pedal travel help needed

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Rapid Robert

Rapid Robert

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73 dart disc/drum. pads are tight/shoes adjusted up/bled MC/4 corners. the pedal is almost to the floorboard tho it does stop but it is worrysome. any thoughts on where to go next? RR. EDIT forgot that I just posted this several days ago (its starting to happen!)
 
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If the pushrod is too long, the powerpiston will not return, which will then not allow the compensating port to allow fresh fluid into the system. Thus as pad material gets butned up, the pedal will sink ever lower. until one day, no brakes.

A similar situation can arise if the hydraulics on one end of the car are not working. But in this case, the pedal goes low one time, and after that, never changes, so long as the Pushrod length is good.
 
Could be m/c. When the #10 hits the pedal, the piston inside the m/c have to pass...& block...the port in the m/c that is fed by the reservoir. The greater that length of piston travel, the greater the pedal travel will be until the pedal firms up. Some m/cs have internal adjustment for this.
 
Not sure if its true but I have been told that on conversions the MC often doesn't have a residual check valve. Did the stock Mopar MCs have one? Without it there is extra travel to actuate the drum brakes. I had this issue once (non Mopar) and added an external check valve although I don't recall how much it helped....it was a long time ago.

Residual Pressure Valve placement
 
The pushrod is accessible by unbolting the m/c & moving it forward, way from the booster. If you are lucky, there will be enough movement in the attached brake lines so that the lines can be left attached to the m/cl. If this m/c & booster combo worked before, then this is will not be the problem, more likely what I described in #5.
This problem would NOT be caused by omission of the res check valve.
 
Any chance the parking brake cables are hanging or struts not allowing the rear shoes to seat on the pin when you bled them?
 
not sure, I had a shop do em, they definitely did not pull the drums. I'm thinking next will be to get a new M/C & bleed em out again. Are rebuilt M/C's adequate or should I go new? RR EDIT I did pull the LR drum & nothing looked askew
 
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FWIW, I have a rebuilt on my '69 ('74 Dart manual disc front & stock 10" X 1-3/4" rear drum). Works just fine.
Then too, a new or rebuilt MC is not going to verify correct parking brake setup.
IMO, slip the drums off and take a look. Make sure it's right mechanically then work on the hydraulics.
 
Does it stop properly? If so I would suspect that the rear shoes are having to travel too far for some reason...adjustment or mechanical problem of some sort. Its a guessing game.
 
good info. yes it does stop properly & the rear shoes are spooned up/front pads tight on the rotors, just way too much pedal travel (almost to the floor) which is worrysome as something ain't right. M/C & 4 corners have been bled.
 
Here's what I would do. With the lines in the MC loose, so the pedal can go to the floor, push the pedal to the floor while you're under the dash and hold it all the way down. Now get a black sharpie and put a reference mark on the MC pushrod even with the back of the MC bore where the pushrod enters the bore. Now turn the pedal loose and disconnect the pushrod from the pedal. Now push the pushrod buy itself into the MC as far as it will go and see if it goes in further referencing the mark you put on the pushrod earlier. If it does, you're not getting the full stroke from the pedal to the MC and the rod needs to be lengthened.
 
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