After fighting this for a few months, trying painfully to figure out where water was leaking in and standing in the rear of our van in the trunk area – I finally found it and can get this thing repaired!
Shopping List:
In the rear of our Honda Odyssey, the ‘grocery getter’ area is a nice sized tub at the rear of the van where when the 3rd seat is flipped up, you have a very nice cargo area, and it also doubles as a place to house the 3rd seat when it is folded down giving you a flat cargo area instead. Over the past few months, this has been filling with water and emitting the most horrendous mold smell. We didn’t notice it until it started seeping up through the carpet, onto the folded down 3rd seat. One day we opened up the seat and found tons of mold, YIKES!
Since the rear carpet was going bad anyway due to years of stainage and multiple kids from multiple families spilling multiple drinks, we bought a new rear carpet from Honda (#83302-S0X-A00ZC), but before putting that in I had to figure out where the water was coming from.
After cutting the carpet out of the back cargo area, we found standing water UNDER the carpet. Somehow it managed to get in ONLY when the van was driving in the rain. Water did NOT enter when it was just sitting there. Apparantly, the tub is only tack welded in, and then sealed with some sort of rubberized bonding goo that hardens very nicely. Over time the areas of the tub where there were no welds have managed to bulge out a bit, breaking the bonding goo as shown in the picture below (after I had alreaded ground it away to make clean metal for my fixes)

Just believe me when I say, before I ground this down, the hole was just as big with a small amount of rust trickling down; revealing the problem pretty obviously.
Below are a few other areas I targeted for fixes as well, grinding metal down around them so that they can be covered with undercoating later.

Procedure:
- After ripping, cutting, tearing out the carpet, and cleaning up the water with a wet-dry vac, Use your putty knife to beat up & scrape most of the existing undercoating from the bottom of the tub.
- Using the wire brush or abrasive drill grinder, start grinding down all the areas and welds you see that have holes in them or are bent up pretty bad. Grind down to the metal
- Using your quiksteel putty, mash it up as per the instructions and jam it in the cracks as shown below:

* Note on picture: I also used another quickweld-type product in addition to the CarGo quiksteel
- Now wait for your quiksteel to set and harden, it requires 1 hour to be workable.
- Once your fixes are done, drape your plastic over the interior to catch overspray and use your spray undercoating to coat the entire tub area into a nice brand new cleaned up cargo space!

I shot some undercoating on the bottom of the van directly under the left & right drain plugs as well just to seal it up, your choice. Once the undercoating dries, WAIT. Go through a few rainstorms first as well as let the van sit when it’s raining bad outside JUST to make sure that you’ve gotten it all.
After a few storms, if you’re still dry then go ahead and have a drink… now you can replace your carpet (if you actually have a 2000 model I’d suggest you probably need a new carpet from Honda anyway, the rear carpet is only ~$280 or so).
Enjoy the rest of your day, you’re done!
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