When fixing a 3rd brake light water leak, it's important to follow the process carefully to avoid wasting time and further damage to your vehicle. The 3rd brake light is the brake light above the windshield on many vehicles. When this leaks it can damage the inside of your car and the wiring that makes the light work. To fix it, use a simple process and get back on the road quickly.
1. Diagnose the Leak
If you've noticed condensation in the light housing, this is general evidence there is a leak in your third brake light. If you aren't sure of a leak, you need to diagnose it before you get started. You can do this by filling a spray bottle with soapy water and turning on the interior fan to high. Dump the water all around the outside of the brake light housing. If you notice large bubbles or condensation a few moments later, there is definitely a leak.
2. Remove the Brake Light Enclosure
Grab a screwdriver (generally a Phillips head) and remove the two screws on the light housing that hold it to the cab. Lift the housing away from the installation spot and twist the light bulbs to remove them from their sockets. Examine the bulbs to ensure they're in good working order and set them aside until re-installation. Examine the screws and screw holes to ensure there is no damage or stripping. Leaks can also occur when the screw holes are too large from stripping.
3. Examine All Parts
Examine the gasket and you will likely see the problem. If the gasket is misshaped, cracked, ripped or missing from a former antenna opening, you need to silicone seal (as per following instructions) or replace it. Look inside the opening and you will likely see water and rust damage as well.
4. Dry and Re-Seal
If anything is wet, use a hair dryer to dry the gasket and inside the housing opening. Use silicone to make a new seal around the housing. Squeeze a large bead of silicone completely around where the housing sits on the gasket. If it gets a little sloppy you can just wipe it away. Avoid getting any where wiring, bulbs and other components rest.
5. Reinstall the Light Housing
Insert the light bulbs back into their sockets and fit the housing back onto the cab of your vehicle. Don't move it around too much. You need it to line up right the first time and avoid moving it after it's reassembled to allow the silicone time to seal properly. Insert the screws and tighten. Don't over-tighten, as you can crack the housing.