Cleaning and testing your sunroof drains
Clogged drains are the most common cause of a wet interior, and the easiest thing to stay ahead of. Done gently, it takes a few minutes and no special skill. Done with the wrong tool, it can turn a small clog into a real repair, so the method matters.
How the drains work
Water that gets past the seal collects in a tray around the sunroof opening. Four drain tubes, one at each corner, carry it down through the pillars and out under the car. The front tubes usually exit near the front wheels or door sills; the rear tubes exit toward the back wheels or under the rear of the car. Leaves, pollen, and grit collect in these tubes over time, especially if you park under trees.
Signs a drain is clogged
- A damp or soaked footwell carpet, often on the passenger side
- Water in the trunk or spare wheel well
- Staining on the headliner, or drips near the interior light or mirror in heavy rain
- A musty smell from wet padding under the carpet
Drains rarely block completely. More often they slow down, so the cabin only gets wet during heavy rain when water comes in faster than the restricted tube can carry it away.
The two minute test
This is both how you find a clog and how you confirm you have cleared one.
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Open the roof and find the drain holes
With the glass open, look at the corners of the tray around the opening. The drain openings sit at or near the corners.
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Pour a little clean water into each corner
Slowly pour water (a cup is plenty) into each drain in turn. On a healthy drain it disappears quickly.
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Check that it runs out underneath
Have someone watch under the car, or look yourself, for water exiting cleanly near the wheels. Fast, clean flow means that drain is clear. Water that pools or trickles means that corner is partly blocked.
Clearing a clog, the safe way
If a drain is slow, clear it gently from the top with a soft, flexible drain brush, then run the water test again to confirm it flows. Patience does the work here, not force. A soft brush follows the bends of the tube and lifts debris without harming anything.
Both are popular online, and both can do real damage. We do not recommend either.
- Compressed air. The drain tubes are a push fit onto their fittings. Think of a balloon: enough pressure can rupture a tube or pop it off its fitting deep inside a pillar, where reaching it means removing trim or the headliner. A blast turns a clog into an interior leak.
- Weed trimmer line or wire. It is harder than the tube and the cut end is sharp. It can break through the side of a drain tube or push it off its fitting. A leak inside the pillar is far worse than the clog you started with.
A soft brush and plain water do the job without the risk.
How often
Twice a year is a good habit, ideally in spring and again in fall before the leaves come down. If you park under trees, check more often. It is a quick job, and staying ahead of it is far easier than drying out a carpet.
If every drain flows freely and water still gets in, the entry point is somewhere else. A shrunken seal, a windshield bond, a tail light gasket, or the air conditioning drain can all look like a sunroof leak. See Find your leak.