Have you battled with a mysterious oozing liquid in your car?
Zach from Oregon has got a dirty secret. His Honda Civic is leaving his backseat passengers with something memorable.... a wet brown stain on their pants! Zach swears there's no odor and no visible leak or ancient cup of spilled coffee back there. What gives? (Hear the call, right here.)
Zach needs to put his car on a hoist and check the rear wheel liners. On most cars, they are directly below rear seat and when they rust thru the rear seat gets water thrown up by the tires. Very common problem with vintage cars like my 1995 Olds regency 98. I anually have new coating sprayed on the wheel wells to slow down the process.
I had this on a 97 prelude. Problem turned out to be a cracked taillight that allowed rain to leak into the trunk, it setled in the spare tire wheelwell. When you hit the brakes the water is thrown forward, under the carpet, into the pocket formed under the back seat. You can’t feel the water with your hand by rubbing the seatbecause the foam seat bottom rides just above the metal floor, but when you sit on the seat, the foam pushes into the water and acts like a sponge. Hand force is not enough to do it. Wit full body weight, you get a wet but. It’s brown due to the rust in the water. This can come from a leaky rear window seal or trunk seal, or as in my case a taillight. Follow the dried water stain under the carpet in the trunk, or run a hose over the car while looking inside the trunk through the folding back seat.
good luck
fairmank5 nailed it. I have '96 Civic. And I also live in Portland. The thing with Portland is that it rains most time of the year. If you have a cracked taillight, or bad seals on the taillight, the water from that taillight leaks into trunk every time you open it. From there it makes it right under the rear seat and under the carpeting in the car. I
had to battle mold problem in my car because of that. So the
answer is simple: if you have wet pants, check the seals on your taillights 
Thats so funny I also have a 2004 Honda Civic and I also battle with the same oozing liquid!! It all started one day after one of my cousins stood up with a brown spot right on her bottom. Their was nothing visible untill I pored a little water and I wyped that I saw that brown stuff. Its every were on my carpet and on my seats. I thought I was going CRAZY I tell people and all they say is you must of spilled something!!! What can we do about it???