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View Full Version : New master cylinder sucking in air



brokedownboys
01-23-2024, 04:12 PM
I replaced the drum brakes and the master cylinder cuz its always been squishy. Me and GF are bleeding the system. Its building pressure, the pedal is getting harder and then suddenly she hears a big SUCK noise and the pedal collapses.

We bleed that air out, it builds more pressure until SUUUCCKKKK SLUUURRRPPP PSHHHPSHH noise and the pedal collapses again.

What is going on here? Did I buy a faulty master cylinder (Dynamic Friction from RockAuto)? The inlet unions and the brake lines are real tight. Could the piston stopper bolt or the length of the brake booster pusher be letting air in somehow?

dishman
02-25-2024, 02:09 PM
hey, where did you find your drum brakes? having trouble finding them for my baby, an '87 Auto 4wd.