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77BBGMC · 08-11-2011, 10:28 PM

I installed a new master cylinder last night, did the bench bleed on the MC and once installed bled the breaks. It was late when I finished and I could tell I still had some air in the lines. I drove it around the neighborhood and when I got home double checked to make sure no leaks on the MC, all seemed good. Tonight I re-bled the brakes and was struggling to get the air out, I used a hand held vacuum unit and did it the traditional way. I started it up to move it and my brake pedal went to the floor and the brake light stayed on. After that I couldn’t build any pressure in the lines. I’ve pumped the brakes countless times with no luck. Would it be possible that something happened to my brake booster while I was bleeding the brakes? I noticed something odd, the front of the booster expands (not a lot) when the brake pedal is pushed in. Any thoughts?

08-11-2011, 10:28 PM	#15
77BBGMC Registered User Join Date: May 2009 Location: Kansas Posts: 357	Re: Master cylinder lid leaks, why? I installed a new master cylinder last night, did the bench bleed on the MC and once installed bled the breaks. It was late when I finished and I could tell I still had some air in the lines. I drove it around the neighborhood and when I got home double checked to make sure no leaks on the MC, all seemed good. Tonight I re-bled the brakes and was struggling to get the air out, I used a hand held vacuum unit and did it the traditional way. I started it up to move it and my brake pedal went to the floor and the brake light stayed on. After that I couldn’t build any pressure in the lines. I’ve pumped the brakes countless times with no luck. Would it be possible that something happened to my brake booster while I was bleeding the brakes? I noticed something odd, the front of the booster expands (not a lot) when the brake pedal is pushed in. Any thoughts?