Air escaping when Braking - Alfa Romeo Forum
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Air escaping when Braking

When I press my break pedal gently about 1.5 inches I get a hissing of air escaping under the dash but when I put my foot full down it stops. What's more confusing is that it doesn,t seem to be effecting the breaking but I am due an MOT this coming week.
Will it be an MOT fail?
Has anybody else had the problem?
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Re: Air escaping when Braking

sounds like the servo is leaking, I think an mot fail
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Re: Air escaping when Braking

My 33 has always made that sound and the brakes work (well, as good as they can be on a 33). There is a foam rubber filter that surrounds the actuating rod. Look at a diagram of a servo and you'll see there is a vacuum side and an atmospheric side. A test for seeing if your servo is ok is to stop engine, press brake pedal several times and it will go hard ( the pedal). Put your foot firmly on the pedal and start engine, the pedal will depress further, but not too far. This is fine. If however the pedal goes soft after the engine has been running for a time there's a fault in the braking system. Remember the servo works by getting atmospheric pressure to provide some of the force, so the sound of moving air should not come as a surprise.

Here you go, the diagram is some way down the page.

Last edited by armoore; 26-04-07 at 18:25.
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Re: Air escaping when Braking

Quite so, I've heard such noises from servos and not found anything to worry about. If it annoys you thats a different matter but I'm sure its not the silence of the Alfa that you love it for.
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air , braking , escaping

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