Brake pedal, MC, pushrod issue

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supertruck

supertruck

Unretired Old Fart stock car racer
FABO Gold Member
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Location
Gloucester, Va
Vehicle is a 73 Dart 340 Sport undergoing restoration. Got rid of the power brake booster but kept the new master cylinder I'd purchased for it. Bought an adjustable pushrod from Dr. Diff and set it to the length of the original factory rod. Bled the MC, bled the brakes. Pedal is firm and stops about an inch from the floor. When I release the pedal, it does not come all the way back up. Looking under the dash, the MC piston lacks about 3/16 inch of contacting the circlip. I can pull the pedal up until the piston contacts the circlip, but the rod will continue to move another 1/4 inch or so after that if I continue to pull on the pedal. The rod cannot be pulled from the MC from under the dash so I'm guessing it's seated correctly. Any suggestions would be appreciated.
 
I had the same problem with my car. I lengthened the pushrod until the pedal returned smoothly.
 
Thanks. I tried adding about 1/4" to the length but the problem is still there - the piston does not seat against the c-clip unless I pull the peal up a bit.
 
Make sure you install the supplied washers on BOTH sides of the pivot ball. If a washer is missing between the ball and pedal arm, the body of the heim joint will bind.
 
Thanks Dr. Diff. To be honest, I don't remember getting 2 washers with my rod, only one. I'll check my washer collection today and add that second one.
 
Another question about MC's. First, when out of the car, I can push in the rod and the piston returns smoothly against the circlip, so I'm guessing something in the pedal assy is what's stopping it from returning on it's own when connected to the pedal. Also, once the piston is seated against the circlip, the rod will pull out about 1/8 of an inch more. Is this amount normal, or should the rod be tight with no extra movement? thanks guys.
 
There isn't very much holding the pushrod into the piston. At best there is a fairly tight-fitting rubber o-ring, but sometimes even those are missing, or dried-up and not doing much. So, yes, without the pedal hooked up, the pushrod can easily come completely out of the piston, but the pedal should keep it from coming out all the way once everything is installed correctly.
 
Thanks. I have one of the Dr. Diff adjustable pushrods. It is very hard to get out of the MC. I was wondering if, with this rod, there should be any play at all once the piston is seated against the circlip, with the MC out of the car.
 
Thanks AJ/formS. I noticed today that with the car up on stands and in gear, I had to put a lot of pedal effort to get the wheels to stop. I'll recheck that.
 
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