How to Fix Leaky Truck Slider Windows

How to Fix Leaky Truck Slider Windows

The back slider windows on some older truck models have a tendency to leak. When water comes in around the glass, it can become a big problem for truck owners. The water can travel down the window track, wet the seats and interior of the truck, cause mold to grow in the carpet and leave it smelling musty.

The good news is that we have two simple fixes that should put a stop to the leaking around the back sliding window in your vehicle.

Clear the Drainage Channels Out

The first thing that you should do in order to fix a leaky rear sliding window is to clean out the drainage channel. If this is clogged and not draining properly, it can cause water to build up and leak into the cab of the truck.

To clear the drainage channels of the sliding window, you will need: needle nose pliers, at least one can of compressed air and a flat-head screwdriver. This method has two parts – inside and outside of the truck.


  1. From the outside of the truck, open the sliding window completely. You’ll probably need to sit in the bed of the truck to do this.
  2. Pull apart the two parts of the rubber gasket on either side of where the glass sit when in the closed position. In most truck models, there is a shallow drainage channel between these two pieces.
  3. Shine a flashlight into the channel. If there is something visibly blocking the drainage channel, such as pine needles or a small pebble, carefully use the pliers to take the object out.
  4. Then, use a can of compressed air to free the drainage channel of any dust and small bits of debris.


  1. Now, from the inside of the truck, locate the interior drain holes, or weep holes. These are also prone to clogging and are the potential cause for your leaking sliding window. In most trucks, the holes are located just in front of the glass, at the two bottom corners.
  2. Shut the sliding window completely; this will release the tension on one side of the automatic slider cable. You can use a flat-head screwdriver to gently push the slider cable mount to the far side and release the mechanism.
  3. Use a can of compressed air to clear the drainage hole. This will help clean out all the dust and build up that has been blocking the flow of water and condensation.
  4. Replace the slider cable mount.
  5. Open the sliding window completely to release the tension on the other side of the automatic slider cable. Use the flat-head screwdriver again release the mechanism.
  6. Repeat steps 3 and 4 on this side of the sliding window.

Because buildup will return to these drainage channels and holes over time, remember to clean them out regularly.

Reroute the Water Away from the Sliding Window

This method involves adding a rubber channel above the entire length of the back sliding window. The idea is that rain coming off the roof of the cab and down towards the sliding window will actually be diverted away from it. Most of the water will flow through the channel to the left and right sides of the truck, rather than down into it. This can make a significant difference in the amount of water falling down on the sliding window and should fix the leakage problem.

We recommend using 5/8″ tall black drip rail molding in high-quality, weather-resistant rubber with a 3m adhesive on the back. From the side, this molding has the profile of a ‘J’ channel. They charge by the foot for this molding at your local automotive supply and accessories store. You can also order this material online. The length should be enough to span the width of the entire rear window, not just the slider.

To add a molding that will reroute the water away from the slider, you will need: rubbing alcohol, a rag, and scissors.

  1. Wet the rag with the alcohol and use it to clean the surface of the glass where the new rubber molding will be mounted. It’s important to wipe down the window well because any small bits of dirt or dust left there will make the adhesive less effective when you mount the new window gasket. If the new gasket isn’t installed on a clean surface, it could create another leaky seal problem or cause it to move out of place completely over time.
  2. Wait a few minutes for the surface to dry thoroughly.
  3. Use scissors to cut the molding to the exact length that you want to use. Make at least two small marks on the rubber molding that you can use to center it in relation to the window on your truck. Try lining it up with your third brake light, antenna or the vertical seal around the glass.
  4. Remove the plastic cover from the molding’s adhesive strip. Then, line up the marks you made and stick it above the window.
  5. Press firmly all along the channel and smooth it down to ensure good adhesion.

Watch this helpful ‘how to’ video to see how this DIYer attached molding to fix his leaky truck window.

We also have some helpful tips for car owners looking to fix a leaky windshield.

Contact Anthony Volk for Car Glass Repair

Call the car glass experts at Anthony Volk today. We have three generations and over 20 years of experience in car glass repair and replacement. You can reach our office at (610) 436-9727 or simply request a quote online.

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Anthony Volk

Anthony Volk is a third generation auto glass installer born and raised in West Chester, PA. With over 20 years of personal auto glass experience he and his team will bring that experience to you.