981 whoosh noise when braking

[Bolts100]

Hi
Just changed my 987.2 for a 981 and noticed today there is a whoosh noise when I brake. My question is, is this normal or signs of a failed servo?

https://youtu.be/J8D4HoKW53I

Thanks guys

[Green1man]

What are you doing there? Pressing the brake while car is stationary with engine off?

It’s not normal to have this sound when the car is running, but with engine off I’m not sure.

[Bolts100]

Hi
Engine is running.

I'm pushing down on the brake peddle. If I turn the engine off then pump the peddle a few times the noise stops and the brake is stiff

[SV_WDC]

No idea if this is related but could be worth checking when the break fluid was last replaced? Maybe there is a leak in the system also.

[Green1man]

Yeh, sounds like maybe some air in the system or something, I’d start by getting the system bled and the fluid changed and see if that solves it.

[anonymous-user]

Pretty much all modern cars have a brake booster system which is operated by vacuum from the engine manifold. That's why if you roll down hill using the brakes, with the ignition off, after a few pedal applications the remaining vacuum will be used up and you'll find you need a huge push on the pedal to stop the car. You are then braking without boost.

So, when you brake under normal conditions there has to be some air moving about - that's how the booster works - with air pressure on a diaphragm. When that air is moving about it can produce a quiet whooshing sound.

Very often if your car has been standing for a while, then you jump in and start the engine with one foot on the brake pedal you will feel the pedal move as the boost system becomes energised by vacuum from the running engine.