How to Fix Water Leaks in Your Car (Don’t Wait Until It Rains!)

If you’ve noticed a peculiar odor in your car and puddles on the floor mats, there is but one explanation: you’ve got a leak. As a matter of fact, that odor may be a part of the car’s design, as some manufacturers use materials that emit an odor when they come into contact with water to warn car owners about leaks. So today, we’ll be talking about how to fix water leaks before the rain season.

Actually, making sure that your vehicle is waterproof is incredibly important all year round. After all, depending on the area where you live, you could be getting snow and rain throughout the fall and winter and storms in the spring and summer. Fortunately, there are simple ways to protect your car from water damage. By the end of this article, if you notice that some of these protections are missing from your car, I recommend that you fix that as soon as possible.

But before I tell you about how to waterproof your car, let’s talk about some of the weak spots you’ll need to pay attention to.

What to do if water leaks in your car when it rains .

The first thing you’ll need to do before you can start dealing with the problem is to find out where the water is coming from. Usually, there’ll be a few clues you may be able to follow:

  • Streaks on the dashboard or going down the doors. Even if they’re dry, you may see white marks where the water passed.
  • Puddles or stains where the water usually pools on the floor or even inside of the door compartments.
  • Rust going from the roof down the doors, possibly under the carpets and the floor mats.

In this case, rust would be the worst case scenario — but we’ll talk about some of the potential serious damage a bit later. For now, even if you haven’t found any of these clues, you may want to perform a leak test, just to be sure.

Actually, I’ve written about how you can find the source of a leak in my article on leaking windshields. If you missed it, you’re only going to need soap, water, and an air compressor hose (or the vehicle’s internal AC). Basically, you’ll want to pour the sudsy water along the seams of the car, then blast the same areas with air from the inside. If there’s a gap, the soap will start bubbling, and you’ll know which area you need to deal with.

However, that’s not even the only thing that could cause a leak! The water could also be coming from the heater core and clogged sunroof or air conditioner drains. Not to mention the doors and the sunroof itself. Still, the test I’ve mentioned should work on those too.

But other than preventing a few streaks and stains, why should you care about water leaking into your car? Let’s find out.

The Dangers of Water Damage in a Car

As you might have guessed, the one thing you need to really worry about is rust. Even though our cars are made to be able to take a bit of rain, the metal can wear down if it’s always wet. So if water is continuously pooling on the floor, you’re bound to see some rust.

However, you should be even more worried about the corrosion of the electrical components. If the water somehow gets to your car’s wires, you could be in real danger.

That’s why, if you notice rust or corrosion of any kind, you should go straight to your mechanic. And if your car was actually submerged — like if it was in a flood — you should immediately see a professional. They’ll be able to tell you whether the vehicle is salvageable at all.

However, if you’re working alone, and you run into a bit of rust, you don’t need to panic. Simply sand even the tiniest amounts of rust to prevent it from spreading, then seal the area. As long as you’re thorough, you should be able to prolong the period you can go without visiting a mechanic. Although, keep in mind that you will eventually have to face them if you do a bad job DIY-ing the rust away.

How to Fix the Causes of Water Leaks to Prevent Future Damage

Now that we’ve considered the possible causes and consequences of having water leaking into our cars, we know the gravity of the situation. So let’s see how you can waterproof your vehicle, starting at the top.

1. Roof Seams

First, let’s figure your roof situation. You can do the test I’ve told you about on the seams all around the roof. However, if you can see any bubbling or cracks in the paint along the sides, that’s where your leak is. Another pretty big clue will be if your roof is completely rusted over.

If you spot any rust near the roof, sand it, clean it with rubbing alcohol, and maybe even use some touch-up paint on top. Once again, if the damage is too extensive, you ought to take the car to a mechanic. They might even have to take out a chunk of the metal and replace it. I’m going to keep repeating this, but if any part of the car has too much rust on it, you’re better off getting it fixed than painting over it.

After you’ve taken care of the rust, you can continue on to the main event. Between most metal panels of your vehicle, you’ll see a rubber gasket that’s sealing the space. Usually, these rubber bits wear away faster than the metal itself. As I have mentioned in my windshield article, these areas tend to get leaks because the water that falls in these gaps expands as it turns to ice, thereby creating tiny gaps.

The only way to deal with them is to apply sealant over them since you won’t be able to replace the rubber. In fact, you’re going to need sealant for most of the automotive waterproofing projects you undertake — so you might as well get a good one. You can read more about the best sealants and how to apply them in the link.

After you seal all around the roof, let the sealant cure and set completely. Then, you can test the area for leaks once again using the soap water technique or just by blasting it with a hose.

2. Sunroof Drain

Moving parts are often the biggest vulnerabilities of our vehicles. And although not all cars have sunroofs, those that do are at the biggest disadvantage during the wet season. Still, if you’re only having issues with the rubber gaskets around the perimeter of the sunroof, you’ll be able to fix it with a sealant.

On the other hand, if your sunroof doesn’t close properly, you should start with a good cleaning. It may just be a matter of dust and debris around the inside of the sunroof, making it difficult for the window to close properly.

The last possible cause of the leak will be the trickiest to solve, but you could still do it without the help of a mechanic. Sunroofs often have draining systems to prevent rainwater from ever getting into the vehicle. Even auto manufacturers know that leaving a hole on the roof is pretty risky, so they built in this failsafe. As far as I’m aware, getting someone to fix this for you would cost somewhere between $100–$150.

If you have an air compressor, you can use it to blow the gunk out of the drainage system. That should resolve the clog. If you don’t have an air compressor, a water hose might create a similar amount of pressure. Check out this video if you want to see where to access the drain.

Of course, if there’s a leak even after you’ve done that, your drain may have gotten disconnected somewhere along the way. If that happened, you may want to get your car to a mechanic.

3. Windshield Gaskets

Moving away from the roof, let’s talk about the windshield. As I’ve previously mentioned, I’ve already written about this issue. In fact, I had suggestions for several ways of dealing with it.

As always, you should start with eliminating the rust. Sanding, cleaning, and touching up the area with some paint should be fine. Or if the damage is too extensive, you can take it to a mechanic.

However, if it’s not, you can fix it with silicone, butyl, or urethane sealants. There are advantages and disadvantages to using all three types, as you can see in my article on preventing windshield leaks. I’ve linked to that article and my sealant recommendations in the text above. And of course, all of these tips would work on the rear windshield as well.

HOW TO STOP WINDSHIELD LEAKS

4. Door Seals

If you’ve traced the source of the leak back to one of the doors, there are still several areas that could be to blame.

For one, if the water is coming in from the edges, you could be having a problem with the seals. The doors on most cars are lined with a rubber seal, exactly like the one that goes along all of the other seams of the vehicle. However, since doors move, these strips of rubber are bound to have more wear than those along the roof.

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After the doors have been open and shut enough times, the rubber may start to peel or crack. Fortunately, fixing it is a breeze:

  • First, take the rubber off entirely, either along the one side where it started to peel or all around the door.
  • Clean up the area with rubbing alcohol to get rid of the adhesive and the dirt.
  • Peel off the protective layer covering your new rubber seal and start applying it wherever you need it.
  • Cut off the strip of rubber when you’ve covered the surface.

There’s really nothing to it — most drivers end up having to do this at some point or another anyway. Just make sure that the new seal you get is similar to the one you have. It shouldn’t hinder the door’s ability to close in any way, and it shouldn’t leave a gap. That would put you right back where you started.

On the other hand, the problem would be more complicated if the waterproof membrane inside the door itself started to let water seep through. This would require you to open the door and reseal the waterproof layer with tape, or try to replace it. However, this is really a job that’s better left to a professional.

5. Window Gaskets

Of course, doors also have another huge weakness — the windows. Usually, there is weatherstripping tape along the inside of the window frame. The glass itself moves up and down, wedged within this rubber tape, which in turn stops any water from coming in when the window is shut.

However, just like any other rubber product, it eventually starts to show signs of wear. The rubber can spread and shift a bit, allowing more space for rainwater to pass through. Additionally, on really old and run down cars, the rubber gaskets around the windows may also get loose and hang from the door.

Well, in that case, all you need is a bit of weatherstrip adhesive to glue the tape back on. If it hasn’t been damaged in any other way, it should still be effective against rain. But if it isn’t, you could try to take the gasket off entirely and clean the area with a spray cleaner.

While the cleaner is in the gap, you could help it along by making an improvised cotton swab. Then you can apply a replacement weatherstripping tape. Keep in mind that it would need to be sort of V-shaped though, since the rubber needs to hold the window. So it needs to be both on the inner and on the outer sides of the glass.

The rubber tape I linked to above should work, since it has that split down the middle. Although, if you’re afraid of improvising like this, by all means, go to your mechanic. Again, you’re going to be the one who’s going to have to explain it to them if you botch the job.

6. Heater Core Leaks

People who are used to driving old cars may be skeptical of this one, but it’s true! Heater cores are on the inside of the cabin in newer car models. So while the excess liquid might have drained under the car in older models, the coolant is now getting inside the cabin from the ventilation ducts.

If you’ve noticed liquid coming from the vents, this is surely the reason why. Believe me, you don’t want to let the coolant soak into your carpet and floor mat. Most of the time, you won’t even know it’s there until your floors have already rusted through. And by that point, you should just make peace with the fact that you’ll be Flintstoning it to work from now on.

And if the coolant is hot when it gets inside the cabin, you’ll have bigger problems to worry about. The liquid can get to about 200 degrees Fahrenheit, which will definitely steam up your cabin. It’ll also smell pretty funky too — for a good reason: it’s poisonous. In fact, if you smell something you suspect to be antifreeze, you should just leave the car immediately.

You can deal with a leak in the heater core in one of two ways:

  • You can replace the whole core or get someone to do it for you. Keep in mind that the core is probably going to be in a spot that’s fairly tricky to navigate. So if you’re not already familiar with the anatomy of your car, you should leave this to the experts.
  • You can try to seal the leak. If it’s a smaller leak, you can wait until your car is cold, then add a gasket sealer to the radiator. That would be easier than taking out the whole heater core.

7. Air Conditioning Drain

Just like the sunroof, your AC has a drain tube that gathers condensation and leads it away from the cabin. However, this tube can also get clogged or disconnect along the way. I even mentioned this as a possible culprit of water pooling in the car back in my windshield article.

Drive without the air conditioning for a while. That will show you whether the water is coming from the front windshield or the AC. If the water stops pooling, you’ll know that the AC was to blame. Now let’s see how you can fix it.

Well, if there’s a clog, you can start by finding the drain, which is usually under the car, near the front right tire. You can bend or squeeze the hose a bit to try to dislodge the clog. You might even try to insert a thin pick inside to get the gunk loose.

If it’s disconnected, you may be able to see that while you’re under the car. On the other hand, the tube may have gotten loose from the engine itself, which you’d see under the hood.

If you can’t figure it out yourself, you can always take it to a mechanic. After seeing the dangers that can come from having a coolant leak, a bit of AC condensation may not seem as dire. However, I’ll remind you that water can still cause the metal to rust. So getting a leak fixed as soon as you notice it is worth it either way.

More on Protecting Your Car from Water Leaks

Now you know exactly how to protect your car from water leaks. So go ahead and implement some of the tips I’ve talked about today.

Trust me, you’re going to want to do all of this before it starts raining. But if you’re not sure whether your car has a leak at all, you can refer back to the soap test I wrote about in my article about preventing windshield leaks.

On the other hand, if you know conclusively that there is serious water damage in your car, I wouldn’t touch it until a professional has taken a look. Especially if your car has been in a flood, the damage could be well beyond repair.

Still, there are plenty of instances of leaking you could easily fix yourself. Hopefully, this article has given you the tools and the confidence to do so. In the meantime, I recommend investing in a waterproof car cover if you can’t keep your car in a garage. That will protect it from prolonged exposure to the rain and the ice that could cause gaps and leaks.

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