Need help finding a leak

I was working on my 1990 XJ and noticed a small amount of rust on both sides (driver & Passenger) front floorboards. I went through the labor-intensive process of removing all the carpet and insulation to treat the rust and then try and identify the source of the water. I took it to my body shop and they had a hard time finding it.

Here is what we know:

Driving through deeper water is not the source.

When the vehicle sits out in the rain is when water will start to puddle on the floor.

It runs down the firewall behind the rubber and foam firewall insulation mat.

We are not talking huge quantities of water; maybe after a day of rain it may be a total of a 1/8 a cup.

For some reason there is more on the drives side then the passengers.

The water appears to travel down and puddles nearer to the doors on the floorboards, as opposed to nearer the transmission hump.

Wondering if anyone has had some similar experience and help me so I don’t have to reinvent the wheel so to speak in fixing this.

Thanks for your help,

Fred
Explorer 1

I have the same problem... I wonder if you take a waterhose and spray it in certain areas if you can find the leak. I know my little triangle shaped mirror leaks on either side and I suspect my door seals leak. Did you pull the carpet right above the muffler? That's where most of my rust came from. I then rhinolined everything that wasn't rusty and cut and welded new sheet metal in the areas that needed it.

1) Your weatherstripping is 17-18 years old - may be time to replace it.

2) The vent cowl behind the hood should have a drain - maybe it's blocked? Sorry I can't give you more detail than that at the moment, but it's an idea.

Since you mention it happening when it rains, the weatherstripping and vent cowl were my first thoughts. I'd also take a flashlight and a mirror-on-a-stick and check the grommets and seals for the wiring coming through the firewall, just in case. If they're cracked, some RTV Black will usually patch them back up.

Thanks for the suggestions.

I pulled the entire carpet out of the whole vehicle. From the rear of the driver and passenger seat the carpet had already been removed. I rarely have more than one passenger so my back seat is out and I designed a level extension of the rear cargo area so I could have some storage area where normally rear passengers would put their feet. This is where I have my 2nd battery and isolator.

The body shop said they checked the cowling and firewall and did not find any leaks, so I with you in thinking that it might be windshield related. At this point I think I'm going to tape up the cowl with some plastic so no water can get in there and then set a sprinkler on the roof and see if water puddles inside. If so, I'm going to go ahead and bite the bullet and just replace the windshield rubber without identifying exactly where it is coming in.

I more concerned about stopping the leak then knowing exactly where it comes in. When we pull the windshield I will also check for any rust around where it seals.

Your right, as it is, I’m surprised that it hasn’t started already. Probably lasted so long due to having may of it years stored inside.

I’ll let you know,

Thanks again,
Fred
Explorer 1

I have the same problem, but if i leave mine in the rain over night, there is about 3 inches of water puddled up. I removed the carpet and found the water to running down the roof pillar right infront of the door. I tried sealing up the bolt holes in the roof rack but that did not stop it. My last resort is to also change the windshield rubber and hope that is the problem.

We have been chasing a water leak and finally had the windshield pulled out of my son's Jeep yesterday. There was only about 10-12 inches total of the urathane still holding the glass in. You could actually push the glass out of the frame a quarter inch or so in the middle by the mirror, the seal was that far gone. Mainly because the frame had rusted that bad. We got the frame all taken care of and the glass back in tonight. It was well worth the $75 spent from a safety stand point, even if there is still a leak.

On early model xj's they're notorious for leaking around the windshield gasket. Easiest way to do it is take it to a shop that replaces windshields and have them pull the old one clean the area up and then reinstall it. Almost all xj's that have experienced this leak always seem to be on the driver's side.