75 brake issues

cdaye

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I have a 75 Bronco with drums all around. I’ve been having problem with the brake not applying. Pedal won’t go to the floor, but has limited braking. No leaks found. I have replaced all the brake lines, wheel cylinders, and master. I’m positive I have it bleed. The only thing not replaced is the proportioning valve and I can’t find a replacement. I searched and found this may also be called a pressure differential valve. Can this valve be rebuilt or does anyone know of this problem. I used to have good brakes.

 

Bully Bob

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Hi cdaye..,

A couple questions.. Do you have good experience working on power/non power hydraulic brakes.?   BTW., which do you have.?

Is the pedal hard when it stops moving or "squishy"..?

"pressure differential valve" (porp. valve) is simply a "restrictor" ...., allowing LESS pressure to the rear so in medium/hi braking.., the back wheels won't lock up/skid.  These rarely fail.  However, they can get plugged with improper fluid maint.

You likely have the dual M/C ...?   They can be tricky to fully bleed.   Also, the brake peal "push-rod" has to be adjusted properly or the M/C won't re-set correctly when pressure is released.

Were the "good brakes" present B/4 you did these up-grades.?  New shoes yes/no.?

---- "OVER" ----

 
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cdaye

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It is non-power. I’ve done brakes before. I did bench bleed the mc before putting on. 

It is a dual reservoir. The issue before replacing the last mc (after replacing lines, wheel cylinders etc. during restoration)was if driving for awhile and you hit the brake, it would go to floor, but would pump up and work with constant use.

Before all the lines, cylinders etc. replaced, not sure if they worked because that is when I got it and did the restore.

Now the brake pedal goes toward floor and hard, but can’t pump up.

Not sure what you mean by the push rod having to be adjusted. I don’t remember there being an adjustment.

Chuck

 

Bully Bob

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My bad.., mine has no adj. either.   (must have been the Land Cruisers)

Where you're at now.., sounds like the M/C still has issues.

When I do drum brakes.., I put the drums on with the shoes lightly rubbing the drum when turning the drum by hand. That way, you don't have to mess with that adjustment tool.  (they will break-in soon anyway) That's the only other thing that would cause what you describe. (way too loose shoes)

EXCEPT.., you can get a new/faulty M/C these days.

PS  When you bled the wheel cyl. did you do right rear, left rear, right front, left front..? (this usually insures no air in the lines.)

WHEN are we gonna see some (resto-rig) pics...?????   :- :- [-o< :D/

 

cdaye

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Yes, I did bleed in the sequence stated. I got the mc at Autozone, so I’ll take back and exchange and do the pads like you stated. I think that is what I did though.

I’ll post some pics later.

Chuck

 

cdaye

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Just an update. I pulled the proportion valve to clean out. So far i haven't been able to get the valve out of the housing. i'm soaking it in penetrating fluid and tried hooking air up after blocking ports. Not budging.  Any ideas on removing?

Chuck

 

cdaye

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I've been soaking for several days and still get the valve. i was able to get a pair of needle nose and pulled and atill not budging.

I'd like to replace, but can't find a drum only original valve. Does anyone know where to find one or will the drum/disk valve work that eveyone sells?

Chuck

 

Rons beast

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Hey Chuck,

Proportioning valves are not serviceable for us home mechs....and with a problem such as you describe the valve would not be the culprit.  It could cause other problems such as sticking or uneven braking but not a low or soft pedal.  

As Bully eluded: Your issue is either air trapped in the system, ( did you bench bleed the MC)?  or a faulty master cylinder, and/ or brakes far out of adjustment.

Good Luck

 

cdaye

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Sorry guys, I have been busy and unable to work on the Bronco ?. Got another proportioning valve and MC, but stupid me I forgot to label everything. Does anyone have a diagram or instructions for hooking up? It is all drum and has the attached proportioning valve.

Thanks Chuck

Proporting valve_E3TZ-2B257-A.jpg

 

Bully Bob

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Forget that...,  I just looked in an old book. 

The primary valve is on the "rear" of the MC.  The secondary is on the "front".

I'm assuming the rear brakes are the secondary.

As for the proportioning valve..., I'm not sure. Maybe when installing the lines, they will line up with the correct holes on the valve.  (assuming they're orig. hard lines)

 
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