Any advice on locating hard to find interior water leaks?

My 2008 Fit Sport is quickly earning the nickname "Moldy"...

These things are really well known for being leaky, but I seem to have stumbled upon a leak that isn't on the (long) list of common areas. Last summer, I fixed the very common leak that comes from behind the rear door panels and the car seemed to stay dry until right around Spring started this year. At that time, we were getting a lot of rain and I started getting standing water in the front passenger foot well.

I had been in a very minor bump that involved the car hitting a thin apartment car port post while letting the clutch out in reverse. It left the fender a bit misplaced by pulling it about an inch forward from where it would normally line up with then door on the side, and cover the windshield/seal on top. One thing to point out, is that I drove this car through the rest of last summer and this past fall and winter in this condition and saw no evidence of leaking until Spring. The new leak motivated me to replace the mangled fender, and when I had it off I used the hose to spray the front and passenger side of the car. I didn't see any water coming in from the door or door seal, but saw some water dripping from around the blower motor assembly behind the glove box. At that time, I was convinced that it was coming from the bottom passenger corner of the windshield seal that was exposed be the bent fender. I slathered some weather sealant on that corner and then secured the new fender. I daily drove the car for a couple of months and never really noticed any water. However, I let the car sit for a couple of weeks while we got some rain, and the next time I went to go in the car the passenger side carpet (front and back) was damp and moldy.

It seems the leak is coming in from somewhere in the vicinity of the windshield and/or firewall on the passenger side. Is there a way that maybe I haven't thought of that I can pinpoint the leak without removing pieces of the dash or even the whole thing? Or is there somewhere along the firewall that maybe I'm not thinking of that could let water in? I'm half tempted to put a lit smoke bomb in a metal pan on the passenger floor and see if the smoke escapes somewhere it shouldn't... Atleast the smoke will smell better than the mold/mildew...

Also, what would be the best way to get rid of all the mold/mildew, without removing the carpet/padding?

Thanks.

Does it have a sunroof? I would go out of my way to buy a vehicle without one. Unfortunately, all my non-Lotus 4 wheel vehicles have one.

For the RAV4 and the RN Truck, I put a desiccant container in them at all times. You can get one at Walmart with a semi-permeable film that won't spill. Damp Rid Closet something or other, found near the vacuum cleaners. That will pull the water out of the atmosphere and dry the vehicle out. When the magic power turns to liquid, I peel the film off on one corner, dump the liquid and refill it with bulk refill powder stuff from Lowe's, then duct tape it back together.

When I worked at a large dealership in PA back in the 70s, they had a crew that did nothing but water leaks. They would remove seats/carpeting/padding and place latter 2 in a drying room. Then they would remove kick pads/under dash covers/etc. and drive the car into a bay that had shower heads surrounding the car top to bottom. Powerful flashlight in hand, crawl under dash. Those 70s Mopars used to leak like a sieve. Customers would come in with inches of water over the carpets and go ballistic when they got the car back w/out carpets and were told to come back in a week.

In reply to Dr. Hess:

In addition to the sun roof, if there is one. My buddies Saturn Vue recently sprung a leak, and it wasn't the seal. The drain lines FROM the sun roof seal became disconnected, and were magically an inch too short to go back where they belong.

Maybe maybe get a windshield place to pull and replace the windshield if you think it's coming from that area. Just take i off, check the seals, and reinstall. I can't imagine it being super expensive to find out.

RAV4 1st gens are known for these issues. I spent a lot of time fixing mine. I eventually re-routed the left sun roof drain so that it actually drained outside the body instead of inside the body as designed. The inside the body drain would work as long as there were no leaks in the water path it was supposed to follow to get outside by itself. It's complicated.

Golly, has anybody mentioned sunroof drains yet?

You mention heater box. Is there a cowl drain that is blocked, allowing water to build up and run into the heater box? Is the condensate drain in the heater box blocked?

Generally, at my shop somebody goes inside with a flashlight, usually with the front seats out so you can see waaay under the dash without crippling yourself, and somebody else hoses it down from the outside.

Another possibility is to close all the windows, block the body outlet vent if possible, turn the heater fan on high, then hold a smoke machine or a lit cigarette near anyplace you think might be leaking.

Thanks for the replies everyone.

Thankfully, this car doesn't have a sunroof. Actually, IIRC, they weren't available on this generation Fit. If it did, that would've been the first place for me to check. I battled sunroof leaks on a Saturn Ion and now a Chevy Cobalt.

I did some poking on the web, and found that the glove box is easily removed and when absent, gives a real good view of the blower motor and some of the firewall on the passenger side. I'm going to pull it this weekend, replace the cabin air filter and look around for where it might be coming in.

We use to put a guy inside with a flashlight and another on the outside with a water hose.

I surprised ! A Honda leaks ? Two Fiestas and no leaks

Do you have a pool? You could submerge it and look for bubbles coming out. Have a look at the sunroof drains too.

I once saw an episode of Wheeler Dealers where Edd rented a smoke generator and put it inside the car. Then he just watched where the smoke came out.

jstein77 wrote: I once saw an episode of Wheeler Dealers where Edd rented a smoke generator and put it inside the car. Then he just watched where the smoke came out.

$20 Walmart Halloween fog machine is the poor mans version.