How to fix water in your headlight or water in tail light

Why You Shouldn’t Drill a Hole in Your Headlight To Remove Water

Water or condensation inside a headlight is a common issue that many vehicle owners face. This problem not only detracts from the appearance of your vehicle but can also reduce the effectiveness of the headlights, making night driving less safe. If left unaddressed, water inside the headlight can lead to electrical issues, corrosion, and permanent damage to the headlight assembly. Fortunately, removing water from a headlight and preventing it from happening again is a relatively straightforward process. This article outlines the steps to remove water from your headlight and offers tips on how to prevent it from reoccurring.

Understanding the Causes of Water in Headlights

Broken Seals: The headlight assembly is designed to be sealed to prevent moisture from entering. Over time, the seals around the headlight can deteriorate due to age, heat, or physical damage, allowing water to seep in.

Cracks or Damage: Physical damage to the headlight lens, such as cracks or chips, can create entry points for water. Even small cracks can allow moisture to enter, especially during rain or car washes.

Blocked Vents: Headlights are typically equipped with small vents to allow heat to escape and to prevent pressure buildup. If these vents become blocked or clogged, moisture can become trapped inside the headlight.

How to Remove Water from a Headlight

Do NOT drill a hole in the lens or headlight body to fix a water problem

If there’s water in the headlight or tail light, the lens-to-lamp body seal has failed. Drilling a hole in your headlight drains the water, but doesn’t fix the root problem. You need to fix the leak, not the symptom of the leak.

If you don’t fix the leak, water will continue to enter the headlight or tail light and that water can shatter the headlight bulb or tail light bulb. It can also corrode the bulb sockets and sometimes even corrode the headlight or tail light reflector.

Drilling a hole in the lens is not a fix.

1) Remove the Headlight Assembly— Once you have access, carefully remove the headlight assembly from the vehicle. Be mindful of any wiring harnesses or connectors attached to the headlight, and disconnect them as needed.

2) Remove the Headlight Bulb— After removing the headlight assembly, remove the bulb from the back of the headlight. This step is crucial because it allows air to circulate inside the headlight, helping to evaporate the moisture.

3) Drain the Water— If there is standing water inside the headlight, gently tilt the assembly to drain as much water as possible. Be careful not to damage the lens or any internal components while doing this.

4) Dry the Inside of the Headlight— Use a hair dryer (not a heat gun) set to a low temperature to blow warm air into the headlight through the bulb opening. Keep the dryer or heat gun at a safe distance to avoid melting or distorting the plastic lens. Or, if the weather is warm and sunny, you can place the headlight assembly in direct sunlight for several hours. The heat from the sun will help evaporate the moisture inside the headlight.

What product should be used to seal a leaking headlight or tail light?

If you’ve done an Internet search on this problem you’ve probably seen advice to use household silicone caulk. Wrong. Ordinary silicone caulk from a hardware or home center does not work well on the types of plastics used in your headlight or tail light.

It also doesn’t flow well into the gap between the lens and headlight body. Lastly, it’s not compatible with the urethane adhesives used at the factory to bond the lens to the headlight body.

Worse yet, if your first application of silicone doesn’t stop the leak, you’re screwed because silicone caulk does not stick to previously applied silicone caulk. So you can’t apply more.

You need a urethane sealant designed for the types of plastics used in headlights

Polyurethane sealants provide high strength after curing. Urethane sealant provides high adhesion to smooth surfaces and is impermeable to moisture, so it protects the headlight from its penetration and prevents fogging of the glass from the inside.

Urethane sealants can be used directly on the street if there is no garage. After curing, polyurethane is not affected by fuel, alcohol-containing liquids, road reagents, etc. There two urethane products work best.

3M PU 590. Polyurethane
Dow Corning 7091

How to reseal a headlight or a tail light

Pour out all the water and dry the interior and the breached seals
Remove any loose adhesive from the seam.
Clean the seam with a degreaser to ensure the best bond
Rinse off the degreaser, wipe, and let the area dry completely before applying urethane
Use a hair dryer to dry out the inside and outside of the headlight and heat it slightly before applying the adhesive (especially if the headlight is cold)
Apply urethane around the entire seam, not just the area where the leak occurred

Wait for the sealant to cure before taking the vehicle out into the sun.

Be aware there’s a difference between water and moisture in the headlight and taillight

All headlights must be able to breathe to handle the heat expansion and contraction. So, all headlights and most tail lights have a vent port to allow air in and out. Some of those ports have filters. The filter does double-duty by allowing air to move in and out of the light housing while also keeping bugs and spiders out of your headlight and tail light.

However, because air can move in an out, so can moisture. If you park your car on a humid night after using the headlights, the headlight assembly will be hot. As it cools, it will draw in humid air. By morning, that humid air can condense on the inside of the headlight lens. That is normal and you should not do anything to correct that. The condensation will simply evaporate as soon as you turn on the headlight.

If you’re concerned about condensation on the inside of the lens, turn on your headlights and wait about five minutes for them to heat up. You should notice a substantial drop in condensation on the inside of the lens. If the condensation is still there, you may have a leak.

©, 2023 Rick Muscoplat