I remember that my 2005 Prius had a short whirring noise when I shut it off, as some coolant fluid was moved around. But my 2010 Prius has been pretty quiet at shut-down, until recently (has it always been there, or now that it's cold weather?) I noticed there's a very faint whirring noise coming from the engine compartment at shut-down. It lasts for quite a while -- almost a minute, then stops. Anyone else heard something like this?
Sorry for butting in: does anyone know the cause of the whirring noise heard when you unlock and open the drivers door? It goes on for maybe 5 seconds. Some sort of fuel pressurizing? I think the same noise happens periodically while driving. The Owners Manual lists some noises and explanations, but as far as I can tell makes no mention of this.
It's the brake accumulator pump building pressure for the power brakes. The Prius can't use vacuum for brake assist, so it has an electrically powered pump. Tom
I've heard some such extended whirring post shutdown coming from what I thought was the underside of the vehicle, not from the engine compartment, though I may have misjudged the source. I have a little over 6K and did not notice this until either Oct. or Nov.
Oh hey (just waking up), to the OP, from page 22 of Owners Manual, maybe this: Approximately five hours after the hybrid system is turned off, you may hear sound coming from under the vehicle for several minutes. This is the sound of a fuel evaporation leakage check and, it does not indicate a malfunction. I first heard this when I happened to jack up the rear end, just to have a look-see, had me a little concerned, it was several hours after shutdown.
