Why is the battery leaking?

[awmccready]

It wasn't until last January, right after my transmission was replaced, that I noticed battery fluid eating paint off everything below the battery. I thought the shop just spilled the fluid accidentally, so I repainted the damaged area. A few weeks ago, I noticed the same thing starting again. The battery still performs as though nothing is wrong.

The most likely causes seem to be:
1. The alternator or a related control circuit is malfunctioning, for example, overcharging the battery.
2. The transmission shop cracked the case, which is now slowly leaking. However, I saw no cracks on the top or sides of the case. I haven't yet checked the bottom of the battery.

Are there any other potential causes that I missed? How can I best isolate the problem? I'd like to avoid just replacing parts. I've done that for other problems and sometimes that approach ends up being costly and time consuming without yielding a cure.

Advance Auto Parts has a free electrical testing service, so I will be heading there to see if I can eliminate any electrical stuff. Then I will check the bottom of the battery.

Ideas would be appreciated.

Thanks.

[sam333]

Spilled acid is coming from a crack in the case , battery overfilled , or alternator overcharging. If you think the trans shop cracked your battery, why didnt you pull it out and make them replace it? Besides making a huge mess ,a battery low on electrolyte can explode. Pull it out and check for cracks, but if its over 5 years old just replace it. If you don't find any obvious cracks make sure you test your charging system before installing a new battery.

[oopssorryy]

^Agreed^

I would get rid of the battery. I break apart batteries as a living, and let me tell you, you don't want that stuff in your engine bay, let alone you. If you get any on you rinse off for 5 minutes with salt water.

[Chris Crash]

Leaking battery = broken battery.

It doesn't matter the reason, just replace it.

[JohnGD]

Have a parts store do a check on the battery and charging system. Do you see where the acid is coming from? The vents? If so the acid is boiling inside. I'd agree that battery is most likely a goner.

Get an Autozone Duralast or Duralast Gold battery. These are excellent Johnson Controls batteries. So are the Interstates made by JCI.

[Zembonez]

Is the acid bubbling up from the top or just mysteriously appearing in the tray? I agree with the others if the tray is just getting wet, but if it's bubbling over, you may have an overcharging issue.

Either way, I'd bet a battery purchase is in your near future.

[oopssorryy]

If your boiling the acid you can not only damage the lead plates inside the battery, but hot acid is MUCH more dangerous than just acid. You should see what it does to spiders. You loosing acid which means you battery is on it's last legs. Once you loose enough you will just have some lead plates in you engine bay. Look into the overcharging issue, but i would bet that it's cracked somewhere.