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Hi I live in Los Angeles and was on a trip in the Owens Valley and in the morning at low temps around 40 to 45 when I start the car I gat a WHIRRING noise from the booster motor (I believe) and two loud click noises.
I also hear a squeck noise from the front or rear brake every time I apply the brake..

Now when I get back to LA and warmer temps ALL noises go away!

Anyone else hear this or have this noises??

PS 2005 with 10K ...
 

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It's not just the cold, but the dew point. All brakes get a thin coating of rust overnight when the temperature hits the dew point. Most cars scrape it off with the first brake application, but the seldom-used Prius brakes take longer. The pump noise is probably normal.
 

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The "whirring" noise is mostly likely the sound I routinely hear... in Minnesota, where we have a much different definition of "cold".

If you have a squeak, it is the brakes on your particular vehicle.

As for clicks when driving a HSD... nope, none, nada. The only one I hear is when the seats are down. During startup, the big electric relay next to the battery-pack will click once. You could hear the electric relay under the hood of the Classic click while slowing down during the winter only. But not during the summer and not in a HSD.
 

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The whirring from the power steering motor/gearing is normal. It will be more noticable when you have the HVAC off or barely on and without AC. I heard it myself when I was parking in the lot here at work, as I had the AC compressor off, fan at low, so there was little fan noise. The only sound that could have drowned it out was the radio.
 

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KTPhil said:
It's not just the cold, but the dew point. All brakes get a thin coating of rust overnight when the temperature hits the dew point. Most cars scrape it off with the first brake application, but the seldom-used Prius brakes take longer. The pump noise is probably normal.
I've had the brake noise occur each time I've traveled up to Lake Tahoe. It continues while at altitude and also initially after returning to low altitude. It doesn't sound like rust on the rotor or drum and it continues on repeated stops so I don't believe that's what is causing it. It continues when I return to sea level (Menlo Park) but after parking overnight, it goes away. It has happened on at least six trips. My wife, now comments, "There's the chirp again". I posted several months ago on Priuschat and got only a few responses. Still looking for other suggestions. To me it sounds a little like a squeek you might get from a shaft sliding through a dry seal but it is very short duration, when you first depress the pedal, and doesn't continue during sustained braking. It also seems to be little less persistent during the summer months so it may be a combination of low temperature and altitude.
 

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Could be the wheel cylinder seals, or even the master cylinder seals. As long as they aren't leaking, shouldn't be a problem.

Guess that would be something for dealers to inspect every 15K-30K miles.
 

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Our 2002 Prius has the nickname of 'Squeaky' for this reason. We had it to Toyota twice about the issue, but they were unable to find a malfunction. I was thinking that it might be a thin coat of condensation on one of the clutches in the planetary gear transmission rubbing off when the clutch engages (about 1000 feet down the road after startup on a cold morning), but we are not really interested in dissassembling the engine/transmission to find out. Things to think about: Is the car stored outside? Is there a coating of frost/ice on the windshield?

-still happy as a clam with 'Squeaky'.
 

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"clutches in the planetary gear transmission"

There are no clutches in the HSD system.
 

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They are all "free-wheeling". Sun controlled by a motor generator, planet carrier by the gas engine (planets just spin), and ring controlled by the wheels and a motor generator.

The motor generator connected to the sun has the best leverage, so orchestrates the rest.
 
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