proportioning valve/combo valve woes

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smurph20

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If the old M/C was leaking at the mounting point the fluid might have eating the diaphragm in the booster enough for it to be leaking vacuum causing your squishy pedal.
 

1low4x4

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Forgot to mention the booster is new. Replaced it last weekend with the mc
 

1low4x4

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Only thing I can think to do is pull the wheels and looks at the wheel cylinders? To see if ones leaking, now rhat tbere is pressure there?

Wpuld that give me a squishy pedal?
 

SlickGTP

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Air in the system or a leak somewhere...
 

1low4x4

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Well, ended up bleeding again, and again, no air really. Took the rotors off again and nothing was leaking. Adjusted the brakes in the back which helped immensely.

The pedal is still not super stiff...but I can tell it stops better, and the brake light is not on and it has pressure at the rear when I bleed them. All that matters!
 

GreaseDog

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That was going to be my suggestion. "self adjusters" don't work for ****. My 94 has been terrible about this. At least once a year, I have to pull the drums and adjust the rear brake shoes. After that, pedal comes back up, and it will almost put you in the dash (3/4 ton rear brakes, 1/2 ton prop)
 

chengny

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Wpuld that give me a squishy pedal?

A couple of often overlooked reasons for a low/spongy pedal feel:

Spongy Pedal


CAUSES


•Air is trapped in the hydraulic lines. The spongy feeling is a result of the air being compressed when the brakes are applied. Clean fresh brake fluid is non-compressible and will produce a firm brake pedal.

•Brake fluid is contaminated with water. During prolonged or severe braking, localized brake fluid temperatures can quickly exceed 220 degrees F. Any water in the brake fluid boils off into steam and creates a spongy pedal. As the brakes cool off the steam condenses back into water and the spongy feeling disappears.

•The rear drums are worn to thin. The spongy feeling is a result of the drums actually flexing into an oval as the brakes are applied.
WHAT TO CHECK FOR


•Verify that the master-cylinder reservoir is filled with clean fresh brake fluid.
NOTE: If at any time the master-cylinder reservoir has been emptied, the master-cylinder will need to be bled.



•Remove the rear drums and measure the inside diameter of each. If either drum exceeds the maximum diameter specification, both must be replaced.
NOTE: Always replace both drums on an axle. Replacing only one drum will result in a different braking ability from side to side. This will produce a steering "pull" when the brakes are applied.

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•If the brake pedal is still soft or spongy, flush the hydraulics and replace with clean fresh brake fluid, then bleed the brakes at all four wheels again.



•Verify that the shoes/linings are properly adjusted, adjust if necessary.
•Bleed the brakes at all four wheels.
NOTE: Refill the master-cylinder after bleeding at each wheel.


Low Pedal


CAUSES


•Excessive clearance between shoes/linings and drums. The brake pedal will feel solid and the vehicle will have sufficient braking power, but the pedal travel will be excessive (greater than 1/3 of total travel).
NOTE: If the brake system is operating properly, the amount of pedal travel is proportional to the distance that the brake system has to extend the pads or shoes. This distance is normally controlled by the adjustment of the rear shoes/linings, since the disc brakes readjust themselves with every application. Keep in mind that if the shoes/linings are loose, the emergency brake will also be loose, since it applies the rear brakes.

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•Excessive lateral runout (rotor wobble) or loose wheel bearings. The pads/linings can be knocked further back into the calipers than usual by excessive rotor wobble. This requires more brake fluid behind the pistons to extend the pads back into contact with the rotors. This results in longer pedal travel.
WHAT TO CHECK FOR


•Check the adjustment of the rear shoes/linings, and adjust if necessary.
NOTE: The shoes/linings are normally automatically adjusted. If you have to adjust the brakes more than once, you should inspect the operation of the auto-adjusters. Remove, clean, and lubricate the automatic adjusters as necessary.



•Check the wheel bearing adjustment, and adjust if necessary.
•If a pedal pulsation is also occurring, inspect the rotors for excessive lateral runout. Resurface or replace if necessary.
 

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