Brake issue

[moparspares]

73 Duster with Front Discs and 10.5 drum rear. Had an issue with pedal not returning and assumed it may have been booster. Replaced booster and while at it replaced MC. I drove it and hit the brakes and it now wants to throw me through the windshield - very touchy indeed and pedal still not returning. Everything in the system is new except calipers. I might add I only bled them with an Airboy which is feckin useless. I will find someone to give me a hand to bled as I still think it has some air in system. Any ideas?

 

[rustycowll69]

10.5? It's been decades, but aren't they like 9" , 10", 11" nominal dia.?
If they are too sensitive, it doesn't sound like air in the system. Usually air makes pedal soft and spongy.

 

[moparspares]

10.5? It's been decades, but aren't they like 9" , 10", 11" nominal dia.?
If they are too sensitive, it doesn't sound like air in the system. Usually air makes pedal soft and spongy.

I meant to say 10 x 2.5 but my brain and fingers wern't in sync

 

[CL3406]

I meant to say 10 x 2.5 but my brain and fingers wern't in sync

Everything in your brake system is designed to return, from the drums, calipers, booster & master. It really is just a process of elimination..Jack up the car all 4 wheels or put it on a lift. At rest see if the car has brakes applied, if so unbolt the master from the booster and slide it forward. See if there is a change back to normal disc/drum drag?? If yes look at adjustment in the booster or at the brake pedal. If no change and the brakes are still applied look at the master cyl? Maybe the compensating ports are covered up? Maybe the return spring is broken in the master?? Lots of options, like I say just a process of elimination. Here is a schematic of a master just so you can see how they are assembled. As you can see they are designed to return and open up the compensating ports. The design of the caliper piston o rings pull the pistons back to rest, the brake shoes use the return springs, booster has a large spring that works against vacuum(most boosters). The only other part would be a metering block or proportioning valve. Possible an issue there as well but not very common to create issues. One step at a time & you will figure it out I'm sure. The I hope this helps? Good luck!

 

[rustycowll69]

I've read, but not experienced myself, that there can be a danger of damaging m/cyl by pushing the pedal all the way to the floor while bleeding. "They" recommend putting a 2x4 wood block below brake pedal to prevent this over travel damage.
Did you bench bleed the m/cylinder before installation?