Brakes not holding pressure?!?!
#1
Oh wonderful experienced people please share your wisdom with me Thumbup. Alright...I have replaced the front (rotors, calipers, and pads), back (wheel cylinders and hardware), and the power booster/master cylinder. I bled the master cylinder and all the brakes last night and had correct brake pressure for the first time ever! (car was not running when I did all that) I woke up this morning and had no pressure again what so ever Angry. Besides that I also had spark issues with starting the car (found out that it was the wire leading to the coil...it looks ugly covered with so much electrical tape-going to replace the wire). Anyways...there is no leak of brake fluid anywhere. The fluid levels in the master cylinder are the same. I am thinking that it might be a vacuum leak from the power booster to the intake? please help me out :)
Current Car:
1973 Mach 1 'Q' code Automatic= "gg" Glow Gold for short SCo_hmmthink
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#2
alright did a lot of redoing on most of my brake system in general (also...replaced vacuum line to intake and redid back brake adjustment). I have a semi different issue now. When car is off I have full brake pressure after maybe one to two pumps of the brake pedal. When I turn the car on...the pedal almost goes completely limp. I have to pump a good 5-10 times to get barely any pressure at all. If I stop pumping and give it like a 5 second break the pedal is almost completely limp again. I am lost but I am just going to google it a lot more. Hopefully someone knows that little trick of the trade that I have no clue about. Thank you all!
Current Car:
1973 Mach 1 'Q' code Automatic= "gg" Glow Gold for short SCo_hmmthink
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#3
HAVE YOU TRIED THE VACUUM CHECK VALVE ON THE BRAKE BOOSTER? FORD PART NUMBER SHOULD BE D0AZ 2365 A. WHICH IS STILL AVAILABLE FROM FORD. Biggrin
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#4
A new check valve came with the refurbished booster. I am assuming it is just fine. One of my friends is heading over and I am going to bleed and bleed and bleed some more on my MC and brake lines. So I know without a doubt there is no air in the system. Wink
Current Car:
1973 Mach 1 'Q' code Automatic= "gg" Glow Gold for short SCo_hmmthink
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#5
I would have to agree with your decision to bleed some more. Also try cross bleeding the system. If there is no fluid loss then it is indeed an odd issue if it is not just air in a line.

The proportioning valve is what comes to mind if it is not just a trapped air issue. That is about the only thing that will allow the effect you speak of.

Let us know what you find.
[Image: Arizona_flag_32w.gif]
Southern Arizona
Current Mustangs:
1973 Mach 1

1971 Mustang Grande
1965 Mustang
[Image: stevenharris.jpg]
http://www.mexicomissionariesofcbt.blogspot.com/
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#6
Going to take the time and bleed each line with a half-full small bottle of break fluid. Hopefully after this any and all air will be gone. Thank you all :)
Current Car:
1973 Mach 1 'Q' code Automatic= "gg" Glow Gold for short SCo_hmmthink
Reply

#7
how are you bleeding the system? pumping the lines up and bleeding with someone on the pedal or using a hand held vaccuum setup? D id you benchbleed the master before putting on?
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