1. Sun Roof Frame Seal
If no faults are immediately obvious, the point of entry can be through the gap between the top of the sunroof and the car roof itself. Although the sunroof will show no visible fault, the seal between the sun roof and the roof can dry out, allowing water to pass through.
Water can enter via other routes, but this should be visible, (unless your drain tubes are blocked or leaking).
The drip tray (bottom half) of the sunroof should not see large amounts of water unless there is a fault in the sunroof opening itself.
If you can see no visible fault and the amount of water entering the car via the roof started with a trickle and has been steadily increasing... The fault may well be this?
2. Drain Tube Fixing Points.
The drain tube fixing point (on a Land Rover) is a plastic molding fixed to the sunroof ‘drip tray’ with mastic. As with the sunroof seal, it can dry out, the seal is then broken and it leaks water onto the headlining. (Please note the water has to get in first in reasonable quantities before this may become noticeable).
In addition, the drain tube can:
- Break off.
- Become blocked.
- Be routed incorrectly.
If you can see no visible fault and the amount of water entering the car via the roof is in one particular area? Pour water in the drip tray to simulate a leak?
3. Rubber Seal.
If there is a problem with the rubber seal there should be obvious visible signs:
- Perished rubber.
- Failing to seal / Compression (you can check this by watching the rubber compress as the roof closes).
- Dirt, plant growth etc.
You would normally see a visible fault. The drain tubes should carry away the leaking water, unless it is excessive or the drain tubes are broken or blocked.
If someone has played around with the sunroof (e.g. the glass) and it is not fitted correctly, then this can lead to faults and then leaks.
Visual inspection for fit and finish?