Two things. Your car is probably running a little on the rich side,
hence the significant increase in idle speed when you let in some air
into the manifold.(minor). The Fact that you are sucking in air through
the booster when the brakes are applied is completely normal. Its how
they work. When there is no brake pressure, the engine vacuum is
equalized on both sides of the spring loaded diaphragm. (Spring keeping
boosters plunger in the relaxed state). When brake pressure is applied
by the master cylinder, it moves a small valve in the booster allowing
air in to the backside of the diaphragm where it then pushes in on the
boosters plunger until that little senses equalized brake pressure.
When you then release the brakes, that same little valve then moves the
other way allowing the engines vacuum to suck all of the air out of the
diaphragm (both sides, there by equalizing the vacuum. The big spring
then pushes the plunger back out to the relaxed state again. Each time
the brakes are applied and released the engine will draw some air
through the little filter on top of the booster. It's all normal.
However....It does sound like your needs to be rebuilt. They are prone
to internal corrosion if the fluids are not changed at least once in a
while, or if the car has parked for a long time without being
driven...like 6 months +. If it has sat for a few years, then it is a
FACT that it should be rebuilt.
Rich
>----------
>From: Tom Yang[SMTP:73742.1362(at)compuserve.com]
>Sent: Thursday, August 29, 1996 9:07 PM
>To: (unknown)
>Subject: Advice on the brake booster.
>
>I'm thinking of rebuilding my brake booster on my Series V. I've got the
>Lucas/Girling rebuild kit to do it, but am not sure if I'm the man to do the
>job! I'd hate to tear it apart, put it back together, and have it not work,
>and
>have to get it done professionally anyway. What do you guys think?
>
>Here are the symptoms:
>1. When I first got the car, everything in the brake system was refurbished,
>except the booster. Very hard to get enough pressure to stop the car. As I
>drove
>the car more and more, the brakes got better (If you believe in something
>actually fixing itself).
>2. The car's idle goes up 500-700 rpm when the brakes are applied, leading me
>to
>believe there is some sort of vacuum leak. I put new hoses between the
>booster
>and intake manifold.
>3. It's not using any brake fluid.
>
>Thanks for everyone's help!
>
>Tom
>
>
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