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Old 09-27-2015, 05:53 PM
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Brakes are mushy

I'm sure you all have seen this question before but it's new to me and making me crazy. This a all new brake system. Everything ......when the car is off the brakes are stiff when the car is on they become mushy but they feel like there stuck on. I have to pull the pedal up to release them. Any thoughts.

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Old 09-28-2015, 05:14 AM
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Quote:
Originally Posted by srvblues View Post
I'm sure you all have seen this question before but it's new to me and making me crazy. This a all new brake system. Everything ......when the car is off the brakes are stiff when the car is on they become mushy but they feel like there stuck on. I have to pull the pedal up to release them. Any thoughts.
When it is running can you pump them up to get a normal feel even if you have to use or hand to pull it back?

It sould like you have two issues. If there are no leaks and the Master is full, it sounds like you still have air caught in the system. You could try to gravity bleed all four at the same time or use a vacuum tool to get the air out.

Unless your Master is faulty or there is a leak or you have some bizzare proportioning valve there is air in a system that the pedal goes to the floor or is mushy.

Second, you may have a weak return spring OR your pedal lever has several leverage points for different cars and yours is in the wrong one (This less likely)

**Another thought** if it is all drums are they working correctly? Maybe the cylinder is not retracting and mushy is not really mushy but fully extended. This is less likely but still possible with disc as well and a sticky caliper.
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Old 09-28-2015, 05:55 AM
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You may not even have a brake pedal return spring that is external to the master cylinder push rod. The brakes will drag as you have found. You'll need to find a method of attaching the spring to the clevis on the pushrod so it will disallow the brake pedal from sagging and actuating the piston. On my deuce roadster, the booster and MC is under the floor. I found what I needed at the hardware store and fabricated a fix with small diameter steel rod, a relatively high tension spring and a stainless hose clamp. Hose clamp was the termination point forward on the exhaust coming from the left header. Not ideal, but it worked and is hidden. You also likely have an air bubble in the system. Also, make sure the master cylinder push rod is not disallowing circulation through the unit. Mine was not and an in-situ fix was to place two 1/16" shims between the master cylinder and booster under each bolt that held them together. You might need a thicker shim....it is trial and error. Once you get the pedal returning and a good feel to it, inspect your rotors or drums and pads for excessive wear. If you feel any pulsation in the pedal, have your rotors/drums turned.

Hope this helped. It is a frustrating issue and it took several thinkers on this one, but we got it solved.
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Old 09-28-2015, 07:32 AM
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Thanks for all the advice and I'm off today to play with it. I will keep you all informed. Thx
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Old 09-28-2015, 06:28 PM
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I have had a few boosters in 30 plus years, with an internal issue that actually would cause the pedal to apply the brakes. Pulling the pedal back with your foot would help, but at times would apply the brakes again, sometimes with different engine vacuum (operational conditions like deceleration) and sometimes for no apparent reason.
I replaced the boosters and the problem disappears.
Mushy is most likely trapped air as mentioned
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Old 09-28-2015, 07:16 PM
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Brakes

Should I install a p valve
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Old 09-29-2015, 05:34 AM
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Quote:
Originally Posted by srvblues View Post
Should I install a p valve
Not necessary unless your rear brakes are overtaking your front brakes. If you don't have residual valves installed, you need to install those. Wilwood makes excellent ones and they can be purchased at your favorite parts house. The front disc brakes require a different psi value than than the rear drum brakes. Make sure you have those valves installed in the proper direction. They will have an arrow pointing to the master cylinder etched into their bodies.
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Old 10-11-2015, 08:50 PM
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installed a porportioning valve

well its in .and its not any different mussy pedal theres a nut over the rod that looks like an adjustment rod going into the mc does that adjusts the pedal?
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Old 10-12-2015, 05:44 AM
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The nut adjusts the piston location in the master cylinder. Leave that alone for now. You still have air in at least one brake line is my guess.
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Old 10-12-2015, 06:47 AM
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if teh pedal is getting sucked down there is something wrong with the booster. Being mushy is most likely some air still trapped.
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Old 10-17-2015, 05:45 AM
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brakes and brake lines

yea the pedal is still mushy, I did notice after putting on the p valve that the tubing going to the rear brakes is a 3/16 line should it be bigger?
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