Sunroofs: leaks, drains and glass replacement

Most sunroof problems in Ireland are not about broken glass at all. They are about water. A sunroof is not designed to be completely watertight at the seal; instead, water that gets past the seal runs into a channel around the opening and away through drain tubes, usually one at each corner, down through the pillars of the car.

Why sunroofs leak

• Blocked drain tubes. Leaves, pine needles and grit wash into the channel and block the drains. After an autumn of parking under trees this is the most common cause. Water then overflows into the headlining and runs down the pillars into the footwells.
• Detached or split drain tubes. Tubes can come off their outlets, so water drains inside the car instead of outside.
• A worn or misaligned seal. Seals harden with age and the glass panel can sit out of adjustment.
• Cracked glass or a failed bond on fixed panoramic roofs.

Checking the drains yourself

With the sunroof open, pour a small amount of water slowly into each corner of the channel and watch whether it drains away and appears under the car, usually behind the front wheels or near the sills. If it pools, the drain is blocked. Many owners clear drains with a length of flexible trimmer line pushed gently down the tube. Avoid compressed air at high pressure, which can blow the tube off its fitting inside the pillar.

Replacing sunroof glass

Sunroof and panoramic roof glass is usually toughened and often tinted or coated to reduce heat. Replacement glass must match the original mechanism exactly, so it is normally ordered by chassis number. The panel then has to be aligned so that it sits flush with the roof and seals evenly all round.

If you are not sure whether water is coming from the sunroof or the windscreen, see our guide to a leaking windscreen, which covers the scuttle drains and door seals as well.