how to test brake booster

[azruss]

Bled my brakes this morning. with the motor off, the pedal is high and tight. when i start the engine and drive the car. i dont get any braking until the pedal is half way to the floor and required more foot pressure than i remember. I cannot lock up the brakes. this tells me the booster is either non functional or the rod between the booster and the MC is out of adjustment. How can a test the system to see if the booster if functional.

[Tobi]

Turn the motor off and pump the brakes several times. Than keep the pedal down and turn on the motor. The pedal goes further down...the booster works fine.
When you bleed the brakes the old fashioned way there is a risk of hurting the membrane when you pump the pedal down to far.

[azruss]

Ok. when i measure the pedal drop with the motor off, the pedal drops 1 1/2" from the top resting position to where pressure significantly stops travel. when i turn on the motor, the pedal drops another 1". This means that when the motor is on, the pedal depresses 2 1/2" before i get braking. I recall my old spiders dropping when the motor is on, but seems like it wasnt this much. would love to hear what others are getting.

[fiatfactory]

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[htchevyii]

I would think that if you hooked a vacuum pump up to the vacuum port and it holds vacuum then its good. Boosters are actually really simple, as long as the diaphram is good it's OK.