How to find a leak in my car?
April 8, 2010 3:46 PM   Subscribe

Water is leaking into the car. Mechanic says ask the glass people, the glass people can't find the leak.

After the torrential rains of the last couple months, we noticed a significant amount of standing water in all of the footwells of the car. The wet doesn't seem to reach much above the level of the actual puddle. At its highest, there was about an inch of water.

We initially thought it was something mechanical leaking into the car; the mechanic says it's not. The car just spent a day with the glass people, who couldn't find a leak and want us to pay them $50-$100 to take out all the seats and carpets and look at the body. This is unappealing -- we have no guarantee they'd find anything, and given that they didn't reassemble what they took apart the first time, I have very little faith that they'd restore the seats and carpet properly.

Anyone know of a good way to find the leak? Failing that, a really competent and trustworthy business in the Boston area that will find (and/or fix) it for us?
posted by contrarian to Travel & Transportation (15 answers total)
would help to know what kind of car. I had a Olds Intrigue that would leak through the heater blower motor into the passenger footwell when it rained really hard.
posted by cosmicbandito at 3:55 PM on April 8, 2010

Best answer: Dick's Auto Body in Somerville is pretty great and helped me with a similar leak (in my case, the trunk seal failed after a rear-ending--have you checked in the trunk, in the compartment under the bottom, where the spare tire is?)
posted by phoenixy at 3:56 PM on April 8, 2010

Could be coming from a cowl vent. We need to know what kind of car.
posted by Big_B at 3:57 PM on April 8, 2010

Response by poster: It's a 2003 Mazda Protege. There seems to be a bit more water on the passenger side, but there is water on both sides, both front and back.

I will check under the spare tire.
posted by contrarian at 4:00 PM on April 8, 2010

This happened to me once and it turned out to be a clogged drain on the bottom of a door. There was a glop of mud stuck on the bottom. I suspected as much because I could hear water sloshing inside the door when I swung it.

Anyway at one point I talked to an auto-glass place and they said they have all kinds of fancy equipment to test for leaks but it costs a few hundred bucks (?!). There are all kinds of seals that could fail and they can test each one individually. Maybe you can examine them first yourself.
posted by PercussivePaul at 4:05 PM on April 8, 2010

Response by poster: There is a ton of water next to the spare, and in the spaces for the jack and etc.. A trunk seal you say?
posted by contrarian at 4:07 PM on April 8, 2010

This is pretty obvious, but, like, are you sure you didn't leave any windows open? Sunroof?

(If it was my car, that would be the problem.)
posted by Sys Rq at 4:13 PM on April 8, 2010

The best and most reliable way to find the point of water infiltration on any car is to hose the car down and see where the water comes in.
This process requires two individuals. One to hose the car down and the other to shut themselves inside the vehicle.
Person number two, inside the car, will contort themselves and peer under the dashboard to see if water is infiltrating via the cowl or windshield. They'll equip themselves with a flashlight and check the headliner at every point, crawl into the back seat, checking the door pillars and door seals, and then crawl into the hatchback area or fold the seats down and crawl into the trunk area.
The most common sources of water in a car are:
Sunroof drains
Door seals
Clogged HVAC drains.

Good luck
posted by Jon-o at 5:43 PM on April 8, 2010

Do you have a sunroof? When this happened in my car it was because a drain tube that led from the sunroof opening down to the bottom of the car. The sunroof doesn't actually seal, instead there is a gutter around it that collects the water and it gets sent down the tube to drain through the window pillars. Leaves and such can get into the tubes, and it somehow leaks out into the floorwell.
posted by procrastination at 5:48 PM on April 8, 2010

I have a 97 Mazda 626 with a leaky trunk. The water comes in through bad trunk seals, runs underneath the fabric flooring, and into the spare tire well. You can't tell it's wet just looking, but if you pull up the tire cover you can find a small lake in the tire well. There should be a rubber stopper plugging a drain hole under the spare tire. Pull it out from under the car and that will at least drain the truck.
posted by COD at 5:55 PM on April 8, 2010

Best answer: The trunk lid and seal is where water got in with my last two cars.

The standing water in the spare tire area suggests to me that this is your source.

I am not familiar with your model of car, so the following may not be exactly right, but here's what I would look for.

Remove the trunk seal (the gasket between the trunk lid and the car body) and see if it's wet along the inside groove. Look for unexpected bends in the metal flange that the seal goes on. Sometimes, closing a trunk lid, an object gets stuck here and bends the flange, preventing a tight seal.

If the flange is bent, straighten it and put the gasket back on and see if this stops the leaks. If it's not bent, but there's water in the gasket, replace it (good time to clean any mold / gunk off the flange, too).
posted by zippy at 6:11 PM on April 8, 2010

Does it get wet if the car is standing still, or only when moving?

My 1998 Jetta gets water in the trunk only while driving in the rain. There's a spot where the rear wheel kicks water up onto the bottom of the trunk and it gets in there.
posted by chazlarson at 7:25 PM on April 8, 2010

That's funny, my car is an 03 Mazda Protege too. Could be this issue is a tendency with the model?
posted by phoenixy at 9:52 PM on April 8, 2010

Response by poster: My completely unscientific googling indicates that yes, a little. The car hasn't been rear-ended, but we have been carrying around a lot of trunk-seal-abusing stuff (piles of wood, etc..). Having not yet verified that this is the problem, I am guessing we messed something up doing that.
posted by contrarian at 5:10 AM on April 9, 2010

Response by poster: Follow-up: The leak was in fact in the trunk and according to Dick's was probably caused by someone clipping the bumper. They fixed it.
posted by contrarian at 9:53 AM on April 27, 2010

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