Brake problem

[bj58]

The other day my rear driver side brake locked up, by the time I pulled over it was smoking a little bit. I had to hit the brakes hard to keep from nailing a car.
I replaced the piston(the thing that pushes the pads out) not sure of the proper name.
I thought this fixed the problem but not so sure now.

When I'm driving it fills like the brakes are building pressure. Hard pedal to push. If I push it down harder it stops the truck just fine, but when I let off it still fills like the pedal is slightly pressed down. How ever some times it works fine, has a soft pedal until about half way down then starts stopping.

Is my master cylinder going out?

 

[riotwarrior]

I'm guessing....just a guess, that if your pedal effort has increased your seeing an issue with vacuum booster....not MC...

 

[bj58]

How would I go about testing it?

 

[stumiister]

If you push the brake pedal down do you hear any noises like a whistle sound near your feet or the floor inside the truck or maybe a woosh sound , that is the booster with a vacuum leak.

 

[79jasper]

Does you heater work in the vent position? Or does it only blow out the defroster vents and floor?

 

[riotwarrior]

Removing the vacuum line from the booster and attempting to press brake pedal should show if similar effort as well.

If the vacuum pump is not creating enough vacuum it may be at fault too.

You should be seeing close to 20 inches vacuum IIRC with a gauge.

I'm sure someone will chime in here with some more suggestions.

Al