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Water Leak Found! What Is This? (Photo)


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Rainwater is getting in on the driver's side of the boot. As the car is on a slope on my driveway, the water runs under the back seat and into the footwells on the driver's side.

Car is drying out really well, and now I have found the leak, a towel in front of the back seat in the boot catches any future water ingress.

First photo is the driver's side of the boot: carpet up, storage bins removed and carpet trim on that side removed.


At the very top edge of the image is a black rubber seal that the wiring loom running upwards connects into.

This is seen better in the second photo. It is this seal that is leaking.


My best guess is that the wiring loom is for the rear light cluster. Either that or there is a leak higher up around the roof area (load rails). Outside chance that the wiring could be connected to the fuel flap?

I presume I should be taking the light cluster out and checking seals. If I want to reseal, will ordinary household silicone sealant do the job, or should I be buying special automotive stuff?

I don't want to just bung up the seal that the wiring loom is passing through - the water is still getting into the car and I'm just sending it somewhere else!

Many thanks,


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Remove you light unit and you'll see the two screw fixings, they look like a wall plug with a foam seal when removed.

The foam seal breaks down from being crushed by the light unit allowing water through, I think they were about 60p each when I had the same problem with my ST some 5 years ago.

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Thanks all!

I have finally gotten around to lifting the light cluster and I am still in doubt. Once off, the wiring could be traced through to the boot and it comes out higher up (and is an entirely different loom too.

Bit the bullet and pulled the grommet out that is leaking and it is the wiring for fuel flap lock.(The wire went forward towards the fuel flap).

What I dont understand is how so much water got into the car.

The only two possibilities I can think of are:

1) Fuel flap seal is failing and water than tracks along the wire and through the seal. I don't buy that.

2) The wiring seals for the light custer are at fault, but the water is not following the cluster wiring but finding another path which takes it to the other grommet.

When it comes to applying silcone to improves water tightness, I take it I am squezzing a huge gobbet of the stuff in the grommet to seal the "slashes" in the grommet so no water can get in? Or am I also applying it to the external circumference of the grommet so sealing the rubber and the metal bulkhead as well?

Many thanks,


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I wouldn't bother with a 'silicone' sealant if you go down that route, I would go for a polyurethane based sealant as it sticks well to just about everything and it won't leak again.
If it's good enough to seal cables/glands on a ship then it will do for a car I suspect!

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