Why Your Car Floor Gets Wet During Rain & How to Fix It

It’s an annoying sight: a water puddle sitting on your car floor, soaking your carpet, and not going anywhere. Unless someone dropped an open water bottle, chances are there’s a water leak somewhere in your car.

If your car floor gets wet when it rains, there might be a water leak in your car. The most common reasons are faulty door or window seals, blocked wiper or sunroof drains, and issues with the A/C. Locate the leak, dry out the floor, and fix the leak by unclogging drains or replacing rubber seals.

Water leaks are easy to notice, but pinpointing their source can be surprisingly hard. This guide will walk you through everything you have to do to get rid of a water leak and prevent it in the future.

Causes Behind Wet Car Floors When It Rains

Faulty Windshield Gaskets

One of the most common reasons for water getting into your car is windshield leaking. Car manufacturers used to put rubber between the glass and the car frame. The problem was that rubber can deteriorate very quickly.

Nowadays, cars use butyl tape instead of rubber. But if your car is old or has poor-quality materials, your windshields could still be leaking water.

Your windshield could also be damaged because of frozen water. Water expands when it freezes, so when rain gets inside the gaskets between glass and car frame and then freezes, it could cause damage to the windshield.

Blocked Wiper Cowl Drains

Another common reason for water leaking is blocked wiper cowl drains. It’s the piece at the base of the wiper arms with slots to let the water in. This water is collected in a tray and then expelled close to the rear of the front wheels.

If this mechanism is blocked at any point, water can build up in the wiper cowl drains and cause damage. Again, letting frozen water inside the windshield is the main risk. The drains could become blocked with snow, frozen water, or mud, either at the base or at the top of the conduct.

Clogged Sunroof Drains

Sunroof drains are often left for last when checking for this issue. But, in truth, sunroof drains are more prone to leaking than they seem. Water can get around the rubber seal, which is why they have a drainage system.

This drainage goes through the under-portion of the sunroof and down the A-pillar. Some drains continue down to the base of the vehicle, while others let the water out at some point of the front door frame. Sunroof drains can easily get clogged with leaves and dirt.

Air Conditioner Leaks

Drains caused by A/C leaking can be especially annoying. A few different things could be going wrong, and some of them are easier to fix than others.

The most straightforward cause is faulty seals, which can cause the evaporated water to leak out of your A/C and into the floor.

A more problematic reason is a clogged evaporator drain. That’s the conduct that drains the evaporated water out of your car. If this drain becomes plugged, water and moisture will start building up inside your air conditioner.

Eventually, that water will leak out of the A/C and cause puddles on the floor. Even worse, the water could damage the electrical systems inside the A/C.

It’s also possible that the evaporator core is leaking. Dirt and leaves can get inside your A/C, and if they get to the evaporator core, it could cause rusting and eventually water leaking.

Door Seal Leaks

If the leaking comes from the sides of the door, then it means there’s a problem with the door seal.

The most likely culprit here is deteriorated weatherstripping. Weatherstripping is the piece of rubber that goes around the border of the door frame.

Weatherstripping degrades naturally over time. Eventually, it will start letting in water and wind. It’s difficult to say exactly how much one will last since it depends on how well you maintain it.

Window Gaskets

Like car doors, windows are surrounded by weatherstripping that encloses the glass from both sides. It stops water and wind from getting in when the windows are shut.

Weatherstripping can degrade over time, and in the case of windows, it also has to contend with constant bending and rubbing. If the rubber shifts or spreads, it could cause a water leak. In some old cars, the weatherstripping can entirely come off the window frame.

Locating the Source of the Leak

The first thing you should do when you notice a water poodle on your car floor is to locate the source of the leak. Here are a few tricks you should keep in mind:

• See if it leaks when the A/C is on. If water starts to build up when the air conditioner is on, the issue is likely inside the A/C system. If you’re not sure, leave the A/C running for a while out of the rain and see what happens.
• Use a mix of water and soap to locate the leak. If the leak is coming from the windshield, here’s an effective way to locate the fault.

Make a soap and water mix and pour it all around the windshield. Pour it gently and start working from the bottom. Add more soap if the liquid is traveling too fast to notice anything.

Take an air compressor or a can of compressed air and blow around the edges of the windshield. Wherever the liquid starts bubbling up, it can indicate there’s a leak. Alternatively, you can turn on the heater blower inside the car at maximum, but using an air compressor will be faster.

• Was your car sloped? If the leak only happens when the car is on a slope, chances are the leak is coming from a faulty door seal.
• Pour water on your sunroof and wiper cowl drains. Both mechanisms should let the water out through the bottom of your car. In the case of sunroof drains, there are usually four exit points, one behind each front tire wheel well. In the case of wiper drains, it’s usually at the rear of the front wheels.

Pour water onto one of the drains and check if water comes out at the other end. Then check the other one. This should tell you if the problem is there or somewhere else.

How to Stop Your Car From Leaking in the Rain

Now that you’ve located the leak, you can move on to fixing the leak. Let’s see what you should do depending on the issue that you’re having:

Faulty Windshield Gaskets

1. Find the exact location of the leak in your windshield gaskets. You can use methods from the previous section.
2. Get a windshield sealant. It can be silicone, butyl, or urethane. Permatex Windshield and Glass Sealer is very effective at forming a resistant seal.
3. Apply sealant on the leak. Make sure the sealant gets underneath the seal.

If there are several leaks, it might be a good idea to go through a more thorough process:

1. Remove the exterior trim of your windshield —that is, the seal.
2. Use an adhesive remover like paint thinner to clean the area around the seal.
3. Apply sealant to the windshield and reinstall it.
4. If the windshield seal deteriorates, you should consider installing a new one.

Blocked Wiper Cowl Drains

1. Pop your hood and locate the wiper cowl drain. It should be easy to see.
2. Remove the windshield wipers and cowl. After unscrewing the wipers, you can use a crowbar to gently take them out. Next, unscrew the cowl (the panel underneath the wipers) and remove it.
3. Remove any leaves or dirt that’s clogging the drain. You can use your hand. These are often on the sides, right where the cowl starts going down.
4. Clean the cowl drains. You can take an air compressor and point it inside the drains. If there’s dirt that refuses to leave, you can use a straightened metal coat hanger to poke it out.
5. Reinstall the wipers and the cowl. Before doing that, do a little test to ensure the drain is working.

Clogged Sunroof Drains

1. Open the sunroof. It’s the easiest way of accessing the sunroof drains.
2. Clean the rubber seal. Sometimes, the issue is simply that dirt and dust around the seal stop the sunroof from closing properly. Even if that’s not the issue, take the chance to clean it. It will extend its lifespan and prevent other issues.
3. Locate the drain that’s leaking. This step will be easier if you already know where the water exits are because it can vary with each vehicle. It’s still a good idea to clean all of the drains, even those that aren’t clogged.
4. Use an air compressor to blow out the clog. Point an air compressor inside the drains. Hopefully, the clog should come through the other side. If you don’t have an air compressor, a water hose may do the job.

Air Conditioner Leaks

Depending on the issue with your A/C, you’ll need to follow a different procedure. If there’s a clog in your A/C drain, follow these steps:

1. Park the car on a flat surface. Make sure to turn off your HVAC system.
2. Get a thin, stiff wire brush. If you don’t have one, you can take some wire, straighten it out and bend it at one end to make a hook.
3. Find the AC drain line. Most AC drain lines are located outside, close to the condenser unit. You may need to get underneath the car. Use jack stands if necessary.
4. Push the brush or wire into the end of the drain line without forcing it. Use it to take out any clogs you can reach from there. If you meet resistance, try to turn the brush or wire instead of just pushing.
5. Allow water to drain out of the line. This should get rid of any clogs near the end of the drain line. But if your clog is further up, check the next step.
6. Put a wet/dry vacuum at the end of the drain line. Seal it around with duct tape and run it for around a minute.

If the rubber seals of your A/C are damaged, you’ll probably have to replace them. It shouldn’t be too costly, and you can even install them yourself.

If the leak comes from the evaporator core, there’s no way around it: you’ll have to buy a new one. Talk to your mechanic about choosing the part and installing it.

Door Seal Leaks

1. Get a new rubber seal for your car doors. Try to make it similar to the one you already have. Make sure it’s compatible with your car model.
2. Remove the rubber seal. You probably won’t need any special tools.
3. Use alcohol to clean up the area and remove the adhesive. This process will make it easier for the new rubber seal to take hold.
4. Peel off the protective layer of your new rubber seal and apply it. Cut off the rubber strip once you cover the whole area.

Window Gaskets

If the rubber seal around a window comes loose, you can simply apply adhesive and stick it in place. This 3M Weatherstrip and Gasket Adhesive should be enough for most situations.

If the rubber is too deteriorated, then you’ll want to buy a new weatherstrip and apply it just as you would do with a door strip.

Make Sure You Dry Out a Wet Floor

Now that everything is fixed, all that’s left is drying out your wet car floor. If your car isn’t too wet or you don’t have time to do anything too complicated, do this:

1. Remove as much water as you can. A wet/dry vacuum can be very effective. Otherwise, use towels.
2. Put a fan blowing across your car. Open the doors on both sides of where water built up. Position a fan so that the air blows across the car floor and seats and comes out through the other side.
3. Leave the fan blowing for a day. It should get rid of most of the moisture.

If you want a deeper drying or got a lot of water inside your car, you’ll have to remove a few things. After removing the water, do the following:

1. Remove the seat of the place where the water has built up.
2. Remove the door seal trim that covers the door seal. Be careful with pulling out the wiring.
3. Partially remove the padding and hold it up with a pry bar or some other tool.

You may want to leave your car like this for at least one night. Adding the fan will make it even more thorough.

In Conclusion

If you notice a water leak in your car, you should get it fixed as soon as you can.

As the water builds up, it can cause rust, corrosion, and electrical damage, all of which are much harder to fix than the leak itself. The water will also bring harmful bacteria and mold to the interior of your car.

You can prevent water leaks from appearing by cleaning your car’s rubber seals regularly and keeping an eye on freezing rain. Water and an air compressor are enough to unclog a drain if done regularly.