I have a 71 F250 with drum/drum front & back. Factory power brakes, booster & master cylinder. If I push down on the peddle the brakes make stopping contact with the peddle foot pad about 1" from the floor. It used to make brake contact at 2.5 - 3" from the floor.

When I hold foot pressure on the peddle it does not go down any more like I have a master cylinder that has a internal leak. Pumping the peddle 3-4 times does not build any more free peddle. The power booster is working as it should. No heavy foot pressure needed.

Anyone had this same problem?

 

How many notches does it take to apply the parking brake?
I’m just curious if your back brakes have gone so far out of adjustment that it takes a long time for the shoes to travel to the drum linings.
If all four brakes are in this condition a low pedal would be the result.
It’s not the only thing that can create that, but it is one possibility.

Have you done anything to the brake system recently? Replaced any parts or made any adjustments?
And speaking of which… How long has it been since you adjusted the brakes?

I guess another question might be did it come on suddenly, or gradually?

And have you checked if it is low on fluid?
Had to ask!😁😉

 

One Ton BC -
1. Not sure on the parking brake notches, will check.
2. No work on brake system in last 6 months.
3. Brakes set with star unit 1 month ago.
4. Fluid level checked, was full.
5. Came on slowly, little less peddle over a 3 month period.
6. Has stayed with 1" peddle to floor clearance for last 4-5 months.

Would power bleeding the system be a good idea?
After bleeding should brakes be adjusted?

 

Seems like that could be a small leak allowing air into the system
In theory you should be able to spot some seepage from somewhere or another, but I've heard of air getting in without letting liquid out.

Could still be a leak I suppose. Consistent perhaps with a leak in one circuit only (front OR rear) where the other is holding pressure.
Can you tell if one set of brakes is holding better than the other? Brake power feels normal it sounds like, but can you lock up the rears when driving? Could you ever?

When was the last time it was bled? I don't imagine it's a bad thing to do, other than wasting fluid if it's not an air issue.
But you really won't know for sure until you do bleed it.

Seems like if it's air in the system then bleeding (any method) would cure the low pedal temporarily. But then you might experience the same slow degradation over time.
That would seem to indicate a very small leak. Was the fluid low at all in either reservoir that might give a clue as to where something is amiss?

I've always done the mechanical before the hydraulic, but I don't see anything horribly wrong with doing it either way. In fact it often does get done in either order based on what is being done to the system.
But I would re-check the recent adjustments and if any is needed, test the pedal first. Then bleed it.

If it does go away after bleeding. Go over the entire system inch by inch to see if anything is loose or rusting through.
And even though the booster seems to be doing it's job, it does not take much effort to remove the two nuts and pull the master away from the booster just to give it a quick visual inspection behind there. If you see fluid, you likely found your issue.

Good luck.

Paul

 

1 ton BC - Paul, thanks for the reply and a few things to check. Will try to check a few item's next week. Don't feel like the brake system would lock up the rear brakes ever. Might pull the MC from the booster & check for fluid first, then fill & bleed the system a couple of times then adjust the shoes again. When you remove the two MC bolts does the MC pull off with no connections? Never had mine off.

 

Correct.
After you remove the two fasteners (usually nuts on studs) the only thing attached to the master cylinder after that are the two hard brake lines.
However there is usually enough flexibility in their make up that you can pull the master cylinder forward at least far enough to look inside without doing any over flexing of the lines.
But look at yours specifically just in case the lines have been changed and are more rigid.
In other words, if it doesn’t want to come out very far, don’t pull too hard.😉😁

 

Adjust the drum brakes before bleeding.
Heck you may find after adjusting the pedal is fine.

I did have a year old master that would not pump up even after power bleeding. It was just a bad master and replaced it with new not rebuilt.
Dave ----

 

FS2 - Ya I will adjust all 4 drums first. I have not done this myself for 20+ years. I used to tighten up the adjuster until the wheel would not spin, then back off the adjuster 3-4 notches. Is this the correct way to do them? Also do you rotate the notches up or down to expand the shoes in the drums?

I do not trust rebuilt master or wheel cylinders. New ones are best. Even then you might get a bad one now & then.

 

A question on adjusting brake shoes in drum brakes? Can you jack the tire up a few inches off the ground, spin it and tighten the star adjuster until you can not turn the wheel, then turn the star adjuster the other way a few notches until you can turn the wheel again. There should be no brake shoe to drum drag.

Is this the correct way to adjust the shoes or is there a better way? What is the normal amount of notches to back off the star adjuster? Thanks for any comments.

 

I usually back the adjuster wheel 10 clicks from locked.

 

When was the last time brake linings were looked at? I'd look before bleeding. Also, when rotated, like jacked up and rotated, you should hear a light scuffing noise. Brakes do not self adjust except when backing up and hitting the brakes .... and then only a tooth or so at a time ... if equiped with self adjusters. Backing out of a driveway on a hilly street keeps them up pretty good.

 

Thanks guys for all the comments. Front drums removed & brake shoes checked OK about 2500 miles ago. I only put 3500-5500 miles a year on my rig. Rear drums a much bigger job as you have to remove axles, bearing & seals to get to the shoes as it is a F250.

Medical issues have stopped me from checking. When I can I will adjust star wheel on all four drums first to see if it helps my peddle setting.

 

Yes, rear drums are a big pain. Especially when you have some physical restrictions.
And the one time I had trouble with my brakes it turned out the rear brakes were doing all the work and had worn out prematurely.
Like very prematurely!

With all my other vehicles, drum or disc, the fronts wore out first and I might go through two or three sets of fronts before needing a rear replacement.
That time I went through two sets of rear shoes while the fronts showed no wear at all.
Obviously something amiss…

Just by way of saying it is probably worth the hassle to make sure the rears are not prematurely worn out.
Of course, when diagnosing a braking problem, everything is worth checking.

 

1TBC - Ya as much as I don't want to dig into the rear brake setup I need to make sure they are still good & working as they should. I am scheduled for some minor heart surgery the end of Dec, (is there such a thing as minor heart surgery?). Won't be driving the truck for month or two, maybe get back to brakes in Feb. Thanks for the comments. Tom

 

Before you bleed them you might consider replacing all the rubber brake hoses. I have heard of a brake hose sucking in air but not leaking fluid. Plus, one or more hoses may be expanding during brake application.