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Fixing Water Leaks into the cab


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My truck leaks. First thing on my list is replacing the cracked windshield, and going with a late model rubber seal.

 

Next project will be door seals. I have opening wing windows, and really don't want to get rid of them. Are those seals available? All of the door seals are shot, so that will be a priority. I saw a thread that showed a supplier, but can't find it any more.

 

I found this thread, and will work my way through it: 

 

Any other suggestions on where.to look for leaks?

 

My 4x4 conversion will be on hold until I can get those done. I cleared space, stored axles, transmissions and transfer cases to get the Comanche out of the rain. I'm busy out of town until next month, and have some other projects in the hopper. Still, I would like.to start collecting those parts.

 

Thanks

Edited by BeatCJ
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The simple answer is "anything" but I think you're probably looking for something better than that. First of all, you should be commended for taking the issue seriously and recognizing the importance of fixing it promptly, because THIS IS WHY THE FLOORS ON THESE TRUCKS RUST.

 

To properly address the leaks, the interior will have to be mostly stripped. Baby powder will reveal leak paths. Sprinkle it along the floorboards to reveal which of the possible leak points are leaking on your truck. It's probably all of them.

 

It's my understanding that the vent window gaskets were available at one point, but no longer are. They leaked when new - a number of original owners have commented that their vent windows leaked from day one. The official "fix" from Jeep was to replace them with the fixed vent windows. The problem lies in the design of the window frame and seal. You can experiment with coins between the latch and the window frame - some people have luck with that, but for some, no amount of money is enough to stop them from leaking. I've seen it suggested to put silicone paste on the seals where water gets in. That will probably work, but will have to be re-applied every so often.

 

Just because the windshield is new does not mean it is good. A number of members have had issues with windshield leaks even after having it replaced. Once the adhesive cures, you'll want to test it to make sure it does not leak.

 

The firewall is where most of the water comes in from. There are five places that water leaks, going from driver side to passenger side:

 

Wire harness bulkhead connector - thank AMC for using a connector with absolutely no built in seal. The factory waterproofing method appears to have been packing the connector with dielectric grease. Unless you want to replace the entire bulkhead connector with something that's designed with a seal, that's probably the best you can do. You may want to consider putting some silicone paste or RTV on the shoulder where the "fusebox side" of the bulkhead connector sits against the firewall. Don't forget to put some sealant on the threads for the fusebox screws, as they go through the firewall too.

 

HVAC Seals (4 of them - heater/AC pipes, fresh air intake, evaporator drain, and blower motor) - These were all thick foam gaskets that have probably turned to dust by now. You'll have to make them yourself. These are such a big problem and such a pain in the @$$ to make for most people that I am seriously considering designing these gaskets and having them cut professionally. To do it right, a sheet of foam will cost roughly $75 and you'll have only a couple of chances to get the cut of the gasket right. To be brutally honest, these gaskets are above the average DIYer's pay grade. The gaskets for the 97+ HVAC box are still available, but they won't fit the older HVAC box.

 

If any of these gaskets except the fresh air intake leak, the water will run down the firewall below the carpet into the passenger footwell. The fresh air intake gasket will drip water on top of the carpet on the passenger side, making this the only common leak to be visible without removing the carpet. I should note that blocked evaporator drains as well as blocked cowl drains (under the windshield wiper mechanism) will also cause a leak in this location.

 

As for materials, I don't know what they were made from originally. They feel like foam rubber, but I'm not a foam guy. Thickness of the three on the firewall is roughly 1", but you may want to use a thicker material and allow it to compress. The fresh air intake gasket is the thickest of the bunch at around 1.5", but this one doesn't necessarily have to be a foam gasket - a properly formed piece of sheet metal would be OK for this.

 

Antenna Grommet - You'd think this wouldn't be as big of a deal as it is, but this is actually a MAJOR leak point in every MJ I've personally worked on. Water runs down the antenna cable straight into the cab. The grommets are different between power and fixed antennas. The power antenna version is more robust, and is still available new in the form of Crown Automotive's aftermarket power antenna.

 

The fixed antenna version can probably be made by carefully taking the antenna apart and replacing it with a generic grommet of the correct hole diameter. I don't have the measurements you'd need to hand right now.

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I drilled holes in my son's Cherokar. I want to do better than that. The truck as I got it was just too nice. I may be the wrong guy for this truck, it might be better to let someone that is looking for a preservation truck buy it and get something a little less nice. But, it's not perfect, so not doing that. But I'm not going to let it rot.

 

Thanks for the tips. I have already gotten rid of the carpet and pad. I think I will eventually go with some sort of coated floor, and rubber mats over that. Probably something with a good load of crumb rubber to limit sound. But first, trace the leaks I can find.

 

Again, thanks for the lists of things to look at. I haven't had a new windshield installed yet, any suggestions on how to make that as leak free as possible? I will take it to the local shop with the best reputation.

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38 minutes ago, BeatCJ said:

Again, thanks for the lists of things to look at. I haven't had a new windshield installed yet, any suggestions on how to make that as leak free as possible? I will take it to the local shop with the best reputation.

Probably not something you'd have to worry about with a decent shop. A lot of the discount chain windshield installers will slap a new windshield in without proper prep regardless of whether there's rust in the windshield frame area.

 

A good shop should at least tell you if you have rust in your windshield frame before just throwing one in with a huge glob of urethane and not saying anything.

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  • 1 month later...
16 minutes ago, rylee144 said:

Rather than start another leak thread I'll add here if that's ok. The leaks continue for me. Do I just call it quits and pull the carpet. I could then rhino line it and shop vac the water out when it appears. 

The adhesives and sealers are so much better today than when these trucks were built - the MJ gets garage queen treatment and stays out of the rain, so no issues with that yet, but the Cherokees are another story....been trying different sealers on the 88 cherokee - had a can of rescue 911 sealant (as seen on TV!!) laying around and used that in a few spots on the firewall, definitely cut down on the amount of water coming in and that was a half-assed effort.

 

Going to pull the carpet, use the baby powder trick and see if I can spray-seal the leaks up and how long it will last.

 

 

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I would bet that you could pull the trim around the windshield, mask everything up and the spray that rescue-911 (or something comparable) around the windshield and then put the trim back on - might try that if I find the windshields are the problem on the Cherokees

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On 10/11/2020 at 7:39 PM, BeatCJ said:

I drilled holes in my son's Cherokar. I want to do better than that. The truck as I got it was just too nice. I may be the wrong guy for this truck, it might be better to let someone that is looking for a preservation truck buy it and get something a little less nice. But, it's not perfect, so not doing that. But I'm not going to let it rot.

 

Thanks for the tips. I have already gotten rid of the carpet and pad. I think I will eventually go with some sort of coated floor, and rubber mats over that. Probably something with a good load of crumb rubber to limit sound. But first, trace the leaks I can find.

 

Again, thanks for the lists of things to look at. I haven't had a new windshield installed yet, any suggestions on how to make that as leak free as possible? I will take it to the local shop with the best reputation.

I pretty much always pull my own windshields on these trucks, do all of the prep, then either tape it in place and drive to the shop, buy a windshield and urethane, or have someone come out to the house. 

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Just now, rylee144 said:

Let me know how that works. 

Will do - have to confirm the windshield is even a problem first.

 

10 years ago was dragging a travel trailer through Colorado with the famdamily and had the gray water tank partially fall out and start dragging somewhere in the Rockies.

 

Didn't hear of see anything amiss (radio turned up to drown out the kids squabbling in the back seat) - anyway, drug that thing for 20 miles or so before I finally heard the noise and pulled over.  Jacked the tank back into place and secured with ratchet straps until we go to a campground in Colorado Springs.  Scraped a 3 foot long hole on the back corner that was 2" wide in places.  Went to local hardware store and bought some 3M 5200 marine sealant and some aluminum flashing - used a picnic table as a brake and bent that flashing to roughly accommodate the trailing edge of the tanks, loaded it up with 6 tubes of 5200 and pressed it in place with a couple bottle jacks.  Did some sightseeing for a couple days and let that cure. 

 

Had that trailer another 4 or 5 years and never had a problem with that tank - never leaked despite the massive hole.

 

 

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My windshield needs replaced, has a crack from roof to cowl. Interesting thought on doing the prep work myself. If there was rust in the seal area it would be nice to clean all that up.

 

I doubt it does, though, everything else is rust free.

 

I know I won't be going back to carpet. I think I will be going the Lizardskin route, with a Bedliner top coat.

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I can tell you BOTH my MJ's had gaps in seam sealer at overlaps of floorboard sheet metal. My '89 most noticeably when I POR-15 sealed it (as it made it's way through and dripped on garage floor). There were zero rust holes in the metal (California trucks)(. Freeway driving rain water was getting in through those gaps. Both MJ's oddly enough ONLY passenger side floorboard.

 

 

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Another place to check for seam sealer gaps is the extreme passenger side of the firewall. I've heard of water wicking through there and getting inside too.

 

This is why there's no easy answer to this problem, because the easy answer is EVERYTHING WILL LEAK.

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