflows that vent opening. Here is a really good video showing where this is and what it all looks like. I wouldn't recommend repairing the way he did personally, but it gives you a good idea. This is a really common source of the water leak on the passenger side. And, like others said, so is the blower motor, however, based on what you described with a sustained rain over a long period of time, I would highly suspect the leak is coming from the cowl. For it to come in from the blower motor, it would have to get pretty wet in the engine compartment.

Copperhead

I thought it was that raised vent too..but it was pretty easy to verify it wasn't my issue. As to the amount of water in the engine compartment, there was nothing evident after the fact, besides a small line if wetness on the firewall. I even dismissed the blower housing at first because of how much water was entering on the passenger side. Obviously there are a few different possible causes. Hope the lets us know what his ends up being.

country2

If I'm remembering correctly my leak from it was mainly on the kick panel side not front of dash area. I will look and see if I have any picks of that area when I had everything ripped out maybe it will jar my memory.