A few moments after starting the i3 there is a hissing sound that last for 2-3 seconds - what is that?

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EVBob

Well-known member
Joined
Apr 18, 2017
Messages
154
ts not the AC compressor - that has a slightly different sound, and familiar with that sound when that comes on during charging from time to time.

The sound/hiss is much more apparent when your outside the vehicle or have the window opened while in a garage...It has always done it, so going to assume its normal. Anyone know whats going on during this sound?
 
I also notice this when your car is coming to a stop and u press on the brake pedal.

It's most apparent when you are nearing the drive-thru window with your car windows rolled down. :D

Perhaps it's the brakes making adjustments?

Either way, I find it really cool, and assume it's normal behaviour.
 
The electric vacuum pump for the power brakes? It would need to create a vacuum when the car is started and after braking.
 
ASUN said:
Either way, I find it really cool, and assume it's normal behaviour.

I think its cool as well - I would just like to know whats going on to cause the sound ;-)

I asked this on another forum, and someone chimed in their Spark EV does the same thing.... Perhaps it is the "safety box" disengaging/reengaging the relays in the battery pack?
 
My current ICE BMW makes a similar sound, but it's not very prominent because the engine mostly drowns it out.
 
After a bunch of "I Dunnos" from IConcierge/Geniuses and a few Dealerships ...I finally got the answer! - Big Thanks to Brandon and the service folks at BMW Cape Cod!

...I have an update! I finally got to speak with one of the technicians specializing in i3s. They’re telling me that the noise is the pump that moves “coolant” around the battery to keep the temperature regulated. Every time you start the car it comes on for a quick second as a test to make sure everything is working before you drive away. This is vital to the health and safety of the battery. ...
 
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