Heres the story, ran over a series of moderate potholes (road construction) this morning at around 25mph - rocky path, didn't want to slam on the brakes because the light just turned yellow and I didn't think I could stop in time. Anyway, after the rough bumps, I noticed the brake pump noise much more frequently then normal, about every 10 seconds - even when at a stoplight. Normally I think I hear the noise about every few presses of the brake pedal... Otherwise the brakes seemed to be fine... I checked the brake pump fluid reservoir after a few hours and it seemed to also be full... Other notes: temps were very low, about 37 degrees according to the outside air temp gauge. Something to be concerned about if the brake pump keeps going off more rapidly then before?
Check around underneath for anything "wet" looking. Normally the pump shouldn't run in the absence of actual brake *activity*, which uses the built-up pressure and then releases it back to the low- pressure reservoir side for another trip around. The solenoids are pretty good at holding that back when they're not open. . _H*
if the accumulator pump is seriously running more often there may be a problem with keeping pressure in the accumulator. it's happened before.
Hi Bob64, Something to check for would be a deformed (mashed is the more technical term ) brake line. These are steel tubes that are routed around the bottom of the car. Look for one that is round, then flat then round again. If your not getting a leak, slow flow through the small interior cross-section of a deformed brake line might be the cause of the extra pumping.
Braking while going over a pothole easily activates the ABS in a Prius. When that happens, it gets kicked out of regenerative braking and the hydraulic system takes over for a little while after. (A few minutes, maybe.) This means that each press of the brake pedal will deplete the vacuum reservoir and that will have to be recovered by running the pump that you hear. (This is odd to you because you probably don't brake hard enough to use the hydraulics on a normal basis other than the normal 8-0mph transition.) If this is what happened, it's perfectly normal Prius behavior. On the other hand if the pump is just running constantly while you cruise along then you probably have a vacuum leak somewhere or a control problem. A real brake fluid leak would cause a fantastic light show on your gauge cluster.
er yeah, I forgot to mention: I didn't use the brakes at all, until after - where I had to stop at the stop sign. Anyway, I've checked the garage that I've parked her in, and so far she isn't wet underneath. The frequency of the sound seems back to normal now too, so I guess it was just my imagination. False alarm Thanks all. I'll be sure to note any fantastic light shows in the vicinity of my gauge cluster.
