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Power brake booster

i have a 2000 Bravada,and it seems that only one piston of the duel piston brake caliper is working.would a faulty brake booster cause this to happen,or should i be worried about somethjng else?

The brake booster will have nothing to do with it. This will be a problem in the caliper itself, or perhaps in the brake line leading to it. The brake booster just helps the pedal apply force. Other than that it has no direct effect, and couldn’t affect only one part of a caliper.

what if it sounds like air leaking whenever i step on the brake?

If your brake booster was leaking that badly then your engine would likely stall or at least nearly so whenever you stepped on the brake.

However, a normally functioning brake booster does work by a leak - of sorts - a purposeful one. When you step on the brake it lets air rush into it - the difference in pressure between the air coming in and the vacuum on the other side of a diaphragm is what makes the brake booster work.

Look at this: http://auto.howstuffworks.com/auto-parts/brakes/brake-types/power-brake2.htm

Why do you say “it seems that only one piston of the duel piston brake caliper is working”? How do you know this?

when i pulled the tire off,the wear on the rotor only looked like it was only from the lower piston pushing on the brake shoe

Well now you’ve confused me. The two pistons each should press on the entire width of the rotor, so I don’t see how the rotor’s wear pattern would indicate one or the other piston isn’t working. Is this what it looks like?

I would also assume that it wouldn’t show on the rotor - though it would likely show in the pads - perhaps worn unevenly back to front or vice versa.

can’t really tell too good by that pict.,but yes.

duhh.i don’t know why i didn’t check the pads

OK. Please describe as completely as you can what you saw when you looked at the rotor. Also, are the brakes making any odd noises (besides the air noise)? How well do they slow you down? Has it changed lately?

it looks to me that the rotor is only wearing on the bottom.there is no unusual noise.i just replaced all calipers last year.i wish it would slow down better

OK…where is ‘the bottom’ of the rotor?

okok,imeant to say the half closest to where it mounts on the studs.as if only one piston is working.

OK, now I get it. Each piston pushes across the entire surface of the rotor, so it’s not that one isn’t working. The caliper itself may be jammed or cockeyed. It definitely needs something fixed, you may want to go to a brake shop.

ps - it also could be that one piston is frozen/jammed, messing up the pad alignment. Either way, you’ve got to get the caliper off and check it out, along with turning or (preferably) replacing the rotor.

The rust crept outward from the inner edge of the pads. If it isn’t too deep or the rotors aren’t worn out, you can have them resurfaced. Changing the rotors is easy once you get the caliper mount off. Those bolts may be tight because they require over 100 FT LBS of torque. I recommend new rotors.