What is that humming noise when power off?

Pumping coolant into the thermos, which holds hot coolant so the car warms up faster if you leave again soon, I guess...

 

I hear the same thing. Sounds like a dial tone.

 

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Wait a minute or so after it ends and you'll hear another noise.

 

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Indeed, that is the one consistent after shutdown noise. What everyone needs to realize is that the Prius is never really "off". In reading the owners manual, you can find where this car must be driven on a regular basis or it will run down its batteries.

The Bluetooth delinks several seconds after shutdown as well, so I assume that there are various shutdown operations going on after the power off is done.

 

Mikepaul is correct. Separate electric pump pumps coolant to the thermos to keep the coolant hot. If coolant in the thermos is hotter than the coolant in the engine then the pump will pump the coolant into the engine when it is started again. This warms the engine quicker and thus, lowers emissions. There is a very informative thread on this.

 

And about 1-5 minutes after that, the brake system releases all pressure from all lines (hear hissing sound), then followed by the hydraulic pump restoring pressure (motorboating sound).

 

Come on folks be honest.

When you shut off the Prius it connects to your home phone line and dials a number letting the car Gremlins know that it is now safe to come over and...

1. Put food crumbs on the floor and passenger seat.
2. Put undergarments under your seat (male or female depending on your sexual preference)
3. Either slightly fill or empty your gas tank to just play with your mind when it comes to figuring out your gas mileage
4. Set your NAV system to any other region but the one you live in.
5. Turn the radio volume all the way to max (especially if you ever smoked marijuana in the vehicle)
6. scratch your CDs so they skip
7. Hide your most recent car registration and insurance ID cards so they're never in the car when you're pulled over.

They're a busy lot!

 

RTFM? :mrgreen:

Ah, so the followup sound is the brake lines, not the immediate one you get which is the coolant system.

 

DanMan32, is that true? That's so...so...well...different! I always wondered what the 'extra' sounds were after the coolant pump noise. Way cool. Any ideas of why the brake pressure release, then restore? And where do you get this 'inside' info...or would you have to kill me if you divulged yer sources.

 

Just before the coolant pump runs, the valve rotates to connect the engine coolant circuit to the thermos bottle circuit.

The hissing sound I had taken some time to try and figure out. At first I though the hissing was coolant pressure releasing as the valve switched over. I had determined it was the brake as I knew the hydraulic pump sound (you can trigger it by operating the brakes), and the hissing was just before the hydraulic sound.

So then the first sounds have to be coolant. There were two sounds for that, on short and quieter motor sound, followed by a longer, bit louder motor sound. I already knew from New Car Features that the car stores the hot coolant on power off, and restores from thermos to engine on power on; on of the reasons for the 7 second delay for ICE to start. The other reason for the delay is to give you a chance to override for EV.

 

I never leave that stuff in the car. It's in the wallet. No sense allowing theives to have it, not that they could drive away the prius anyway without the fob. I don't understand why people leave them in the car. Those that say they do so others could drive the car, do you leave the fob in the car too?

 

or dialing up the feds to upload your most recent driving history from the black box.

 

Dan:

A lot of crooks have figured out the best way to break into a home is to break into a car at a mall parking lot. In the car will be the registration information, usually in the glove box.

The registration information has the street address, and now the crooks know that more likely than not, the house is empty. They can also use the information to commit Identity Theft.

So while you're sipping your coffee at Starbucks or browsing the displays, the crooks are in your home ransacking it. They usually have a "runner" keeping a discreet eye on your vehicle, so once you do return and discover the break-in, they use a cell phone to call the other crooks to give a head's-up.

At the very least, when you notice your car is broken into and the registration information is gone, better tell the cops your home address so they can check the house over. Never go straight to your home after such an incident.

Of course, if we had tough information privacy laws, and if we also routinely castrated burglars without anesthetics, it may really reduce the rate of such crimes.

Jay

 

Supports my comment.

 

Well, I have three cars, and

1) I'm not about to carry three sets of title & insurance papers around in my wallet, and

2) I'm much more likely to lose my wallet than have my car broken into.

I don't buy the identity theft argument. The insurance & registartion papers just have your name and address. BFD. There's lots of easier ways to get this information. I do not know, I'm just not that worried about it.

Most identity theft comes from stolen mail, not stolen cars.

 

Say you are just moving your Prius out of the driveway for another car to leave. If you go into EV mode, does the Prius still pump hot fluid from the thermos to the engine? Would being a faster draw on the EV switch save the heat for later usage, or will it happen anyway?

 

DanMan
the problem with not keeping your registration and insurance in the car is that you have to ALWAYS keep them with you. In CA if you get pulled over by a cop who didn't get the right lovin from the missis the night before he can have your car impounded on the spot and issue you a $250 ticket for no PROOF of insurance, and proving you had insurance only reduces the fine not eliminate it.

 

Maybe it is a dialtone.

 

If you have the papers in your wallet, and you have your wallet on you, you have your papers on you and can present to said cop.

Car->You->Wallet->Papers.

Seems safer than Car->Papers->unauthorized access.