How to Fix Leaky Slider Windows on a Truck

Most older model pick up trucks have rear sliding glass windows, that have a tendency to leak, which can become an annoyance and a big problem for truck owners. When the window leaks, the water can travel down the track and get the seats and interior of the truck wet and if not dried completely, can cause mold to grow and the truck to smell musty.

The good news is that fixing these sliding windows is easier than you would think and as long as you catch the leak sooner rather than later, no major damage will be done.

Clear Drainage Channels

If the drainage channels on your windows are clogged, this could cause water to build up and leak into the truck. To clear these channels, all you will need is a pair of needle nose pliers, a flat-head screwdriver, a flashlight, and a can of compressed air.


  1. Open the sliding window completely.
  2. Pull apart the rubber gasket on either side of where the glass sits when it is in the closed position.
  3. Shine a flashlight into the channel to see if there is anything visibly blocking the drainage channel.
  4. If there is blockage in the drainage channel, use the can of compressed air to free the blockage.


  1. Located the drain holes (also called weep holes) on the interior of the window; These are typically located just in front of the glass on the bottom corners.
  2. Close the sliding window complete and use your flat-head screwdriver to push the slider cable mount to the side and release the mechanism.
  3. Use the can of compressed air to clear out the drainage hole to help remove dust and build up that is blocking the flow of water and condensation.
  4. Replace the slide cable mount.
  5. Open the sliding window completely to release the tension on the automatic slider cable and use the flat-head screwdriver to release the mechanism.
  6. Repeat steps 3 and 4 on this side of the window.

Reroute the Water Away from the Window

By adding a rubber channel above the length of the sliding window, the rain coming off the roof and down towards the window will be rerouted away from it. This will help reduce the water that falls down the sliding window and will fix the leakage problem.

Using a 5/8″ tall black drip rail molding with 3m adhesive on the back, adding the molding to your truck is extremely easy. Keep in mind that the length of the molding should span the entire width of the window, not just the sliding portion.

In order to add the molding to your window, you will need rubbing alcohol, a rag, and scissors.

  1. Wet the rag with rubbing alcohol and clean the surface of the glass where you will be mounting your rubber molding.
  2. Once the surface is dry, use your scissors to cut the molding to the length you need and make two small marks on the molding so you can easily center it on the window.
  3. Remove the plastic cover on the adhesive strip and line up the marks and stick the molding to the window.
  4. Press firmly along the molding and smooth it down to ensure it has good adhesion to the window.