How to Stop a Windshield Leak with Windshield Sealant

A leaking windshield can result in water damage, wind noise, and even electrical problems to your vehicle. If you see water drip inside or hear extra wind noise as you drive, glass sealant might be right for you. This guide will teach you how to find & choose the correct sealant and properly utilize it.

Why Does a Windshield Leak?

Leaks in windshields are normally caused by:

Broken or Worn Sealant:

Old urethane adhesive loses strength with time.

Defective Installation:

Gaps around the frame caused by poor installation.

Cracks or Chips:

Along the edge of the windshield.

Rust or Corrosion:

Around the windshield frame.

Leaks, left unfixed, can lead to mold, electrical shorts, and even structural damage.

Choosing the Right Windshield Sealant

Not all sealants are meant for use on windshields. What to look for in windshield sealant? The best windshield sealant should be:

Flexible – Must be able to withstand vibrations and temperature changes
Waterproof – Should keep water out
UV-Resistant – Must be capable of withstanding exposure to the sun without splitting
Adhesive – Should have good adherence on glass and metal

Best Types of Windshield Sealant

Polyurethane Windshield Sealant

The most sturdy option, the pro’s choice.

It will need some proper surface prep and cure time.

Best for long-term fixes.

Silicone-Based Sealant

Flexible and waterproof.

Easier to apply than polyurethane.

Might not have as long of a life in extreme conditions.

Butyl Rubber Sealant Tape

Great for sealing edges when installing windshields.

Good for temporary fixes.

How to Fix a Leaky Windshield

Step 1: Locate the Leak

Spray around the edges of your windshield with water while someone sits inside to spot drips.

Check common leak points:

Top corners
Along the edges
Near the rearview mirror

Step 2: Clean the Area

Loose dust, old sealant, and debris can be cleared away with a razor blade or plastic scraper.

Degrease the surface with isopropyl alcohol or a glass cleaner.

Step 3: Apply Windshield Sealant

For minor leaks, use a silicone-based sealant from a caulking gun.

For larger gaps, use polyurethane sealant (follow the manufacturer’s instructions).

Run a bead from the tube along the leak.

Step 4: Smooth and Cure

Press the sealant into gaps with a plastic tool or your finger (wearing gloves).

Allow to cure for 24-48 hours before coming in contact with water.

When to Seek Professional Help

If the leak remains after sealing, or if there are large cracks in the windshield or structural damage to it, have a professional auto-glass technician re-install or properly reseal.

Final Thoughts

Choosing the perfect windshield sealant will protect you from expensive repairs. For a small leak, you might be able to make it go away with the DIY fix of sealing around the base with silicone; for longer-term protection, polyurethane sealant is best. Proper surface prep and curing are essential for the best result.