How To Fix A Third Brake Light Water Leak — Ford Truck Technical Articles

How To Fix A Third Brake Light Water Leak - Ford Truck Technical Articles

How To Fix A Third Brake Light Water Leak

Many Ford trucks suffer from an unfortunate problem of leaking rainwater through the third brake light above the rear windshield. The foam rubber gasket around the brake light can dry, crack and consequently fail, causing water to enter the top of the cab. Or, other circumstances may deform the gasket causing an improper seal (as seen in this article).

For some, this can require expensive repairs to interior upholstery. Fortunately, detecting and fixing a leaky third brake light is a quick and inexpensive undertaking.

Fixing a Third Brake Light Water Leak

  • Skill level: Easy
  • Time Required: 30 Minutes
  • Tools Required: Philips-Head Screwdriver, Silicone (RTV or caulk
  • Other Useful Tools: Soapy Water, Hair Dryer

Detecting A Leak

If you think you might have a leak around your third brake light, there are a few quick signs you can look for: the inside of the windows may be foggy with condensation; the brake light itself may have condensation on the inside; the ceiling of the cab near the brake light, or the rear seat, may feel damp; or the inside of the back windshield may have water spots from drips running down.

Proactively checking for a leak before there are signs is easy and takes only a few minutes. Get a cup or spray bottle of soapy water, turn the interior fan to full blast, pour/spray the soapy water around the outside of the brake light and ensure you completely surround the light housing. Stand back and watch for a few minutes, if a large soap bubble forms or small ones rapidly bubble from one area, then you have a leak.

How To Fix A Third Brake Light Water Leak - Ford Truck Technical Articles

Fixing A Leak

The fix is simple and will only take about 20 minutes. Start by removing the two screws holding the brake light to the cab.

Lift the housing away and twist the light sockets out of the brake light housing. Examine the foam rubber gasket where you saw bubbles and you may see why it was leaking. In this case there used to be a satellite radio antenna mounted on the roof of the truck and the wire was fed through the gasket. After the antenna was removed, the gasket never reshaped and formed a seal. On many trucks the seal will have shrunk, causing a leak.

If you look inside the opening on the cab, you may see water marks and dust from where the light was leaking.

If the foam rubber gasket or the opening on the truck is wet, dry them off (a hair dryer works well for the gasket). Use silicone to make a new seal (black RTV was used in this example) — put a bead completely around the housing where the gasket sits (or should sit if it has pulled away).

Carefully put the lights sockets back into their seats in the housing and carefully fit the housing back to the body of the truck. Try not to disturb the silicone while mating it up to the body, and try not to move the light around too much after putting the light in place as this may spread the silicone too thin to make a good seal.

Reinstall the screws that hold the brake light in place and tighten them down (be careful not to over-tighten the screws so you do not crack the brake light housing). Let the silicone cure and dry according to the manufacturers instructions.

If you want to check the new seal, after the silicone has cured, pour or spray more soapy water around the brake light housing with the interior fans on full blast. Wait a few minutes and if no bubbles form, congratulations youve successfully sealed a leaky third brake light.

Article written by member postal302 .

Related lighting technical articles:

Leaking third brake light discussions in the F150 forum

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