Check Your Battery Compartment
 

I was doing an obsessive/compulsive cleaning out of the trunk today (no, not to get rid of evidence of a crime) and after taking out the spare and associated attachments I got a look at the battery one normally doesn't get, and I also get a bit of an unpleasant surprise. In the left front corner of the battery, right around the vent tube, there was a pile of powdery material (dry) as well as some bare metal and rust where the paint was eaten away (see pic if it attaches).

I can't recall my high school chemistry (or college, for that matter) all that well, but I guess the stuff might be a salt product of an acid reaction. The strange thing is, though, I couldn't find any obvious crack in the battery or sign of seepage from a vent cap, so I don't know what the heck is going on. I do make it a point in the fall and in the spring to keep the cells topped up, but not to overflowing.

Anyway, my point is this will need some body shop attention, it's not an area to risk weakening, and I do suggest that you take a peek yourselves, pull out the spare and disconnect and pull out the battery (remember your radio code!) to see what's going on with your vee-hi-cule.

On my E36 I had sprayed the battery compartment with 3 coats of undercariage, it helped with any possible damage :dunno

heh i had the same problem...but it was due to Water seeping in.

yea i would do wat rooz said, b/c you really dont need to paint it for cosmetic issues, no one looks there, so just sand down the rust and spray it with undercoating, the only time you would need a body shop's expertise if there was a hole in the compartment

An update on this little story... I made the repairs, sanding down to bare metal (mostly), applying rust converter, priming, and painting (surprisingly enough, the $4.95 can of Dupli-Color Truck, Van, and SUV (perish the thought) spray paint matched remarkably well, not that the problem was in a visible area). Ditto the underside, except I hit that with some undercoating.

What's interesting is that while I had the battery out, I decided to top off the cells with distilled water, bringing the levels to the bottoms of the slots, which may have been a tad more than specified but I figured no harm done. I reinstall the battery, insert the vent tube through the grommet, and drive off to do some errands around town. Twenty minutes or so after getting back I notice a wet spot at the right rear, I look underneath, and sure enough the vent tube is practically peeing, leaving a cirlce of battery acid in the driveway about 12" in diameter, which I guess represents roughly the amount of water I had put in the battery. All this was a few days ago and I haven't noticed any subsequent "urination," but this was the first time I've ever noticed anything like this. Anyone know what's going on?