Help with brakes.......

vvg · December 15, 2006

This is my 1st post. My grandfater left me this 1990 Ex cab Chevy truck with 30K original miles, It has 60K on it now. The pass side brake was grabbing. So I replaced the caliper and pads on both sides... Couldnts get it to work (soft pedal) so I replace the Master cylinder. I bled it . (Althought the MC did not come with the little hoses just plugs to bench bleed it) Now the pedal feels pretty good but when you start the truck the pedal goes to the floor. I blocked the back brakes off (front part of MC) with the plastic plug that came with the MC. And when you pump it the fluid for the front is saturated with air bubbles to the point it looks milky that goes away after 10-15 minutes. Am I doing something wrong? Ive done alot of brake jobs on my cars but have never run into a prob like this. I think it has some kind of Crude ABS on it ( I may be wrong) Could it be the brake booster? This is really strange. I sure would appreciate the help . thanks!!!!!!!

GM-Tech · December 15, 2006

And when you pump it the fluid for the front is saturated with air bubbles to the point it looks milky that goes away after 10-15 minutes.

Sounds pretty obvious that air in the system is your problem. How it's getting in there, I don't know. Maybe it was never bled completely. Did you replace the little brass washers that go on the caliper hose where it bolts to the caliper? Though very rare, it can allow air to be sucked in without fluid leaking out, if those washers aren't in perfect condition.

vvg · December 19, 2006

I had my wife pump the brakes with the motor on and it was leaking from the washers like you said and the bleed valve was sucking air too. replaced both so far so good. The new brake pads are also "beveled" Not all of the surface is touching the rotor. It looks like they are made that way on purpose. Not sure why?? Only the top , bottom and center are actually touching the rotor. After it wears down It will all be touching.... Anyway it gave the illusion the piston was not compressing the pads fully in.

thanks

Keith

Ps Is it normal to get all that air in the master cylinder and or lines if you pump the brakes fast with the motor on? Where the fluid gets milky looking from all the air. Or is that a leak in the system?