Hi all

Been having issues with my 545i for a while, it drains the battery overnight. Put a new battery in a still the same, and even had an auto electrician look at it, and he could find no drain. After he went the car was left for 3days and started fine each day until the 4th, when there was no power. The only thing I did different that day was wash it.

Taking the battery out, I noticed some water the in the battery compartment, but not a huge amount.

I'm wondering if this has something to do with the drain, and where it could be coming from. The car has no sunroof, and the wheel well flooded before and previous owner had this fixed at bmw along with a new MPM module.

Any ideas as Im stumped

Thanks in advance.

 

I would focus on the water first. At least, if it is water and not fluid from the battery. Perhaps check the rubbers along the rear lid. White powder usually is used to determine how water travels.

Then, focus on the battery drain. Perhaps it causes some short circuits which lead to drain, but not necessarily.

 

Just talc powder?

Anyone know how to remove the battery vent grills?

 

Mine suffered water intrusion from clogged sunroof drains. Without a sunroof, I could only think that a seal failure on the rear window or trunk is the culprit (or maybe the fuel spout plastic surround.) Talcum powder or flour sounds like a good solution to find out where its going.

Before I knew about the sunroof drain problem, I tracked down the water flow by discovering the padded "shield" over the fuse panel (above the battery tray) was damp. Same for the other side. I also noticed that the water intrusion (just after a car wash) was causing the red alarm LED in the rear view mirror to glow constantly rather than blink. Drying out the rear fuse panel fixed that problem.

In early L322 Range Rovers, water intruded through the tail lights. I suppose that might be another avenue to check. I have never had a German car that did not have an issue with water at some point. I hope you successfully track down the source.

 

See the seal of rear tail light.