what makes a car battery squirt out battery acid while car is operating?

Sounds like you have a dangerous situation here. One way for a battery to squirt out acid is if the vehicles alternator is overcharging. Should be charging below 14.5 volts. You can use a multi meter to check this yourself. Just start the engine and connect the meter to the two terminals on the battery. There are some local garages that may offer to do this check for you as a courtesy. The other way for this to happen is, if there is a crack in the battery. Look around the battery to see if it is installed properly with restraints and nothing jabbing into it. You may see crack around the positive and negative posts caused sometimes by over tightening of the clamp bolts.

Battery Replacment

Troubleshooting Battery Acid

In either case this in nothing to fool around with. I recommend (with your hands in protective gloves) removing the battery. Clean the engine compartment. And installing a new battery making sure the factory restraints are used. Battery acid is dangerous and poisonous(Do not take this lightly). You will need to neutralize any acid that has sprayed onto you engine components or the acid will ruin them permanently.

I am sure you are capable enough to do this but It is always best to let a professional do dangerous things like this to insure the proper precautions are taken.

battery squirts acid