gerry@probe.att.com (Gerry) writes:
> My question is how does one know if the booster is going south ? If I stomp
> hard on the brakes, I do not get a fluid leak, so I know that it is okay
> internally, but I seem to remember that with the engine off, if you press
> the brake pedal and start the engine, the pedal will drop slightly and then
> rise again as the booster comes into play. Is this correct ?
The first part sounds familiar; generally speaking, when you start the engine
with your foot on a power brake system, the pedal will drop slightly as the
vacuum assist comes in and amplifies your foot pressure. I have not seen any
system where the pedal will then "rise again" by itself (if you mean that you
kept your foot on the pedal, but it pushed back up again after a few seconds).
Perhaps you are expending all the boost at once, and the resistance in the
brake system is managing to shove back at you. Just a wild guess.
> Also if I remove the vacuum line from the inlet manifold and suck on it,
> should I hear/feel something ?
Dunno. There is customarily a check valve in the line to keep vacuum in the
booster when vacuum falls in the intake manifold, so you would have to over-
come that valve. It might make a "click" or something if you suck on the hose
hard enough. I think it would be more revealing to pull the hose up at the
booster end, and see if it's drawing vacuum properly.
> The other area I am going to inspect is the caliper pistons. I am going to
> remove the pads and press on the brake pedal to see if the the pistons are
> moving all the way out...
Hey, be careful with that. If you have ANY residual vacuum in the booster,
it can blow the pistons clean out of the calipers if there is no rotor to
press against. If you suspect the calipers, I suggest you remove them and
bench test with a gentle source of pressure in the line, such as a small
air pump.
Andrew C. Green
Datalogics, Inc. Internet: acg@dlogics.com
441 W. Huron UUCP: ..!uunet!dlogics!acg
Chicago, IL 60610 FAX: (312) 266-4473
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