The push rod is part of the power booster or if you have manual master the rod is held to the master and you really need to yank it out when changing a manual master.

Also the rod from booster to master is part of the booster and as posted earlier that rod can be adjusted and has been checked many times.
The time is it has to come all the way back or the piston of the master will not release pressure or let fluid back in the bore for the next push.
I have gone tighter and looser with no change in the pedal or braking if I took a test drive.
Dave ----

 

My brake pedal travels maybe an inch. Your long travel is not correct. I'm out of ideas for you on that one. You get no braking for the first 3" of pedal travel? I don't see how the PDV could be responsible for that amount of travel. When was the last time you adjusted the rear shoes?

 

Same here. Doesn't take much travel for max braking power in my F250.

How about this? Disconnect and plug the two lines at the MC. Have the plugs ready and do it quickly and you won't lose much fluid. See how the pedal behaves now. If nice and firm with minimal travel, the problem is downstream. If travel is still excessive, the problem is with the MC, booster, or the linkage to it.

 

I have one inch of travel too. I just drove her today and made a point of noticing.

Years back, the trusted mechanic said, the soccer mom's didn't like the hard brake pedals, in their new SUV's, so the MFG's began to disgne in softer brake systems.

Back about 2010 or so when he replaced the Booster because I had to pull the pedal back up after using the brakes, he told me he had to get a few boosters before he found one he was happy with. He went on the say, Iif I wanted somethng better to come back.

 

It was not that long ago when I had to replace the rear brake spring and found the cracked linings so it get new shoes.
I am pretty sure they are not out of adjustment as the rears are the only thing working. If they were out of adjustment the pedal would be low but the fronts would lock up as they dont go out of adjustment

Now dont go getting a big head but I do like this ideal and I think I got the fittings to do this test.
Thing is it will be a few weeks before I can run it. Think I will order that valve and being the system is open replace it then.

I dont think or see how the booster could make the pedal low and the front brakes not work.

Going to try what Karl posted when I can and see what happens and report back but it will be a few weeks before I can do this.
Dave ----

 

If you have the wrong master cylinder for the system you have now, your pedal travel will be messed up. If the bore diameter of the master is too small, you will have lots of travel. If the master cylinder bore is too large, you will not have much travel but the pedal effort is increased.

I did not read through the whole thread, but from what I have been reading you have been mixing and matching brake components. Just make sure it's right for the system you have.

 

Too late. I was in the kitchen when I read your post. Now my head has swelled and I’m stuck here for a while. Maybe my wife is nearby and can remind me of my shortcomings.

Dang, I’ve got to pee really bad. Knew I shouldn’t have chugged all that Mountain Dew. My wife will be really mad at me if she catches me peeing in the kitchen sink again…

 

The PDV won't allow front braking until the rear shoes have made contact with the drum. And you have to go 3 inches of pedal to get rear only braking. I think the other Dave is on to your issue and that is the master diameter. I'd check that and make double dog sure you have the right one.

 

Another thought: When troubleshooting, don't be misled by the effects of the power brakes.

The booster will have a check valve to hold vacuum. This allows two or three boosted applications even if the engine stopped. This is a safety feature so the pedal effort doesn't drastically increase if the engine stalls.

To bleed off this reserve, shut off the engine and press the brake pedal three or four times. Now you'll be in unboosted mode for all subsequent troubleshooting, until the engine is started again. You don't want a mix of boosted and unboosted while comparing pedal action.

 

Before I did this swap I checked and will again that both the power & non-power masters had the same 1 inch dia. bore but neither listed stroke.
The rear wheel cylinders had the same part numbers between the 2 systems.

In looking about the calipers they both had the same dia. pistons but the part numbers were different because how they bolt to the knuckle.
And I am sure the only reason for that is because of the kingpin size and wheel bolt pattern differences between the to systems.

I just ordered the PDV and as said by Karl I will test the master at that time.
Dave ----