bleeding abs system 2004 gmc envoy
when braking. the pedal was low and started pulsating as if the abs was
activated when coming to comply stop... After some time the front right side
caliper started leaking and in need of front brake pads and rotors...
Replaced the caliper, pads and rotors on both sides, tried bleeding brakes
but the pedal was soft and would travel to the floor... Decided to change
master cylinder. (bench bleed before installation).Did a complete fluid
flush... Now with engine off, pedal very hard and very little movement, witch
is normal because the master cylinder is not assisted with the brk booster...
Bleeding with engine running several times and pedal would not hold
pressure and would travel the the floor... Because the front and rear
wheels are removed I attempted to reset abs module by having all four
wheel to turn freely on the 4x4 low position, would also accelerate then
brake but what would append is when accelerating and lay off the
accelerating pedal the engine would rotate to over 5 to 6 thousand rpm, at
that point the brake pedal was high and at the same time a very noisy
pulsating brake pedal to the point where I would feel it when putting my
hand on the master cylinder and the brake booster then eventually the rpm
would drop but wheels still turning but brake pedal would not hold pressure
and would travel to the floor... not sure what to do next?
Check and see if you have a faulty speed sensor and check your steer angle sensor and make sure ignition voltage is good and on abs pump motor. Could have a faulty abs module. If everything is ok. I would do a power bleed on abs motor. You will need a scanner that can access that. Follow procedure of abs operation. Once power bleed is completed. Bleed all 4 again with vehicle off starting with furthest wheel from mastercylinder.
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