Very soft Brakes

[Big J]

1970 Dodge Challenger Rt 383 auto with air. Power Drum brakes
My Brake pedal very soft and almost to the floor. What I have done so far. New Master cylinder and bleed on bench. bleed all 4 wheels. I also check out the booster check valve. do not know what to check next.
Any help?
Big J

 

[Chryco Psycho]

Are you sure the pushrod out of the booster is adjusted correctly , if it is too short the pedal will drop close to the floor , soft sounds like there is still air in the system .

 

[Big J]

Thank you. I will look at the rod and I will bleed the brakes again. Thank you for the help.

 

[Chryco Psycho]

I assume the brakes are adjusted correctly / working properly Before swapping the master , a low pedal can be shoes not adjusted close enough to the drums also .

 

[moparleo]

Welcome. Can we get some history on your car? Is it all stock ? If not what mods have been done? The more complete info that you give us, the better recommendations we can give you now and in the future.

 

[Big J]

Brakes were not working very well. same problem soft and to the floor. I was told it was a bad master.

 

[Big J]

Welcome. Can we get some history on your car? Is it all stock ? If not what mods have been done? The more complete info that you give us, the better recommendations we can give you now and in the future.

 

[Big J]

My Challenger RT is a 383 with hooker headers. AVS2 carb auto on the floor with air.

 

[moparleo]

If you haven't done so yet, download the Service Manual for your car. The answers to most questions now and in the future can be found there.

 

[Big J]

Thank you I will do this.

 

[fasjac]

Along with the others, check the bore size of the master cylinder. Where did you get it? I’ve seen this
to cause issues in the past. Bore too large can cause these symptoms.
JMO

 

[Big J]

The master came from NAPA auto parts. Thank you.

 

[Big J]

The master came from NAPA auto parts. Thank you.

 

[moparleo]

Didn't really hear, were the brakes ever working properly since you have had the car ? If yes, when did the problem start and was anything done before the problem started ? what is the age condition of the rest of the brake system. All we know is that it is power, 4 wheel drum. Any new parts ? Brake fluid ever flushed completely from system ?

 

[Big J]

Ok when I got the car in Oct, The brakes were also almost to the floor. People had told me the master was leaking but not true. I did change it. I did bleed the brakes the pedal was ok until I start the motor and try to move the car then the pedal goes back to the floor. I find NO leaks anywhere. Could it be that I did not get all the air out of the Line?
Thanks for your help.

 

[Chryco Psycho]

Something else is wrong , are the shoes adjusted correctly ? did you check the length of the push rod in the booster ?

 

[Big J]

No I have not checked the length of the push rod. Don't really know the lenght it should be. I just assumed the brake shoes were ok.

Thank you.

 

[moparleo]

First thing is to do a complete brake system inspection. Jack stands and all. Remove all drums. Go to the brake section of your service manual. It will give you complete pictures of where everything should go and how to properly adjust everything. Just like going to the Dr. with a problem. He/she needs information to properly treat you. Fever, broken bone... Blood tests, x-rays... what ever depending on your problem. Can't just start to take pills and hope it fixes the problem. Don't start changing parts or making adjustments until you know the condition of the system and if the proper parts were replaced by previous owners.
http://www.mymopar.com/index.php?pid=109

 

[Chryco Psycho]

The pushrod needs to almost touch the piston in the back of the master cylinder so you can extend it until it does touch the back of the piston & just shorten it a 1/4 turn or so , the pushrod is 2 pieces threaded together so you can hold one end & unscrew it , if the pedal has always been low this could very well be the problem from before you owned it . you can put a felt pen mark on the tip of the pushrod to see if it is touching if you cannot feel it as you slide it into place , often it is easy to start with the pushrod too long , if it is too long the brakes will not release properly once the pedal is pushed .
to adjust the shoes you need to adjust them out with the star wheel inside the drum until they touch the drum & hold the self adjuster out of the way back the brakes off 3-4 teeth .

 

[Big J]

First thing is to do a complete brake system inspection. Jack stands and all. Remove all drums. Go to the brake section of your service manual. It will give you complete pictures of where everything should go and how to properly adjust everything. Just like going to the Dr. with a problem. He/she needs information to properly treat you. Fever, broken bone... Blood tests, x-rays... what ever depending on your problem. Can't just start to take pills and hope it fixes the problem. Don't start changing parts or making adjustments until you know the condition of the system and if the proper parts were replaced by previous owners.
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Thank you so much and you are right .