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Discussion Starter · #1 ·
Hi,

I purchased 2017 Rav4 Hybrid SE model last week. If I park the car for a while and engine is off, I noticed a weird sound if I have the key next to the car or open the door. It sounds like the air compressor in refrigerator or A/C starts. It could last a few seconds and will go away. Do you have any clue what causes the sound? Thank you.
 

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RAV4 HV Limited, Prius Prime Advanced
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The vacuum pump is priming the brake booster because the car thinks you're about to go somewhere.
 

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Yeah , it happens when you open the drivers door. That's why I try use the passenger side if I'm just grabbing something and not actually going anywhere. Not that it'll hurt anything but I often forget something and no point in the extra wear of unneeded priming.
 

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Discussion Starter · #4 ·
thank you for the information. I am glad it is a normal sound. Just curious, is it a new technology for hybrid car? I never heard such sound on my conventional gasoline cars.
 

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thank you for the information. I am glad it is a normal sound. Just curious, is it a new technology for hybrid car? I never heard such sound on my conventional gasoline cars.
There's no vacuum when the ICE is off, so the booster needs the pump. Pretty much everything is different in the HV. Electric variable speed A/C compressor, etc. The 2.5 engine uses a mechanical water pump, the other HVs use electric water pumps. Electric steering, fly by wire throttle and brakes, the list goes on.
 

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Discussion Starter · #6 ·
Thank you for the information. I am a newbie in Hybrid world. With your direction, I found www(+)tomorrowstechnician(+)com/undercover-hybrid-brakes
I can't post link as new member, so please replace (+) with . if you are interested to read.

quote:
"Replacement of friction material is the same for a hybrid as it is with a conventional system, however, the ABS module will test the brake hydraulic system’s integrity by pressurizing it during key-off events – such as when the door is open or whenever the dome light is activated – and again when the key is switched on."

I guess this is what makes this noise. I hope this also help others. Thanks.
 
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