Today: Fix for Bill's Leaky Sunroof?

Dear Car Talk

Dear Car Talk | Apr 15, 2014

Dear Tom and Ray:

I bought a 2006 Pontiac GTO about a year ago. After a considerable search, I found one with an aftermarket sunroof so the sun's rays could help heal the psoriasis problem on top of my head. When it rains, or when I go to the carwash, my car fills with water. It sounds like there is water sloshing around inside the passenger door. During heavy rain or while driving at high speeds on a wet freeway, the rear passenger floor gets absolutely soaked. The water then moves forward to "dampen" the front passenger floor. I know what you're going to say: "Replace/repair the sunroof first." OK, I will. But just in case, what else could it be? Thanks in advance for your help.

-- "Bathing Bill"

RAY: We can give you a couple of ideas, Bill.

TOM: That water that sounds like it's sloshing around in the passenger door? It could be sloshing around in your passenger door!

RAY: Water can get into the doors when it rains. That's why doors have drain holes at the bottom -- so the water can get out. But if your drain holes are plugged up with leaves, dirt or dead insect carcasses, water could be accumulating in there. And if a few inches of water builds up in the door, it easily could spill over onto the floor of the passenger compartment.

TOM: So have someone check the drain holes in your doors for you.

RAY: If the door drains are clear and there's no water in there, then you might check the sunroof's channels.

TOM: All of mine are set to HBO.

RAY: The water channels in your roof are supposed to drain away the water that gets in through the edges of the sunroof's opening.

TOM: There's no way to completely seal up the sunroof, since it's essentially a hole in your roof (although factory sunroofs tend to be better than aftermarket ones). So all sunroofs have channels that drain out whatever water does get in there.

RAY: There's one channel on each side of the car, and they run along the edge of the roof, and then down through the roof pillars and onto the ground. Your channels could be all plugged up.

TOM: The water that sounds like it's sloshing around in the passenger door could be sloshing around in the A pillar, which is the roof pillar that runs along the edge of your windshield.

RAY: And, like water in the door, if water builds up in your sunroof channels and has nowhere else to go, it looks for the easiest path to the ground -- which happens to be through your rear carpet.

TOM: Those channels can be checked and blown out with compressed air.

RAY: If that's not it, another thing to look at are the seals around the doors. If the weatherstripping is damaged or dried out and cracked, a surprising quantity of water can get into the car through the edges of the doors -- and that also could end up on the floor in back.

TOM: The same is true for bad molding around the front or rear windscreen.

RAY: And if it's none of those things, and you run out of ideas, think about just opening the sunroof when it rains. Maybe getting all that water right on your head can at least momentarily soothe that dry-skin issue?

TOM: Don't be offended by my brother, Bill. He just tries to look at every GTO as half-full (of water) instead of half-empty. I hope you find the source of the leak!

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One