I noticed that when you park a Prius (and sometimes while you're driving), there's sort of a grindy sound that a note on the new car said was some vacuum reducing emissions. Does anyone have detail on what exactly the noise is, and what the vacuum (if that's what it is) does?
<div class='quotetop'>QUOTE(Boulder Bum @ May 13 2007, 06:36 PM) [snapback]441348[/snapback]</div> When you immediately turn the vehicle off? If that's the sound you are talking about my understanding is that it is a coolant transfer pump that moves hot engine coolant to a thermos for use during the next restart. There is also a vacuum 'test' that the fuel system does on occasion but I honestly can't remember hearing that as it seems to happen pretty randomly. A clicking or ratcheting sound can be associated with the brake accumulator pump and often occurs when slowing to a stop or just after stopping. Hope I got all that right! This car makes a bunch of odd noises
Yeah, a coworker asked about the whirling as we walked away from our vehicles. I did the best I could to explain the heated coolant and the thermos. It's a really cool system. If you are simply running some errands, the heated coolant helps bring the engine up to temp much faster.
The first sound is the coolant pump. I believe I read where the fuel vapor pump (or purge) can occur up to five hours after car has been sitting. There is also a battery vent fan, but I don't think it makes much noise. They do make a bunch of strange noises. :huh:
<div class='quotetop'>QUOTE(TonyPSchaefer @ May 13 2007, 10:58 PM) [snapback]441399[/snapback]</div> It's a HOT system. Tom <div class='quotetop'>QUOTE(Boulder Bum @ May 13 2007, 09:36 PM) [snapback]441348[/snapback]</div> This one sounds like the brake accumulator pump. Since the Prius can't use engine vacuum for power brakes, it has its own little pump to generate brake pressure. You will hear it running every once in a while when you press the brake pedal. Tom
Re: What's That Sound? When you immediately turn the vehicle off? If that's the sound you are talking about my understanding is that it is a coolant transfer pump that moves hot engine coolant to a thermos for use during the next restart. There is also a vacuum 'test' that the fuel system does on occasion but I honestly can't remember hearing that as it seems to happen pretty randomly. A clicking or ratcheting sound can be associated with the brake accumulator pump and often occurs when slowing to a stop or just after stopping. It' an interesting sound. Why would the Toyota engineers want to transfer coolant to a thermos? I could see transferring hot engine oil to a thermos to warm up the car faster in the winter time. Coolant can withstand extreme temperatures and probably has a minimal affect on keeping the vehicle coolant warm.
Re: What's That Sound? Am I correct that you hear the coolant transfer pump when you first power up the car and again when you power off?
