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Hey everyone. I have a brake problem on a ‘73 f-750. Lost all brake pedal today. Master cylinder has recently been replaced. I’m wondering if the booster is bad. I can hear the booster suck air when pedal is pushed. No leaks, full of fluid. What’s the best way to diagnose a bad booster? Or has my master cylinder failed again?
Even if booster fails, you should still have brakes. You just have to really stand on them. With all that you have. Make should your seat is firmly bolted down.
Sounds to me like your master cylinder has failed again. Did you properly bleed the mc to begin with?
You may have to bleed the entire system. If the lines have enough air in them, the brakes won't engage when pedal is pressed. Air in the lines will compress while liquid can not be compressed.
Did you bleed the new master before you installed it? There may have been enough air in it to cause your issue, even though your bled the lines after install. May try that, then bleed the lines again before you buy a new master cylinder.
Based on his response, I don't think he knows the difference between bleeding brakes, and bleeding the master cylinder. They're two separate tasks. I mean no disrespect JJ. Hell I probably installed 4 in my life before I figured it out.
You should bleed the master cylinder before you install it. Watch some youtube videos. That'll explain it better than words here on the forum.
Sorry for the slow response. Yeah I bench bled the master cylinder before installation. I guess I was probably a little vague on how recently the mc was installed. It’s been about 3000 miles ago. Brakes had been working fine up until now. I just wasn’t sure on diagnosing a booster problem. Ive rebled the lines and don’t have much fluid pressure. Just a trickle. Wheel cylinders aren’t blown or anything like that. From what I’ve learned here I’d say my mc went bad.