Windshield Leaks When It Rains? Main Causes and Repair

Believe it or not, windshields are actually the cause of about 30% of automotive insurance claims. These parts of our cars are notoriously vulnerable. In fact, according to the Insurance Journal, about 80% of those windshield claims are about cracks along the edges of the glass.

I, for one, would hate for a faulty windshield to be the cause of water leaking into my car. So I thought that I should deal with the problem head-on.

If water gets into your car, there are a few clues you’ll be able to spot:

  • Discoloration trailing down from the dashboard and pooling on the ground.
  • Windows that get foggy too easily and won’t clear up.
  • A peculiar odor — which is actually a preventative measure many manufacturers put into their cars on purpose, to alert car owners about flooding.
  • Mold and mildew, which can be a serious health hazard.
  • Lastly, if you see rust, you definitely have a problem.

Still, if you’re vigilant, all of these problems will alert you to the existence of a leak. Then, you can go about fixing it by following the instructions in this article.

How to Stop Water from Leaking Into Your Car from the Windshield

Before I tell you how you can go about fixing the problem, though, you need to be able to identify exactly where the leak is coming from. But first, you need to understand why your windshield may be leaking at all.

Why Is Your Windshield Leaking?

To put it plainly, even though they’ve been getting better in recent years, windshields are still notoriously weak. One of their primary purposes is to support the frame of the car, thereby protecting the passengers inside. But, if it can’t even fend off a little rain, can we really expect any kind of protection from this layer of glass?

Honestly, if your windshield is leaking, it’s most likely not because of the glass at all, but the area around it. Before manufacturers moved on to other alternatives, they used to use rubber gaskets between the glass and car bodies. Once they realized that rubber could deteriorate at concerning speeds, they moved onto butyl tape.

While butyl is a considerable improvement over rubber, car manufacturers have recently made yet another switch. Urethane has proven to be much more effective at fusing the glass of the windshield with the metal frame of the car. So nowadays, there’s not as much concern about gaskets leaking on their own.

Another reason why water may get in through the windshield is if there are cracks in the glass itself. Or, rather, if the metal surrounding the windshield has gone rusty. These are unlikely scenarios, though, especially in comparison to this final one.

Really, the most plausible explanation for a leaking windshield is that your car has been damaged by ice. If your vehicle is often outside during the fall and winter months, it’s probably getting rained on a lot. The rain that gets into the gaskets between the windshield and the metal car frame expands as it freezes over. Then, the ice pushes the windshield and the metal away from each other, creating tiny cracks between the two.

On the other hand, your windshield may not be the cause of the leaks at all!

Where Is Your Windshield Leaking Water?

Naturally, the first thing you ought to do when you notice one of the clues I’ve mentioned above is to determine where the water is coming in from. Other possible culprits are the doors, the sunroof, or even your air conditioning unit. If you see water dripping under your car, it may be the latter.

On the other hand, if you occasionally feel water dripping on your head — well, then you can blame the sunroof. Finally, discoloration around the doors usually indicates them as the weak link.

However, even if you do find discoloration or pooling in a certain area, the area right above it may not be the true source. For example, discoloration near your doors may have gotten there because the rainwater had streamed down the dashboard from the windshield. Fortunately, there are pretty conclusive ways to test your windshield for vulnerabilities.

How to Find Where the Water Is Leaking From

Your first indication that something may be wrong with your windshield may have come as you were washing your car. If you noticed water rivulets inside your car after blasting your windshield with a hose, you could use that as a test.

Starting with a completely dry car, you can gently pour water around the edge of your windshield. Using a high-pressure water hose will actually only cause the water to bounce off the glass.

I’d say that your best bet is to slowly work from the bottom up in order to see exactly where the leak is coming from. After all, if you start from the top, the water will run downward anyway. So you won’t be able to pinpoint the location of the leak.

Still, an even better way to locate a leak involves soapy water and air. Here’s how it works:

  • Put some water and soap in a bottle and pour it all around the windshield. You can work in sections if you believe the soap is running down too fast or just use more soap.
  • Turn the heater blower in the car on high defrost and shut the car doors.
  • Or, if you want faster results than what you can achieve with the car’s internal AC, you can take an air compressor hose and point it at the edges of the windshield from within the car.
  • You should see the soap start to bubble on the outside of your windshield wherever there’s a crack.

Since I’m all about efficiency, I’d go the air compressor route. You’d be surprised at how many bubbles will start popping up at the compromised areas. Once you’ve found the leak, though, you’ll finally be able to fix it — so let’s get to it.

How to Repair Windshield Leaks

Now that we’ve found the source of the leak, how can you fix it? Well, it’s pretty simple, actually. It all boils down to cleaning the area and applying a window sealant.

Since I’ve found about three different types of effective windshield sealants, I’ll talk about each of them and recommend a few products as well. However, you can also check out more of my recommendations in another article. But before you can choose a window sealant, let’s talk about the cleanup.

First Deal With the Rust

As always, the first thing you want to do when you’re starting any project is clean the area you’re working on. In this case, you’ll want to dry off your car before you do anything. Once the car is dry, you can clean the area around the windshield and inside of the cracks with rubbing alcohol. If there’s no rust, then leave it at that.

However, if you’ve spotted rust on the metal frame around the glass, you may have bigger problems. After all, the windshield is supposed to be one of the things that protect you from impact. It can’t do that if the metal frame surrounding it is unsound. So you should probably take the car to a repair shop.

Essentially, they may take out the rusted part of the metal and replace it with a healthy part. You’re probably not that keen on doing that kind of thing on your own. Still, if you can’t get your car looked at by a professional, you can do your best to deal with the rust.

Just sand as much of the rust off and clean the area with rubbing alcohol again. Finally, to protect the metal and make it more aesthetically pleasing, you can cover it up with matching Automotive Touch-Up Paint. Let that set and cure, and you’ll be able to move on to the next step.

Before we get to work with the sealants, you may also want to put frog tape over the windshield glass and the surrounding metal. You only need to be able to access the gap between the glass and the metal.

Use Silicone Windshield Sealants

Once you have a clean and dry surface to work with, you can get right into the sealants. Some of the most popular types of sealants are silicone ones like this one from Gorilla.

They’re completely clear and very runny, making them ideal for plugging tiny cracks and creating a flexible seal. If the area is clean and you’ve laid down the frog tape, you can just pour some sealant into the gap.

Move it along the area by wiping a finger across it, and then wait about half an hour before removing the tape. The sealant should cure fully within a day, at which point you can test for leaks again. If any remain, reapply the silicone. If you want more information about windshield sealants and how to apply them, then follow the link.

However, I should also say that some people aren’t that keen on using silicone for this purpose. Because silicone stretches and contracts in extreme temperatures, having it on a car in hot or cold conditions may not be advisable.

Still, I’ve also seen many people who swear by it. So this decision seems to be the one that only you can make for your car, but it’s by no means your only option.

Apply a Butyl Windshield Sealant

If you don’t want to rely on silicone sealants, you may want to try a butyl sealant. However, you should keep in mind that any sealant would be hard to apply if you’ve already put silicone in the gap.

Still, the process is fairly similar, with the exception of the tools you’d be using. A butyl rubber sealant (like this one from C.R. Laurence) should be applied with a caulking gun. But that might actually make it more manageable than runny silicone.

The rest of the application process is much the same as it was for silicone. As long as the area is clean and dry beforehand, you’ll be good to go.

Use Urethane to Bond the Windshield to the Car Body

Your final choice is to use a urethane sealant. As I have mentioned at the beginning of this article, butyl and urethane are already the things car manufacturers use between the windshields and the car bodies. So it makes sense that they would be the perfect materials for fixing a leak, right?

This 3M urethane sealant essentially looks like glue, and it’s made by a reliable brand I’ve used before. The sealant comes in a tube with a sharp applicator tip that’s going to fit into the gap between the glass and the metal easily. Once again, the rest of the application process is much the same, so you should make sure that the area is clean before you apply urethane.

Prevent Future Windshield Leaks

So you see, a leaking windshield is really very easy to deal with. As long as you know the context and are working with the right tools, you should have it done within a day, even with allowances for the curing time.

Remember, your windshield is supposed to be just that — a shield to protect you from anything and everything. You’ve got enough to worry about when you’re driving on a rainy day. Even on a sunny day, a faulty windshield won’t give you adequate protection against the elements. And you certainly don’t need to deal with mold on top of everything else.

Ultimately, fixing a leaking windshield is something you’d be doing for your own health, as well as the safety of other passengers. So why not do so today, if all it’s going to take is 15 minutes of work and a day off the road?




Scroll to Top