Toyota Prius Forum banner
1 - 13 of 13 Posts

·
Registered
Joined
·
15 Posts
Discussion Starter · #1 ·
I just took delivery last week. When slowing down to a near stop or from highway speed to off-ramp speeds, I hear a short buzzing sound coming from the lower left of the front of the car. It sounds like something is winding up (or down). I sometimes hear the same sound when starting up from a full stop in slow acceleration (as into a parking lot). Is this normal? Thanks.
 

·
Registered
Joined
·
2,348 Posts
Redblue88 said:
I just took delivery last week. When slowing down to a near stop or from highway speed to off-ramp speeds, I hear a short buzzing sound coming from the lower left of the front of the car. It sounds like something is winding up (or down). I sometimes hear the same sound when starting up from a full stop in slow acceleration (as into a parking lot). Is this normal? Thanks.

Yep. It's normal. Now if you want to know all the different parts of the car that make these robotic noises, you can wait and let our tech skilled people expound.
 

·
Registered
Joined
·
7,161 Posts
Sounds like you are either hearing the motors themselves, or the inverter singing as it delivers current to the motors. The inverter works as a switching power supply, turning power transistors on and off rapidly to provide AC power to the motors. As the motors' required RPM changes, so does the frequency of the transistors turning on and off.
 

·
Registered
Joined
·
1,000 Posts
For reference, 'real' EV cars also tend to sound like that. It's all related to the electric motors.
 

·
Registered
Joined
·
4,873 Posts
You have an electric pump that cycles for the reservoir coolant, you have electric cooling fans that are intermittant, you have an electric hydraulic pump that operates whenever the brake pressure in the accumulator drops, you have electric inverters which make a noise. This synergy system makes lots of noises the standard car does not and unfortunately not too many people at Toyota dealerships have ever owned a Prius and are unfamiliar with the cars standard noises.
As every owner has posted previously and will for eternity, any noises from the front in a Prius "are normal."
Tis only when any under hood noises are accompanied by a set of idiot warning lights on the panel that things are not all that well!
 

·
Registered
Joined
·
6 Posts
Hi all,

I just purchased a new 2006 Prius this past weekend, and I have been hearing that sound as well! It happens for me when I apply the brakes (either at high speed or going slow) for the most part, although sometimes it does not make the noise. The noise itself sounds like a high-toned (almost difficult to hear) electronic noise when the brakes are pressed. Sounds like this is the Inverter? I am still getting used to all the noises that my Prius makes!

Thanks,
Mike
 

·
Registered
Joined
·
7,161 Posts
If it is high pitched, then it is probably the inverter operating its high power transistors to recoup the electrical energy back to the battery for regen braking. You might hear a similar sound when you take off.

If it were the accumulator compressor, it would be a lower pitch, almost the sound of an aquarium air pump.
 

·
Registered
Joined
·
6 Posts
Hi all,

Thanks for the info! Dan, it is a very high pitched tone, so you are probably right.. I am used to driving a Jeep (that made it's own set of noises), so these new noises are unfamiliar to me! I appreciate the info, and will not get worried when all of these noises occur.

Thanks again!

Mike

(ps. Dan - I am originally from the Tampa Bay area - St. Petersburg.. Go Bucs!)
 

·
Registered
Joined
·
7,161 Posts
Another common noise that is questioned is a whirring noise when turning. This would be the electric power steering gear noise. It is fairly faint, so you probably will only hear it in quiet drives with no radio, AC or ICE.

Yet another few common noises occur after powering off. First you might hear the coolant water valve change positions, then the coolant heat storage pump activate to store hot coolant from the engine into the thermos bottle, otherwise known as the Coolant Heat Storage tank. A minute or so you'll hear a hissing sound soon followed by a brrrr sound. The hissing is the brake system releasing all hydraulic pressure, then the pump restoring the pressure. This may be to self-bleed the system.

Another interesting noise I have heard is what seems to be the AC refrigerant settling when powered off. It sounds like a faint whisle.

One of these days I'll get a mic and record all these sounds.
 

·
Registered
Joined
·
7,161 Posts
Actually that's not suction. At least I don't think so. Considering that right after that the brake accumulator comes on, I believe it is the brake valves releasing brake pressure. I would think this is to help keep most of the hydraulics free of air bubbles.
 
1 - 13 of 13 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top