Funny sound shortly after takeoff

maybe your rotors are a little rusty, and sticking a bit when you brake to a stop. has it been humid?

 

Surely you jest, sir. You are asking a Texan "Has it been humid".

 

I wondered if there was something on the runway used for takeoff.

 

If it's on a hill, it's this:


You'll hear a small sound when the brake is automatically released by the car.

 

Record it sometime so you can play it next time you go in for service.

 

that makes even more sense with rusty rotors.

 

I can confirm that I experience the same thing that the original poster has reported. I often hear this sound after leaving the driveway while traveling uphill during a time period when the brakes are not in use. I also report it is a short, single chirp, only after first start and shortly after takeoff. Since it doesn't seem to be affecting the vehicle I have not taken any action such as taking it to the shop. It's hard to locate the sound but I always assumed it was a traction motor, but the pointer to hill control is an interesting theory

 

when you are stopped, pressing the brake very hard engages hill control with a signifying beep. when you proceed, there are no more sounds.

 

I have an uncle who used to entertain us as kids while driving by using his visors as flaps for takeoff and landing. I think the prime visors are too small for effective use as flaps though

 

Could it be...???

 

Ppongi, I'll pay a bit more attention to see if I hear it going downhill as well.

Bisco, thanks for the additional info on hill control (hard press and beep). I think this rules out hill control for my scenario.

Rrxing, unless that sound is mechanical (I presume it is electronic) I don't think so, although if I had to guess I hear the sound around 15mph.

I will try to gather more data. Rotor idea is interesting, my mechanical brakes don't get much of a workout. I had my ev range up to 42.4 a week or so ago

 

Yes Prius visors are too small. We have complained for years about the lack of visor extensions, some people have jury rigged homemade versions. Visor extensions would make them more effective blocking the sun from the side windows. And it would also increase the surface area of the visors which would help with takeoff and landing

 

Bisco, my 2014 Prius did that, but the Prime doesn't. You don't have to do anything special to activate it. Just hit the brake and if it senses the hill it will hold like the old version did, and no beep.

 

nice! toyota technology is really progressing.

 

Try it! You'll Like it!

 

Back to the OP... I think I've noticed the sound.
I don't usually start off in HV mode, so maybe why I didn't hear it before, or maybe because I have audio playing usually... but twice today starting off in HV mode: back out of the spot, speed up to parking lot speed and then I hear what could be described as a faint "chirp" coming from the driver's side rear area.

After that.. stoping and starting again in traffic you don't hear it.

This is on level ground.

I get the impression it's an actuator of some sort... maybe it's adjusting the gas cap or something. (You notice the gas cap turn after you turn it to click?)

I'm quite used to a Prius making strange sounds... It's doing things it needs to do...

 

Any chance it could be the auto door lock feature? I understand it engages at about 12 MPH or so. Doesn't sound like a chirp to me but worth a shot. I always wondered what that noise was when I first got my Prime.