magicnote
Posts: 12
Joined: Sun Feb 05, 2012 10:04 am
Location: Seattle

Unusual sound from underside of car

Sun Feb 05, 2012 2:27 pm

Hello i Owners,

My wife and I just took delivery of our i last week and we love the car. I have been hearing a noise that sounds a little off. When I put the car in drive after reversing first, there is dull clanking sound that I hear after few seconds of moving forward. Is anyone else hearing this? I only hear it once and then not again for the rest of that trip.

jjlink
Site Moderator
Posts: 401
Joined: Sun Sep 11, 2011 8:26 am
Location: San Francisco Bay Area, CA

Re: Unusual sound from underside of car

Sun Feb 05, 2012 5:13 pm

Yes, I also hear a noise like something motorized is moving/adjusting under the car when just starting to drive after backing up. I don't what its, but I am assuming its normal. Anyone know what is the source of the sound?
John - 2012 Silver i-MiEV SE model, Jan 19th, 2012 w/OpenEvse, caniOn,& OVMS.

oahumiev
Posts: 57
Joined: Thu Jan 26, 2012 12:32 am
Location: Oahu, Hawaii

Re: Unusual sound from underside of car

Sun Feb 05, 2012 6:02 pm

At first I was also wondering what this was but after 2 months of driving it and hearing this sound after each startup, I did some research and it seems like its the air brakes, there's some info in the owner's manual regarding hearing possible noise when first driving, the sound should not be heard after the initial acceleration.

JoeS
Site Moderator
Posts: 3937
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

Re: Unusual sound from underside of car

Sun Feb 05, 2012 9:34 pm

oahumiev, perhaps what you're referring to is the vacuum pump for the power brake booster? Most electric vacuum pumps I'm familiar with are awfully noisy, so I'm impressed if they've almost fully muted the sound and I don't recall hearing it at all on my test drive. I would expect to hear it for a few seconds at startup. In any event, it should be intermittent and also occur for a few seconds after significant braking (and not simply slowing down which uses regen which is what occurs when the brake pedal is first depressed).
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

oahumiev
Posts: 57
Joined: Thu Jan 26, 2012 12:32 am
Location: Oahu, Hawaii

Re: Unusual sound from underside of car

Mon Feb 06, 2012 12:22 am

"oahumiev, perhaps what you're referring to is the vacuum pump for the power brake booster?"

Yes, i was trying to refer to the vacuum pump which assists in the braking process, thanks for the proper name. It's not a loud noise but definitely audible thud. Was worried initially since it sounded like I ran over something but now just used to hearing it after first acceleration, don't hear it at all following that.

Wee John
Posts: 134
Joined: Thu Jan 12, 2012 6:15 am
Location: SF East Bay

Re: Unusual sound from underside of car

Mon Feb 06, 2012 1:34 pm

The noise you are hearing is the self test for the antilock braking system, it does this test the first time you start the car and start moving. If you want to hear the vacuum pump for the brakes you can sit in Park and press the brake pedal three or four times.

magicnote
Posts: 12
Joined: Sun Feb 05, 2012 10:04 am
Location: Seattle

Re: Unusual sound from underside of car

Wed Feb 08, 2012 2:56 pm

Thanks for all the replies! I'm glad other people are hearing the same thing and that is seems to be an expected sound.

iMiEV808
Posts: 40
Joined: Sat Feb 25, 2012 2:55 pm

Re: Unusual sound from underside of car

Tue Feb 28, 2012 2:46 am

There are several noises that can be heard while driving an iMiEV. The clunk on 1st drive off after a key start is the ABS self check. A buzz sound from the right rear of the vehicle can be heard every time you press the brake pedal. It is the vacuum pump that builds vacuum for the brake booster. If you pump the brake pedal enough times and deplete the vacuum before the pump can catch up, you'll hear a warning tone inside the vehicle. The noise that sounds like a tram is the AVAS. To hear it with the car standing still, apply the parking brake, put the vehicle into D range and let off the brake pedal.

alohart
Posts: 377
Joined: Wed Apr 25, 2012 10:15 am
Location: Honolulu, HI, and Uppsala, Sweden

Re: Unusual sound from underside of car

Tue Jan 15, 2013 12:56 pm

Wee John wrote:The noise you are hearing is the self test for the antilock braking system, it does this test the first time you start the car and start moving.

Mitsubishi must be receiving enough questions about this noise that they've instructed their salespeople to explain it. Or maybe this explanation was offered by my salesperson on his own volition. I have another car with an ABS system, but I've never heard it perform a similar self-test. Maybe its engine drowns out the sound. But with my i-MiEV, the ABS self-test clunk is very noticeable, so I'm glad that I was told to expect it and that it is totally normal.
Aloha,
Art
Honolulu: 2014 BMW i3 BEV (formerly 2012 i-MiEV SE)
Uppsala, Sweden: 2000 Honda Insight

iMiEVNZ7
Posts: 122
Joined: Mon Feb 13, 2012 7:45 pm

Re: Unusual sound from underside of car

Tue Jan 15, 2013 3:53 pm

Yes, The Holden Adventra V8 also does this on startup, and if one has the foot on the brake pedal, you can feel it firm to start with, then on key turn and engine starting, feel the brake go down a bit like the pressure is slightly released, the a push upwards from the system felt through the brake pedal is noticeable. like someone giving the pedal a tiny kick.

We don't notice it if starting without foot on the brake as sound of engine starting is higher than noise of ABS CHeck.

For the iMiEV , yes in NZ it is the same as others have mentioned, noise on start off, then only vacuum pump sometimes.

I am thinking of adding a V8 sound to make the car more quiet to the ears to mask the road noise.

Return to “General Technical Discussions”