Turn the engine off,
but leave the ignition on and you'll still have power to the steering and brakes.
( monkeybananaraffle, Fri 9 Jan 2009, 14:04, 2 replies)

Not in most cars you won't
The vacuum for the servo either comes from the inlet manifold (petrol) or an engine driven vacuum pump (diesel). And the power steering is normally operated by a hydraulic pump driven by the engine.

You will have brakes and steering without the engine but you'll need to apply a hell of a lot more effort.
( K2k6 has a proper job these days, Fri 9 Jan 2009, 14:08, closed)

Yes...
K2k6 is right.

I tried it in my old S3 Land Rover once... try stopping one of those without servo assist!
(mellotron never could get the hang of Thursdays, Fri 9 Jan 2009, 14:37, closed)

So long as you're coasting
an engine going downhill like that will use next-to-no petrol anyway. So you're not saving much by turning it off when you're doing this. But you are highly likely to lose your brake servo with the engine off, which doesn't mean the brakes stop working completely but can get very exciting very quickly.

And when I say "Exciting" I mean watching the point of impact approaching rapidly while standing with both feet on the brake pedal and yodelling in anxiety.
(richardm, Fri 9 Jan 2009, 17:22, closed)