spongy and soft brake pedal

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  #1  
Old 04-03-02, 01:27 AM
K-dog
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spongy and soft brake pedal

I have a 1991 Toyota 4 wheel drive pick up. It is extra cab, with the 3.0 liter V6. My brakes have gotten really spongy and soft. I cannot lock them at all no matter how hard I push the pedal. I have replaced the pads, shoes, master cylinder, wheel cylinders, adjusted the rear shoes and they are still no better then before. I have used a one man brake bleeder to bleed the brakes at the wheels and bench bled the master cylinder too. Still same pedal action. Could the flexible hoses be swelling under load? Or might this be a check valve problem? I am at wits end here and would really appreciate any help or comments. Thanks much, k-dog
 
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  #2  
Old 04-03-02, 05:23 AM
Joe_F
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Sure. Or you didn't bleed it completely.

You must have a steady stream of fluid with no bubbles or spitting coming out of all the wheels. You must also bench bleed the master cylinder before you install it.

Refer to a service manual for more detail. Check the links in my signature file for some ideas or get a manual for your truck from the library or parts store.
 
  #3  
Old 04-03-02, 10:02 AM
K-dog
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response

Joe, I have a factory Toyota manual and followed it to a tee. Yes, I bench bled the master cylinder and yes I got all the air out of the system. I ran 3 quarts of dot 3 thru the system and I used a power brake bleeder. There is no entraped air in the lines whatsoever.
 
  #4  
Old 04-03-02, 10:25 AM
Joe_F
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At this age, I would surely suggest you change the flexible hoses as they rot from the inside out and act as a check valve.

The only other thing I can think of is a stuck proportion valve, but let's not go there yet.
 
  #5  
Old 04-08-02, 07:27 PM
HJTF
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Spongy brakes

Does brake pedal come all the way up? Have you replaced the master cylinder push rod? How much slack in pedal travel before you feel contact to master cylinder? Are brake lines straight down from master cylinder with no upward bends?
 
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