I recently had a new battery put in my 1973 Super Beetle along with some other repairs. On the way home the car was perfect. Didn’t drive it for a couple of days. Took it out one night after dark a couple days later and hear a strange noise coming from the back of the car. Like a bubbling noise. Come to find out, some acid had come out of the battery. Took it to Auto Zone where they hooked it up to the battery tester and said the battery and everything else was fine.Hasn’t done it since except a barely noticeable amount of acid around the battery.
I had never put the back seat back into the car after repairs. The guy that worked on it has done so several times in the past and is excellent and has been working on Volkwagens since the 70’s. He’s one of the best around. He said the only thing he could think of would be the alternator, but that checked out fine at Auto Zone. What could have made that acid bubble out that one time and not since? Car is running fine now. Thank you!!

New battery was proll’y overfilled. Batteries bubble a bit as they charge. Some bubbled out until the battery could vent properly. Neutralize the battery acid that spilt with Arm & Hammer baking soda or you will have holes in the floor under the battery, if you don’t already. It is acid you know. Just mix up some water and and baking soda, lots of baking soda, and soak the area thoroughly