Mechanical purr?

kman42 · 04-05-2007, 11:56 AM

I frequently hear a mechanical purr in my new 2007. It lasts only a second or two and I think it comes from the drivers side front, but localizing car noises is difficult for me. It seems to mainly occur after starting driving from a stop or slowing down at low speeds. Something to do with the ICE coming on/off? Regen braking?

I've only had the car two weeks, so I'm not sure what is normal. We have about 350 miles on it and are averaging 45mpg, so I don't think there is anything wrong.

kman

iaowings · 04-05-2007, 11:59 AM

It is the brake system. I think there is a pump on the driver’s side. It is a normal noise so don’t worry. I am sure someone here can expound on exactly what part and how it works and all that but all I know is it is part of the brake system and is normal.

David Beale · 04-05-2007, 04:21 PM

One of the cool things about this hybrid system is the engine can be shut off at any time, without the driver actually commanding it (directly).
Because of this, any system that "normal" cars use that rely on the engine running had to be run off a battery, either the HV one or the 12V one.

Sooo, there is an electrically powered hydraulic accumulator pump for the brakes, instead of a vacuum booster.
There is an electric motor for the AC.
There are electric heaters for the interior (boost only).
And others.
They all make noises at unusual times (compared to "normal" cars), mostly rather quiet ones, but worrying to newbies.

I believe the saying repeated often by dealers and enthusiasts here is "Don't worry, be happy. It's normal."

04-05-2007, 04:21 PM	#3
David Beale Senior Member Join Date: Jul 2006 Location: Edmonton Alberta Posts: 1,330 My Car: 2007 Prius Package: B Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	One of the cool things about this hybrid system is the engine can be shut off at any time, without the driver actually commanding it (directly). Because of this, any system that "normal" cars use that rely on the engine running had to be run off a battery, either the HV one or the 12V one. Sooo, there is an electrically powered hydraulic accumulator pump for the brakes, instead of a vacuum booster. There is an electric motor for the AC. There are electric heaters for the interior (boost only). And others. They all make noises at unusual times (compared to "normal" cars), mostly rather quiet ones, but worrying to newbies. I believe the saying repeated often by dealers and enthusiasts here is "Don't worry, be happy. It's normal." __________________ Edmonton Alberta "Pearl" is a 2007 Driftwood Pearl Prius.

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04-05-2007, 11:56 AM	#1
kman42 Join Date: Mar 2007 Posts: 5 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	I frequently hear a mechanical purr in my new 2007. It lasts only a second or two and I think it comes from the drivers side front, but localizing car noises is difficult for me. It seems to mainly occur after starting driving from a stop or slowing down at low speeds. Something to do with the ICE coming on/off? Regen braking? I've only had the car two weeks, so I'm not sure what is normal. We have about 350 miles on it and are averaging 45mpg, so I don't think there is anything wrong. kman

04-05-2007, 11:59 AM	#2
iaowings Join Date: May 2006 Posts: 450 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	It is the brake system. I think there is a pump on the driver’s side. It is a normal noise so don’t worry. I am sure someone here can expound on exactly what part and how it works and all that but all I know is it is part of the brake system and is normal.