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Interior Leaking Bad - What could it be??

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I am restoring an ‘87 Comanche and the interior is leaking bad.


I had all new interior fabric pieces installed so I am very concerned. 


The floorboards did have holes at one time, but I had them repaired and sealed.  In addition, I had a new windshield installed

and I’m almost certain there is no leakage from there.


The water seems to be collecting where your feet rest (both passenger and driver sides). 


This might be a stupid question, but there are some holes in the rocker panels. Could this be the problem?


The water seems to travel from the outside edge of the truck from the back of the cab to the front, then finally resting at the lowest point where your feet rest.


Thanks for any advice.






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My sliding back window was leaking. When I took it out there were inches of sealant that were not adhered to the window. They also say the vents on the sides can leak. This sounds weird but what I did for insurance against that was put an eyebrow shaped bead of silicon above each hole and let it dry before putting the covers back on.

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The first places I would start looking are the wire harness junction behind the fuse box on the driver side and the antenna grommet under the passenger side kick panel trim. Also the HVAC connections on the passenger side. The fresh air intake on the passenger side can drip directly on to the carpet. The rest would tend to leak under the carpet. These are all common leak points. If the water comes in at the rear, the rear window is the main concern, but it's very possible there is more than one path and I would not immediately dismiss the front firewall as one of the possible leaks.

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Take a hard look at the rear window glass where it is set in the metal frame. Mine looked like the rubber between the glass and the frame was deteriorated. I ran some silicone caulk around the glass and frame. Wouldn't be surprised if the weatherstripping on your slider was worn out too. Agree on the radio antenna grommet, although that should only affect the passenger side (mine had fallen out).


There are several posts on the site in reference to water leaks. Review those if you haven't already. In them you will see a recommendation to use baby powder to help track down leaks. 

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  • 1 month later...

Thanks for all your suggestions.  I have taken almost all the interior pieces out until I find and fix the leaks.


Last week we had a severe storm with heavy rain. Inside the cab, where the passengers feet go, there was a pool of water. To give you an idea, I placed my hand flat on the floor and it was submerged to my knuckles.


I felt around the windows and doors to see if I felt moisture leading to a leak, but couldn’t find anything. 


Interestingly, the drivers side was not wet at all. In my previous experience with heavy rain (driving through it) the drivers side was very wet as well.


I am flabbergasted as to how that much water is getting into the cab.  I am going to continue searching for the leaks, but I’m starting to lose my patience. This is the only thing keeping me from driving the truck.  



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The leak is likely in the cowl.  There is an opening on the passenger side to allow fresh air in.  Sometimes the sealant around that vent can fail which allows seepage during heave rains (as the cowl will fill with water and drain out the sides).


I have a leaking problem in my '88--the passenger side floor gets super wet when it rains.  I haven't tackled a fix yet, as I'm not 100% sure on what to do without taking out the dash and HVAC box, but I'm about 99% sure this is the problem.


This thread describes it perfectly:



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Check the blower motor opening from the engine bay. There is a piece of foam that mounts from the inside at the blower opening and also where your condenser lines come in to the cab. 99% chance it's original and 30yr old foam dries out leaving gaps and water finds its way in there for sure. Believe it or not, you can still get these foam pieces but it involves, IIRC, pulling the dash to replace them. 


I had the never ending leak on the pass side also and I believe the 2 main culprits were the blower motor opening and the radio antenna opening behind the passenger kick panel. For both of these areas, I bought rubber butyl and formed it around the openings. I did the antenna opening first and the amount of water coming in reduced a fair amount but in heavy rains I was still getting water and I could see it trickling down from under the dash so that's when I did around the blower motor and other areas in the engine bay. Knock on wood, cab has been dry ever since. I'll post pics later. 

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2 hours ago, Minuit said:

I'd be very interested in what product you used.

I researched seam sealer, butyl tape, butyl rubber, there are lots of name variations but as I was searching for the multitude of possible leak locations on XJ/MJs I came across somebody that used this product to seal the leak they had around the vent that comes up through the cowl. Anyhoo, lots of brands out there but the Advance Auto website said they had the 3M round seam sealer in stock but when I got there it was a different brand. Got it anyway because it was what I was looking for. I've still got the box at home so I'll post that later. There is flat "tape" and round and they come in different thicknesses and widths. I used round but the flat tape probably would have worked well in the applications I did because I definitely worked the round bead a lot. 


Stuff is verrry tacky so I used latex gloves and then read a tip about spraying the fingertips of the gloves with WD40 to not only keep it from sticking to the latex but it made it much easier to form or push in to place. I also found that it was easier to do it in short pieces especially in tight places. I had tried some rubberized spray like FlexSeal before I came across this, and again, if you're trying to hit a certain area in a tight space it just ends up a mess. Cost runs @$0.75-$1.00/ft, well worth it. Since my interior was apart I also applied some around my back window where some original seal had deteriorated. 


You can see in the main pic the amount of material I put around the blower motor and "folded" under the metal edge to the factory foam. Because another location of water intrusion identified is on the cowl seam, I loaded up there also. In the second pic I also put a bunch in the corner where the fender panel meets the inner fender as water can go down there and get in through your radio antenna cable opening. Last pic show where I applied it around the foam where a/c lines enter the cab. If you look hard down past the white, green and yellow vacuum lines in the first pic, you can somewhat see where I also put it around the a/c condensation drain. I tried to hit as many areas of possible water entry as possible. I did this about 6 mos ago and we have had some major rain in our area the past year, and fortunately it remains dry.  


Some good info on butyl rubber........







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Here is the brand the Advance Auto, or it may have been Auto Zone, had in stock when I bought it, Metro Supersoft. You can get this brand online also. 




Picture is the grommet in the radio antenna hole that exits behind the passenger fender. I sealed the based with the rubber butyl then sprayed it with a flex seal knockoff for a little extra protection. 



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Thanks for all your suggestions. I really appreciate it.  


It turns out the weatherstripping was not making full contact with the truck and water was just pouring in.  

We put a 1/2" diameter rope between the weather stripping to push it outward to make contact with the door.


I've had no issues since.  

My only concern is how the cotton rope will react with the metal of the truck.  If it retains water, would I have to worry about rust?  

I thought about wrapping the rope in electric tape.








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On 5/9/2019 at 12:40 PM, Pete M said:

I would go with the 97+ XJ doors seals.  they are a bit thicker and seal much better.  :L:  I would never leave cotton rope where you put it

That might be worth trying. Thanks for the tip.

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