Hissing brake servo...

[Fastra]

2009 Astra H 1.8 - 62k miles.

Just noticed a 'hissing' noise that stops when I press the brake pedal.
Had a look around and I think it's coming from inside the cabin, from the brake servo - just behind the pedal.

There's no change in brake performance, but is it safe to drive?

Obviously I will get it a garage to look at it but in the meantime just want to be sure it's safe.

[stevieturbo]

Sounds like an air leak....presumably a high or abnormal idle too ?

[Fastra]

idle's fine - solid 750/800.

it seems to be coming from the cylinder behind the brake pedal - the collapsible bit.

[GreenV8S]

The most likely cause is that you have a vacuum leak. Since you have no idea what is causing the leak we have to assume it could get worse without warning and might potentially lead to total servo failure. If you've ever tried to drive a servo assisted car without the servo working you will appreciate how dangerous this is. If that was me I'd treat this as a breakdown and not plan to drive it until a mechanic has diagnosed the problem and told me it is safe to drive.