Last week, I had a couple no start condition - no engine crank, no starter crank. After a few tries, car started to crank and finally started. I thought it was the battery so I opened up the battery compartment and found that the battery was surrounded by about 1/2" inches of water. I removed the battery and cleaned up the battery compartment with towels and hair dryer. Yesterday was a rainy day until this morning. I checked the battery compartment again and found water again the this area. I saw that water was coming into the compartment area via these vents:



This vent is snapped in from outside and is a bit lose.



Wet battery compartment area after yesterday rain:





Could this be a drain plugged up drain hose(s) around the battery compartment area ? I tried to find drain hoses in the compartment area from realoem.com but no luck.

Any help is appreciated.

Thanks,

 

The seal around the vent is leaking the rain water in to the battery area. If I were you, I'd remove the old vent, clean up the area, and install a new vent.

There is no drain/hole for the water sitting in the battery compartment. The battery vent is connected to the small hose and it is connected to the rear quarter panel. Water is not supposed to leak in to the battery area. If/when the water leaks in, no place for that water to go.

 

"The seal around the vent is leaking the rain water in to the battery area" - did you mean that these vents should be snapped into the opening very tight, not lose ? Mine is snapped into the vent opening loosely. I have another question then - should water be inside the rear quarter panel to start with (when raining outside or washing the car) ??

Thanks,

 

Just opened up the driver side trunk trim and also found water in that area too but not as much as the battery compartment. I have one question : does the vent install correctly - rubber flaps facing inside battery compartment. I saw that the vent in driver side also installed the same way as the battery compartment side - rubber flaps facing inside.

From realoem.com, the vent looks like to be installed with the vent flaps facing the rear quarter panels not inside the trunk. Is this correct ?

Can anyone tell me where are the roof drain hoses located ? I checked the rear seat footwell area inside the car, no water, very lucky.

Thanks,

 

My car has the same problem. There is one drain hole in my car, but you have to remove the plaster cap from the bottom of the battery compartment.

 

My vents appear to be facing the opposite direction as yours.

 

My 2008 535i vent seems to be a different version. Maybe you should try a newer type or turn around the one that is there now. Although I can't imagine why any previous owner would flip it around in the first place.
Either way the vent faces, probably won't make any difference since It doesn't sound right that water is filling the outside panel so high that water enters the vent in the first place. Something is blocked or damaged.
GL

 

Check the drain holes in the sunroof to make sure they are not clogged.

 

Your is the right way to install the vent. I just changed mine to the way same as yours. Now, only a couple drops of water coming in in the bottom of the vent when I opened the trunk which had water on it. I need to get a new seal for my vent in battery compartment. Driver side vent also installed in opposite way. I changed that back also. However, water coming into driver side wasn't thru the vent. It was above the vent where a control box sat.



I corrected the vent in driver side and passenger side (battery compartment)


This control box is taped to that area and water was coming from the corner behind it (next to the red wires).




I think that I need to remove the tail light assembly to see why water going into that area during rainy day.

Thanks,

 

I would like to do that but can you give a bit more details about the location of the drain holes in the sunroof ?

Thanks,