Quote:
Originally Posted by sleepstar
... i'm assuming they replaced that seal as well...
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Some of those seals (square O-ring) w/ rebuilt MC's seem a bit thin to seal reliably. I have doubled-up on them or used a round O-ring from my kit.
But, w/ 24" Hg vacuum at the booster, sounds like your diaphragm inside is OK. Sometimes they get a crack that seals at different times. More commonly, a crack seals as the pedal is pushed, then you get sudden assist that throws you into the windshield.
It is normal to get atmospheric air flowing in by the pedal, since that is how the booster works. It flows thru the "air valve" as you move the pedal until the booster piston follows to close the valve. Normally, you should hear only a momentary hiss, if even that, so your air valve might be funky. In some boosters, you can buy just that part. A post here shows a booster disassembled.
I wouldn't judge by the Might-Mite test. I think most boosters slightly normally, and perhaps faster than you can hand pump, but again your air valve may not be sealing well or working perfectly.