water leaks

Sounds like you might have a heater core leaking..

Heater core

Could also be the windsheild thats not well sealed

Does it smell like coolant? Heater-core. No smell? Windshield leak, sunroof drains, or AC condensate drain.

If it does not smell like coolant and there has been no body damage that could affect door or window seals, then it's probably one of three things. 1. It could be a leak from the sunroof but if it is then the liner should be wet and a seal is damaged or the sunroof drain is plugged. Look online for a video on how to fix. 2. It could be an air conditioning drain hose plugged or disconnected. Pull up the front passenger carpet and you should see a drain tube exiting through the floorboard. 3. Most likely if you have a lot of water on the passenger side floor after a rain or a wash, it's a plugged drain hole at the bottom of the windshield cowling - that part at the bottom of the windshield with slots in it. Open the hood, use your fingers to release the plastic fasteners, remove the rubber and the metal cowling, then look down in the opening near the passenger side for debris plugging the drain hole. Clean it out, reassemble, and you should be good to go.

Could just be a dirty gasket not sealing well. Clean it off with mild detergent & water. Age with these guys about clogged drain hose, too.

Meaning the square-ish sunroof gasket.

My 2009 Matrix had wet floor in passenger side. Checked drain hole in sun roof, completely plugged. Cleared drain, should be the floor leak fixed.

Sorry! Floor on passenger side soaking wet after it rained all night,,so I guess the sunroof drain not the problem after all. I will try the windshield cowling next as per Stan's solution no. 3 above.

Make sure the rubber gasket seal around the glass is clean. Simple accumulated dust over time made mine start to leak. I wasted $40 on a new gasket when it was a simple cleaning and maintenance issue.

What did this end up being because I'm having the same problem?

Clean your gasket with mild soap, water, and paper towels, SHOULD take care of your problem. Make sure the drain isn't blocked with old leaves and dirt, too.

It was the AC drainage hose that came disconnected under carpet on passenger side for our 2007 Matrix.

I have a 2009 matrix. I have water on passenger side. The air condition running also caused a hisss sound with every left turn as water on pipes. The carpet on driver side wet to but mostly passenger. Running from under dash. Today i turned off aircondition and ran air only. Now it stopped as if fuse blown. So looking for a mechanic. But suggestions needed.

The A/C condensation drain is clogged with debris.pull the carpet back on the passenger side and you will see the rubber hose coming from the reservoir to the floor. get a pan or a large cup and put it under the reservoir and pull the rubber hose off. if the water does not rush out,push a small piece of wire in the end of the reservoir and push it in/out until debris breaks loose and water comes out(a good bit of water). make sure the rubber hose is free of debris,re-install it on reservoir end and in the floor board!

I have the same problem but with a LOT of water in the rear passenger side floorboard. Also, quite a bit in the front but not nearly as much. There is probably 3 to 4 inches of water in the back. There is NO trace of water from any door panel or the top inside of the car. I checked the AC drain in the front but it is fine. I did not find a plugged drain at the bottom of the windshield cowling. I poured 1/2 gallon of water there and it didn't add to the water. I am stumped. 2003 Toyota Matrix. No accidents, one owner (me).

A dirty sunroof gasket and dirty mating surface (of painted metal) will let water wick through past the otherwise fine gasket. Clean the whole sunroof area thoroughly.

Thanks Guru92TFG, I'll give that a try. Wouldn't I see some evidence of water up there, though? It's completely dry and probably hasn't been opened for at least ten years. Can I pour some water there and see if it doesn't go through?

Don’t have Matrix any more, so no more leaks!

how do you pull up the carpet on a toyota matrix? Im having this problem with my car

https://www.youtube.com/watch?v=qdux22XrlgA

Found this video...will try on my vehicle later...it is summer now and we have the AC running regularly...the water doesn't have a color or odor and there has been no significant rain: https://www.youtube.com/watch?v=y1C0GbYjErk

If the carpet is wet on the passenger side floor and it's not dripping water steady under the vehicle on the ground while running the A/C,then either the A/C condensation drain tube/reservoir is clogged up or the drain tube has been disconnected by accident with a foot and all the water/condensation is draining in the floor inside the vehicle! simple fix....

pull up carpet. (just yank it.... the screws will pop out but you can put them back in. Plastic, non strip type). find the hose from under the dash which runs out through a hole in the floor. pull it out and stick a hanger all the way up through the hole the hose was on. be ready.... gonna FLOOD big time so have something to catch it even if it's a few towells. put it all back together and get a fan in there for an hour or two to dry everything. (DO THIS cuz the fuses ae all under there and they can rust). No more hiss... no more leak. STUPID TOYOTA engineering if you ask me. The car will run for ever but this sort of stuff is just not right. especially if you call your dealer. they'll offer to fix it for $4-500 or more.