Question: I have a 2008 Chevrolet Pickup and water sometimes comes in from the headliner after it rains, but almost always comes in when I have it washed. I don't know if it's coming from the sunroof or the luggage rack.
Answer: The luggage rack supports are a possible source of water entry, but first check the sunroof. The sunroof weather strip is not a perfect seal. The sunroof opening is surrounded by a water channel. When water gets by the weather strip, it travels through the channel and runs out at four drain tubes located at each corner. The front tubes are routed down the windshield A-pillars, and the rear out the rear C-pillars. From there, the water drains harmlessly to the ground.
Get a bottle of water and perhaps a long narrow funnel. Open the sunroof and carefully pour the water into the channel, directing the water to one corner at a time. The water directed to the right front corner should hit the street below the right A-pillar; water at the right rear, below the right C-pillar; and so on. If the water does not reach the ground at one particular corner, look down into the channel and see if the water is backing up. If so, that tube is clogged or kinked. If that corner is not backing up, and the water is entering the truck, that tube is most likely disconnected and needs to be reinstalled.
Clogged drain tubes can often be cleared with compressed air, as long are you're careful to use low pressure and avoid blowing the tube off the channel connecting port. Disconnected tubes can usually be reinstalled by partially lowering the headliner enough to gain access to the connection. Kinked tubes can be more involved, and require interior trim panel removal to trace and repair. If the sunroof does not appear to be the source of the leak, partially lower the headliner and have someone hose down the top of the truck while inspecting the interior of the roof for an entry point.
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If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at email@example.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.
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