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Rio24

No brake pedal when car running

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Hello Guys,  72 240Z.

I'm almost ready to drive the car I bought last year, but I can't get a brake pedal when engine running.  It feels pretty firm with engine off.   I have replaced everything except booster and lines.   I have bleed multiple times, so I'm sure of no air in system.  In my experience when a booster is bad the pedal will be harder when car started.   Any idea?

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1 hour ago, Rio24 said:

 

Edited by Zed Head

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That's exactly what is means.   Doesn't really drop to the floor on its own.  Just no resistance when pressing down.  Pedal does return to the top.   I bought the car with a seized engine and got that going .   Next was the brake system need attention.   I replaced calipers pads rotors and drums ,wheel cylinders ,shoes and hardware.  Not sure what else you need.   Thanks for your time zed head

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OK  Zed head.   Just giving you details.  Master has been replaced

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Good luck.

 

Edited by Zed Head

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I don't understand your point?   I'm here for help Zed.   You wanted details, I gave them to you.   What about the bleed screws?   They are all working properly.  I bled the system a few times.  Pressure, vacuum and manually bled just today.   

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I'm sorry but I thought the title of my post explains my symptom Zed head.    Everything has been replaced except lines and booster.   

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Back to the future...

Edited by Zed Head

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Is that what you call helping?  More like wasting time.  Glad I could help with your boredom sir.  

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Although, the part about boredom is on-point.  So, thank you for that.

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Have you tried going through the troubleshooting section of the FSM?

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Hi Steve   I have. And it all leads to air in system.   I've bled it multiple times and different techniques.  Stumped! 

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Check the calipers. Make sure the bleed screws are at the top of the caliper. Sometimes people install them on the wrong side, and the bleed screws are down. That traps air to the point that it is difficult to impossible to purge.

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Symptom of reaction disc falling out when changing master cylinder. Fairly common. Happened to me.

Pull master and push rod. Fish out rubber disc and glue on to end of rod and reinstall rod and master.

reactiondisc.jpg

  • Like 2

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Thanks guys!   I will check for the reaction disk tomorrow.  

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Hey guys,   the reaction disk was in place.   I tested the booster and check valve and bench bled the MC while I had it out.  Pressure bled system and still same thing.  I'm thinking I'm going to gravity bleed at every fitting of system this weekend.  It has to be air in system!  Right!?   I Really appreciate your suggestions,  thanks 

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Reaction disk aside, are you sure you don’t have a hole in the booster diaphragm? Do you have any engine speed increase when you step on the pedal with it running?

 

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