brake pedal slowly leaks down

1996 GMC SIERRA
152,000 MILES • V8 • 2WD • AUTOMATIC
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HOOTERMAN10
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I have 96 model gmc pickup and the brake pedal slowly leaks down.I have replaced brake booster and MC still have same problem does any one know if it could be my ABS unit failing? Is that a symtom of ABS unit?
Jun 9, 2010 at 7:05 PM
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RASMATAZ
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Hi hooterman10, Welcome to 2carpros and TY for the donation

If there's no leakage anywhere and was bleed properly could be the ABS unit-bleeding sequences start at the MC, ABS modulator then wheels. Could be the new MC leaking internally though its new-been here before
Apr 14, 2021 at 1:36 PM
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HOOTERMAN10
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I have put 2 remanufactored and now a brand new MC Its got to be something else. Can I completely eliminate the ABS unit by installing a upper proportion valve?
Apr 14, 2021 at 1:36 PM
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RASMATAZ
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Did you bleed the modulator if not try bleeding it and see what happens-as for the proportioning valve never done it who knows it might work
Apr 14, 2021 at 1:36 PM
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HOOTERMAN10
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I am told I need a scanner to open valves in ABS unit to purge air out does this sound right ?
Apr 14, 2021 at 1:36 PM
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RASMATAZ
  • ✓ASE Certified Mechanic
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Yes sir
Apr 14, 2021 at 1:36 PM
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