When Does Rust Become a Problem for Your Windshield?

Car windshields can develop a slew of problems over the years. From fogged-up glass, scratches, and leaks, some of these are inevitable. However, it’s not known to many that rust can also be a problem in your windshield.

Technically, your windshield itself won’t develop rust. After all, it’s made of glass. However, leaks within the windshield glass will allow water to seep through and form rust in the interior. This will be a big problem if not addressed early on.

As water slopes underneath the seats, it will reach the rear floor area, where rust will start to form. When the moisture lingers, it will also harbor nasty molds and mildew.

The good news is that many car manufacturers use underpadding that will emit odor once it gets wet. This is why you shouldn’t dismiss malodors in your car if you want to prevent rust and molds.

What causes leaks in your windshield?

Pinhole gaps

When the windshield is improperly installed, there will be pinholes under the molding. These teeny-tiny holes will let rainwater enter the car. You won’t notice it right away, but the moisture can build up and form rust before you spot it.

Poor sealing

If the windshield has been replaced, it’s possible that the seal wasn’t applied well or it didn’t cure fully. Skips on the urethane seal are also possible culprits for the leak.

This is the reason why you should only trust professional windshield technicians for repairs or replacements. Make sure that they are AGSC-accredited to ensure the quality of their work.

Using silicone to fix holes

Whatever DIY remedy you’re using, never apply silicone to the windshield sealant. The silicone material will expand and contract when exposed to extreme temperatures. Such nature makes it ineffective in preventing leaks.

Also, proper sealants won’t adhere to silicone in case you want to re-seal it with the right material. If you want to fix a minor leak, it’s best to use a special seam-sealer.

How to tell if it’s time to replace the windshield seal

  • Test for leaks. The first thing you need to do is check for leaks. Use a low-pressure hose to shower your car. This will allow leaks to show up faster compared to high-pressure water. After a few minutes, check your car’s dashboard for signs of moisture.
  • Smell your car. If there’s an unpleasant smell inside your vehicle, it means there’s mold or mildew. Remember that molds proliferate with moisture. Most of the time, the smell will be concentrated on the floorboards and passenger area.
  • Look for dry-rot. Deep red marks located at the edge of the windshield glass indicates the formation of rust. Also, you’ll notice the seal starting to rot and crumble. These are signs that your vehicle is due for a seal replacement.


Rust will wreak havoc on your vehicle. Many car owners don’t realize that leaks on their windshields can cause such corrosion to form. So if you notice an unusual smell or damages on the windshield seal, you should consider a seal replacement. This will save your car from further damage and your pocket from expensive repairs.