When i unlock ny car and get in, I can hear a faint but noticable noise coming from the cabin of the car. I can hear it before and after i turn the engine on/off.(its always when the engine is off). It only sounds for a few seconds then stops. I dont know if any one has any ideas?

  • Welcome to the site. Does this happen without the key in the ignition? Or is it when you turn the key on (before you start the engine)? Please try to isolate where in the cabin (under the dash, back seat, passenger door, etc.) the sound is coming from, it will help us help you.
    – CharlieRB
    Jul 19, 2017 at 12:52

3 Answers 3


I suspect you are hearing the lift pump priming / purging the fuel lines.


On my car (Jaguar x type) there is a very small fan close to the instruments that samples the cabin air for the heater / AC, what you describe sounds just like mine.

However, they are normally almost inaudible - perhaps it needs a clean but be very careful they are delicate. Don't use a garage airline :) but one of the electronic air puffers may work.


On my different car (2016 Toyota RAV4 hybrid), I also hear a similar buzzing noise after unlocking the door. The noise is almost surely some kind of electric motor, but the question is, where?

In the case of my car, I assume it is the brake booster electric pump. So it is not coming from the cabin of the car; it occurs under the hood. The reason an electric brake booster pump is needed is that the car is a hybrid, and thus, does not always run the engine when in motion, but brakes need to be ready to be operated always.

Is your car perhaps a diesel? If so, it doesn't have manifold vacuum and a pump is needed for the brake booster. So, it could be brake booster vacuum pump you're hearing.

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