Sometimes, when my Prius is off and locked, I hear on occasion what sounds like the brake pump running for a few seconds. This is not right after shutting down, but rather hours later. Is this a safety feature to make sure that the power brakes are always available, regardless of the state of the car? If this is normal operation, it's not suprising that the auxilliary battery can go dead in as little as two weeks.
ah heck. my husband told me what that was but i forgot. i THINK it's depressurizing and repressurizing the abs system for some kind of test. i'm sure someone who remembers will post a better answer than my vague memory :huh:
Yes, it's always enabled, and runs occasionally to keep pressure up even after the car's been off for a while. This is the reason that service information often says to remove both ABS MTR relays before working on the 12V power system with gear that can't supply full current to the pump motor. . There is some sort of bleed/repressurization cycle that automatically happens about a minute after the car is powered off. You can hear this as a sort of hiss, and then the pump runs for a while. After that it goes into the aforementioned pressure-maintenance mode. . _H*
I do believe that after the car is shut off the brake accumulator pump is powered by the ultra capacitor pack in the back of the car and not the 12 volt aux battery.
Thanks for the replies. When I'm showing the car to someone and the pump starts up, the person I'm with usually asked what's making that sound. I'm glad I can give them somewhat of an answer other than "I have no idea, the car has a mind of it's own"
On my 2006 Prius, warm engine water was pumped into a thermos tank right after shutdown. Then, on restart, the water was replaced into the engine to minimize the time that the engine took to warm up, saving a little gas.
