wouldn't a stuck check valve give a very hard pedal ?
or are we contemplating the fact that if the check valve is open, then it would leak the air out of the booster giving a very low pedal in return ?
I did not notice a check valve at the point where the vacuum pipe connects to the booster. do some boosters have internal check valves ?
pumping the pedal gives a high/hard pedal. could that be a symptom of faulty check valve or booster ?

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