Brakes: someone please explain this to me

Swap the drums side to side as well, if you can't get them turned or new ones.

 

that is also on my list for this weekend.

 

Don't forget the brake hoses.

 

Another 2 cents on the hoses.
Faulty hoses can act like the ratcheting parking brake handle. Evey application forces fluid beyond the constriction. The constriction keeps the fluid from returning thus keeping the wheel cylinder in a partially applied state. Another application and there is more pressure applied to the brake. Since the shoes were restricted from returning to the adjustment stops they start from a position closer to the drum. Another application and more movement, pushing the shoes ever closer to the drum. Eventually sometimes very quickly they are resting on the drum. This causes overheating, binding, "locking up".
If left over night the pressure of the brake shoe return springs may force fluid back past the constriction giving more normal braking at a later time.

So with the faulty brake adjudted to a position of being fully relaxed; shoes as far away from the drum as possible. Jump in start her up take off down the street and start braking. A little weak, maybe pump a few times, she slows and stops just fine the pedal firms and everythings seems OK. Start out and a couple more stops, Its locking up. Only on one side, seems to be draging. etc...

If you cook it long enough, the drag will over heat the drum, blueing it and probably warping it. Enough heat and the cylinder rubber may fail. Enough heat and you had better repack the bearings.

After fixing all that stuff a 12 dollar hose if not replaced will cause the same thing to happen again.

A thousand appologies about going over it again.
I work at night and with little else to do, I work on my hunt and pecking technique.

Looks like a three beer job to me. Cheers keep us informed on the prognosis/diagnosis.

 

Allllllrighty then, here we are 2 weeks later...

Sunday I investigated my brake system, I found:

one back wheel cylinder leaking
one partially crushed brake line
one side of rear brake shoes appear to be a different material than the other
1/4 inch of mud in the bottom of the master cylinder

I tore into it and replaced:

all 4 wheel cylinders
rear brake hose, there is only one (couldn't get the ones for the front)
speed bleeders on the front (couldn't find them for the rear)
all brake lines with prebent stainless (can you say bottom bling?)
all brake shoes
master cylinder
removed self adjuster hardware from rear brake.

Results:

pedal has good pressure
rear brakes work together
front brakes do not do much
I have bled and bled until the cows came home and cannot get pressure on the fronts.

before you ask:
I bled the master cylinder before install
I did not touch the surfaces of the new shoes
the drums are true and clean
there are no signs of leakage from any of the wheel seals.

my current theory: my speed bleeders may be crap and leaking air back into the system..

 

the shoes ride up against little pads on the backing plates
are there grooves in the pads that are keeping the shoes from moving freely?
in other words, with the drums off, you should be able to hit/move the shoes from front to rear, at least as far as the hold down hardware will let you.
short shoe to the front on all 4 wheels
adjust the linings to where you here them hitting the drum as you spin the wheels.
listen for high/low spots as you turn them; should be steady noise 360*

 

statement seems to contradict the results

my only other thought
kinked or plugged front metal brake line

 

the front brake tee on the front axle
take the lines off and push the pedal
got brake fluid?
take each line off one at a time at the front wheel cylinders
push pedal
got brake fluid ?

 

only removed one line at a time te prevent that from happening

 

fast pumping will bring it up some, then it will slowly go down a little when held

 

All good ideas, I will try it all when I can get back to it :stout:

 

I suppose you really can't rule out the replacement m/cyl either
that would be the very last step if all else checks out IMO

 

this is the problem. you need larger line to the front (5/16" vs 1/4") or a restricting device(s) on the rear lines (piece of 3/16") to counteract the smaller pistons.

 

hmmm
I am thinking all the factory steel lines are the same size, ID that is.
The wheel cylinder IDs are correct for the application IMO.

So 66CJ5, you are saying larger line size to the larger cylinders ?
I'm not following your train of thought on this, the part about restricting the flow to the smaller rear cylinders.

 

I Have brakes!

the $ sink has been sitting under a tarp for nearly a month and a half while I try to find time and a plan to fix my ailing brake system. if you have followed this I wound up replacing almost the entire brake system from the MC to the shoes. only to have my front brakes not work at all. well I went through the old MC, cleaned and checked it out and there was nothing wrong with it short of the 1/4 inch of mud in the bottom. cleanded it again and reinstalled.

The "New" MC is on the bench now awaiting disection:twisted:

after a little bleeding (the brakes not me ) I now have 4 operational brakes...

I drove it out of the neighborhood safely for the first time since July:stout: :stout:

 

Sweet Randy

 

Here we go again:

since our last episode, I verified the correct ports on the MC and switched the lines to match the new setup. went over all lines and hoses to make sure all is tight and hooked up correctly. refilled the MC and pumped a few times to work out any air near the MC. bled the brakes from farthest to nearest to get out as much air as possible. got some pedal but not much, so I tried it out to see if all 4 brakes work. well, when I pump up a little, all 4 are working... we are getting there.

tried to bleed again and got no air out of the rears or the passenger side front. but when I tried the drivers side front I got a large bubble. AH-HA! I had it, so I put a helper on the pedal and began bleeding that brake exclusively...

here is where the story gets weird and I believe I may be breaking a few laws (of Hydraulics). with helper pumping slowly on pedal, down the hold, release pressure, close bleeder, let pedal up... I get a nice big spurt of air each stroke. well this goes until I have dropped the level in the MC 1/2, refil and begin again... here we are an hour later, I have pumped about a cup of fluid through the lines to that one brake and I can still get a good spurt of air out of each stroke....

now the first thought is a leak somewhere, but with a couple of hundred to several thousand PSI inside a brake line, and only about 14.7 outside, anywhere air can be sucking in, something has to leak out. and at the volumes of air I am seeing, I should be sitting in a lake of brake fluid... but there is no sign of leakage anywhere.

I do not see how the MC can be leaking air in and not fluid out, but I am open to whatever ideas you may have....