Water in Battery Bay

H

Hauntz4

New member
I have just purchased a 2013 Z4 and I noticed upon inspection of the battery bay that there was a small amount of water in there (no more than a quarter of an inch). I have sponged the majority of this up and following some heavy rainfall the battery compartment has got no more wet.

I know this sounds like a bit of a non-issue but I'm curious where the water came from the first place. The water was almost completely clear so it can't have been there too long and none of the carpet was wet.

My two theories are that either the water somehow got in there because I put the roof down when it was still wet so possibly some water could've got in there from the wet roof being stored in the boot or that a seal has gone on one of the lights but would I not see water on the carpets etc and in the other areas of the boot?

Hopefully someone can point me in the most likely direction so I can prevent it happening again.
 
At least 3 routes

Faulty seal around boot opening area..there's a complex seal that can get damaged and water then flows in the wrong direction

The rear ventilation vents in the boot to bumper area can be faulty

Poorly installed double lip seal on rear lights not correctly refitted
 
It’s also worth checking the small storage compartment on the left hand side of the battery and underneath the trim on the right hand side, check that the convertible roof module and electronic parking brake modules aren’t wet and also the parking distance control module if you have it.
IMG_8722.jpeg
 
I have noticed a small amount of condensation in the light so I'm assuming it's that, not scheduled any rain until the weekend so I'll get it all out then and check the fitting, thanks
 
Hauntz4 said:
I have noticed a small amount of condensation in the light so I'm assuming it's that, not scheduled any rain until the weekend so I'll get it all out then and check the fitting, thanks
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Not necessarily. It is common for light lenses to condensate internally a small amount.

Best bet is to completely dry the battery compartment, including the big lumps of sponge/foam around the roof pump. They can hold a lot of water (in fact they soak it up like a sponge) and can release it for a long time.

When you are happy it is completely dry do the tissue test (as per above) and monitor it. There is not necessarily a 'leak'.
Seen it many times where someone has spent ages looking for a leak because there is water in the battery compartment, only to never find one.

It is possible something as innocent as pressure washing the car could be the cause. It happens. The rubber seals are not always able to resist pressurised water. Many people will never go near the battery compartment until something goes wrong, so water can sit there for ages.
It is also possible one of your rubber seals had dried out. A good dose of silicone-based rubber care applied to ALL the seals is a very good idea (even if they are OK).
Also check the soft close on the bootlid is operating every time the boot is closed. They can sometimes need adjusting/ and or the cam not be triggered. If the soft close isn't firing (even occasionally), the boot seal will easily let in water.
 
Thanks for the advice, I've just applied a healthy dose of that Gummi stuff everyone recommends to all seals on the car and laid out tissue like suggested.

I did check the foam but it's bone dry so I'm not sure what's happened with that. I'll update once I find out where the leak is (if there is one).
 
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