5 months ago

How to Fix a Leaking Windshield Seal on Your Car or Truck

fix a leaking windshield

Since the invention of the first laminated glass windshield in 1904 by the French artist and chemist, Edouard Benedictus, these pieces of glass have been serving a major role in making cars safe and usable in any kind of weather. 

The main purpose of the windshield is to keep water and external air out of the car. Though it is impossible for water to penetrate the glass your windshield is made of, the seal that secures the windshield to the body of the car can sometimes give in, leading to water leaking into the car. 

In this post, we will go over how a windshield is attached to the car, why windshield seals leak, how windshield seal repair can be done at home if a leak does appear, and how to prevent it from happening in the future. In case you haven’t done so already, check out our guide on how to repair a chipped windshield at home if it has a small crack on it.

How is the Windshield Attached to the Car?

When the body of a car is made, an opening is left for the windshield. This opening is just a little bit larger than the dimensions of the windshield that is to be installed on the car. During the assembly process, the windshield is secured to the body of the car with the help of a rubber seal. There is a channel in the body of the car where the seal is seated, and then the windshield is placed inside a channel in the seal. 

This does two things:

  • It secures the windshield to the body of the car without having to drill any holes or use any screws. 
  • It seals the gap, making sure that no water or air can get past the seal.

What Causes Windshield Seals to Leak? 

Windshield seals are made of rubber. It is the perfect material for making these seals, but it does have its cons. Firstly, rubber has a lifespan, after which it becomes brittle. Secondly, any drop of water that makes its way into the channel where the rubber is seated on the body of the car remains there and can lead to rusting of the sheet metal under it. 

Windshield seal leaks can be caused by one of the following – 

  1. Deteriorated Gasket 

This is the most common cause of leaking windshields, which is seen mostly in older cars. The rubber gasket has aged and gets damaged, leading to water leaking into the car.

  1. Improper Sealing 

Screen replacement or any other repair in which the gasket is not replaced correctly can lead to water leaking into the car through the seal.

  1. Rusted Windshield Seal Channel

Water entering the space between the windshield gasket and the sheet metal of the car can result in rust eating away the sheet metal. The result will be a leaking windshield seal.

The key indication of a leaking windshield is water on the floor or dashboard of the car if you drive or park it in the rain. However, it’s important to make sure that you know what the problem is before resealing the windshield on your car.

How to Diagnose a Leaking Windshield?

This might sound like a daunting task, so we put together three ways to detect the problem if you have water leaking into the car from the windshield.

Wind Test 

If you are suspecting a water leak after a windshield replacement but you are not sure, a wind test is the best way. Simply, close all the windows of the car and drive it to the highway. Turn off any music and drive the car at more than 100km/h. If you hear a sharp whistling noise while going at highway speeds, there is a leak somewhere in the windshield seal or the door seals.

Shower Test

Once you have confirmed that there is a leak, the next step is to pinpoint the location of the leak. The shower test is the simplest way to do so. Close  the doors and windows of the car and shower it with water. Make sure to use low pressure and soak the entire car. Step inside the car and thoroughly inspect all seals. You can very easily detect the water coming into the car if there is a leak.

Soap Test 

Sometimes, when the leak is too small, the shower test might not be enough to detect it. In this case, the soap test is helpful. Mix some water with soap and apply it to the seal you suspect is leaking. While the surface is still wet, make sure all of the car doors are shut, turn on the heater at full power and direct the airflow towards the windshield. Now you need to inspect the seal from the outside. You will notice bubbles of soap water forming where there is a leak. 

How to Fix a Leaking Windshield?

The next step is to seal the leak. It might sound difficult but as a matter of fact, sealing a leaking windshield is even easier than repairing a cracked bumper. Here’s how you can do it:

Use a Windshield Seam Sealer for Pinholes 

If the leak is too small to be detected in a shower test and only appears in the soap test, you can use a windshield seam sealer to fix it. These come in the form of a tube and are very inexpensive. 

  • Clean the area where the leak is located. 
  • Inspect the leak closely and mark the exact spot.
  • Pry the seal up and squeeze an adequate amount of the sealer underneath the seal. 
  • Press on it lightly and wait for a couple of minutes for the sealer to cure.

Use Pliable Sealant for Improper Seals

If the leak is bigger or a piece of the seal is missing, the seam sealer might not be enough to fix it. In such a case, you need to use a pliable sealant.

  • Clean the area where the leak is. 
  • Apply the sealer on the leak/missing part of the gasket. 
  • Allow it to cure for a couple of minutes. 
  • Repeat the water test and soap test to make sure the leak has been sealed entirely. 
  • If the leak is still there, apply the sealant again. 

Use Metal Filler to Fix Rusted Sheet Metal 

If the problem is not with the rubber gasket and rather the sheet metal on which it is installed, you’ll need to use a metal filler.  

  • Mix the metal filler according to the instructions. 
  • Apply the filler on the affected area of the windshield.
  • Let it cure for the specified time, and then repeat the water and soap tests to make sure it is properly sealed. 

How to Prevent Windshield Gasket Leaks?

If you take good care of the rubber gasket, leaks will not form.  

  • Use a rubber protector on the seal when you wash the car. It will increase the service life of the gasket. 
  • Do not use harsh chemicals to wash the screen; they react with and weaken the rubber gasket.
  • If you have to get windshield seal replacement, try to go to a reputable workshop so that there are no chances of a leak.

Disclaimer: If you have limited knowledge of cars, consult a mechanic instead of trying to rectify the problem on your own.

Windshield Leak Repair | Frequently Asked Questions 

How difficult is it to seal a windshield leak?

It is not difficult at all to seal a windshield leak. It just takes a sealant and half an hour of your time to seal a leak in the windshield gasket.

How do I find a leak in my windshield?

Spray the windshield with water and look for any water leaking into the car from the place where the windshield is secured to the body of the car. 

How much does it cost to reseal a windshield?

Resealing a windshield is  fairly inexpensive, you’ll need a sealant which normally costs around $50 or less.

What causes the windshield to leak?

Windshield leaks are caused by a worn-out gasket, improperly installed seals, or a rusted body panel in the area where the windshield is secured to the car.

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