funny noise when braking at slow speeds

pmanza · 09-04-2007, 12:30 PM

Hi everyone, I just got my beautiful new Silver Pine Mica Prius (Fern) on Friday, and already have a couple of questions.

1- There is a funny sound when braking at slow speeds, only lasts for a few seconds, also sometimes happens when accelerating at slow speeds. I can't quite describe it, it isn't a buzzing sound, and not quite a whine either, somewhere in-between. Is this normal, and what is it?

2 - already have rattling left air vent. Has anyone had success with Toyota stopping the noise, or anything I can do? I hate to be smacking my poor cars dashboard when she is brand new!

So far, love my car!

Thanks for any input.
Peggy (Fernsmom)

bredekamp · 09-09-2007, 12:35 PM

<div class='quotetop'>QUOTE(fernsmom @ Sep 4 2007, 06:30 PM) [snapback]506792[/snapback]</div>

Quote:

Hi everyone, I just got my beautiful new Silver Pine Mica Prius (Fern) on Friday, and already have a couple of questions.

1- There is a funny sound when braking at slow speeds, only lasts for a few seconds, also sometimes happens when accelerating at slow speeds. I can't quite describe it, it isn't a buzzing sound, and not quite a whine either, somewhere in-between. Is this normal, and what is it?

2 - already have rattling left air vent. Has anyone had success with Toyota stopping the noise, or anything I can do? I hate to be smacking my poor cars dashboard when she is brand new!

So far, love my car!

Thanks for any input.
Peggy (Fernsmom)
[/b]

Question 1: The buzzing/whining is normal. If you can hear it, your ears are very good 'cause it's very subtle. Remember when you brake, the electric motors work like generators and put electricity back into the battery. There is a silver box under your bonnet with a Hybrid Synergy Drive logo on it. That's called an inverter. It's job is to convert one voltage into another by using high frequency on/off switching of transistors. What you're hearing is the high frequency waveform that controls the switching of those transistors. When you brake, the inverter has to carefully regulate the current being dumped back into the battery by controlling how fast it switches. That's why you can sometimes hear the frequency of the whining/buzzing change.

check out my site: http://www.myprius.co.za/Prius_inverter.htm

Questions 2: never had that problem...

qbee42 · 09-09-2007, 01:58 PM

There is also a brake accumulator pump which makes a little buzzing sound when it runs. It builds pressure for the power brakes, since the Prius cannot use engine power like normal cars. The brake accumulator pump runs about every third time you press on the brake pedal (on the average).

Tom

leachboy · 09-09-2007, 07:47 PM

Thanks to the original poster and everyone who replied. I just got a prius last friday and I was wondering about that sound as well.

qbee42 · 09-09-2007, 08:00 PM

<div class='quotetop'>QUOTE(leachboy @ Sep 9 2007, 07:47 PM) [snapback]509756[/snapback]</div>

Quote:

Thanks to the original poster and everyone who replied. I just got a prius last friday and I was wondering about that sound as well.
[/b]

It's the most common question I answer.

Tom

SebMike · 09-13-2007, 03:58 PM

On item 2, the rattling left air vent, I had a similar problem. I kept taking the silver plastic assembly on and off trying to figure out the problem, and I think I finally made it go away.

Pulling that plastic assembly off is kind of tricky because it's a fairly large assembly with several retention clips that attach to the dash assembly. I've cracked a few plastic pieces here and there taking it on and off too many times, so be careful...never fun to mar a new car, right?

Regardless, in my case, there were several yellow plastic clips that attach to the silver assembly. These clips kind of 'float' on the silver assembly when in place, which allows them to align and contract/expand to provide retention when inserted into the dash assembly. I found that by taking the yellow clips off and putting a few layers of tape (i.e. Scotch tape) to make the tip of the fin that the yellow clips attached to a little thicker, it cut down on the amount of 'float' for those clips. After re-inserting, my rattles went away.

At least in my case, there was "too much" play between the yellow plastic clips and the fins they attach to on the vent assembly. Putting the tape in took away alot of the play and also the associated rattle.

Hope that works out to be your issue and this helps...

Mike

SebMike · 09-13-2007, 03:58 PM

On item 2, the rattling left air vent, I had a similar problem. I kept taking the silver plastic assembly on and off trying to figure out the problem, and I think I finally made it go away.

Pulling that plastic assembly off is kind of tricky because it's a fairly large assembly with several retention clips that attach to the dash assembly. I've cracked a few plastic pieces here and there taking it on and off too many times, so be careful...never fun to mar a new car, right?

Regardless, in my case, there were several yellow plastic clips that attach to the silver assembly. These clips kind of 'float' on the silver assembly when in place, which allows them to align and contract/expand to provide retention when inserted into the dash assembly. I found that by taking the yellow clips off and putting a few layers of tape (i.e. Scotch tape) to make the tip of the fin that the yellow clips attached to a little thicker, it cut down on the amount of 'float' for those clips. After re-inserting, my rattles went away.

At least in my case, there was "too much" play between the yellow plastic clips and the fins they attach to on the vent assembly. Putting the tape in took away alot of the play and also the associated rattle.

Hope that works out to be your issue and this helps...

Mike

pmanza · 09-13-2007, 06:59 PM

Thanks everyone for your replies. I won't worry about the buzzing noise under the hood unless it gets real loud or consistent. The vent rattle has gone away for now, I suspect it will be one of those on again, off again things.

So far, I love my car. Its funny, I just wrote up a review on Edmunds, and my list of things to improve was was longer than the list of favorite features (surprised myself there), yet I still love the car. Go figure. Most of the suggested improvements were just little niggles though.

Fernsmom

pmanza · 09-13-2007, 06:59 PM

Thanks everyone for your replies. I won't worry about the buzzing noise under the hood unless it gets real loud or consistent. The vent rattle has gone away for now, I suspect it will be one of those on again, off again things.

So far, I love my car. Its funny, I just wrote up a review on Edmunds, and my list of things to improve was was longer than the list of favorite features (surprised myself there), yet I still love the car. Go figure. Most of the suggested improvements were just little niggles though.

Fernsmom

bredekamp · 09-15-2007, 04:46 PM

I was wondering about the rattle reported by many of our US friends....could this be an issue with the Left Hand Drive dashboard?

Anybody from RHD countries have similar rattles?

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09-04-2007, 12:30 PM	#1
pmanza Fernsmom Join Date: Sep 2007 Location: Sacramento Posts: 92 My Car: 2007 Prius Package: #4 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Hi everyone, I just got my beautiful new Silver Pine Mica Prius (Fern) on Friday, and already have a couple of questions. 1- There is a funny sound when braking at slow speeds, only lasts for a few seconds, also sometimes happens when accelerating at slow speeds. I can't quite describe it, it isn't a buzzing sound, and not quite a whine either, somewhere in-between. Is this normal, and what is it? 2 - already have rattling left air vent. Has anyone had success with Toyota stopping the noise, or anything I can do? I hate to be smacking my poor cars dashboard when she is brand new! So far, love my car! Thanks for any input. Peggy (Fernsmom)

09-09-2007, 01:58 PM	#3
qbee42 Senior Member Join Date: Mar 2006 Location: Northern Michigan Posts: 4,663 My Car: 2006 Prius Package: #7 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 4	There is also a brake accumulator pump which makes a little buzzing sound when it runs. It builds pressure for the power brakes, since the Prius cannot use engine power like normal cars. The brake accumulator pump runs about every third time you press on the brake pedal (on the average). Tom

09-09-2007, 07:47 PM	#4
leachboy Join Date: Aug 2007 Posts: 4 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Thanks to the original poster and everyone who replied. I just got a prius last friday and I was wondering about that sound as well.

09-13-2007, 03:58 PM	#6
SebMike Member Join Date: Mar 2006 Location: North Bay, CA Posts: 42 My Car: 2006 Prius Package: #6 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	On item 2, the rattling left air vent, I had a similar problem. I kept taking the silver plastic assembly on and off trying to figure out the problem, and I think I finally made it go away. Pulling that plastic assembly off is kind of tricky because it's a fairly large assembly with several retention clips that attach to the dash assembly. I've cracked a few plastic pieces here and there taking it on and off too many times, so be careful...never fun to mar a new car, right? Regardless, in my case, there were several yellow plastic clips that attach to the silver assembly. These clips kind of 'float' on the silver assembly when in place, which allows them to align and contract/expand to provide retention when inserted into the dash assembly. I found that by taking the yellow clips off and putting a few layers of tape (i.e. Scotch tape) to make the tip of the fin that the yellow clips attached to a little thicker, it cut down on the amount of 'float' for those clips. After re-inserting, my rattles went away. At least in my case, there was "too much" play between the yellow plastic clips and the fins they attach to on the vent assembly. Putting the tape in took away alot of the play and also the associated rattle. Hope that works out to be your issue and this helps... Mike

09-13-2007, 06:59 PM	#8
pmanza Fernsmom Join Date: Sep 2007 Location: Sacramento Posts: 92 My Car: 2007 Prius Package: #4 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Thanks everyone for your replies. I won't worry about the buzzing noise under the hood unless it gets real loud or consistent. The vent rattle has gone away for now, I suspect it will be one of those on again, off again things. So far, I love my car. Its funny, I just wrote up a review on Edmunds, and my list of things to improve was was longer than the list of favorite features (surprised myself there), yet I still love the car. Go figure. Most of the suggested improvements were just little niggles though. Fernsmom

09-15-2007, 04:46 PM	#10
bredekamp Senior Member Join Date: Feb 2007 Location: Somerset West, South Africa Posts: 326 My Car: 2006 Prius Package: #6 Touring Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	I was wondering about the rattle reported by many of our US friends....could this be an issue with the Left Hand Drive dashboard? Anybody from RHD countries have similar rattles?