ABS problems

how would you test an electro-hydraulic control unit to make sure it works properly?

i don’t seem to have very much pressure going to my back brakes.

What year Olds Bravada? How many miles? When were the brakes last inspected or serviced? How are you determining that you have insufficient pressure going to your back brakes?

it’s a 2000 with 165000 miles on it.I’ve changed the booster,master cylinder,rear caliper,and brakes in the last week.

ABS units self-test themselves every time you turn on the key…If a fault is detected, the ABS warning light will stay on…

It might be cheaper to have a professional brake mechanic diagnose and repair your car instead of throwing expensive parts at it hoping you find the right one…

On most FWD vehicles, 80% of the braking effort is supplied by the front wheels. So pressure to the rear brakes is limited by design…

How is the pedal? mushy? why did you do the rebuilding? what were the original symptoms?

are you certain you have completely bled the brakes? also, did you correctly adjust the rod in the brake booster, where it goes from the brake pedal into the booster?

A friend of mine rebuilt his jeep, and was complaining about the poor braking and he just couldn’t get them to stop being mushy. I discussed with him how the bleeder valves are the key, and offered to go help him, pump, while he opened an closed the valves. While discussing how the air goes to the TOP of the bleeder he got a glazed look in his eyes. he put the calipers on UPSIDE down. oops. BUT just to show how a simple made in haste mistake can mess up the progress.

ADJUST THE ROD??? how would you do that??

the rod which is attached to the brake pedal is adjustable by the two nuts. when replacing a MC you can’t assume the old rod is correct for the new MC. if you don’t have full ‘throw’ you aren’t getting all the air out of the MC when you pump the brakes to bleed them.
it may be only a turn, maybe a turn and a half, but you must cover ALL the bases when doing a replacement like that. you did bench bleed the MC prior to installation?

are you using a manual to guide you?

I asked about the original conditions that made you do the replacements. more info helps decipher what is happening. not trying to be critical or wise, more info is better. its pretty hard to decode over the computer screen as it is with partial info.

the only rod attached to the brake pedal is from the power brake booster.the reason i did all this work is bad advice from a so-so mechanic.

That is the rod I am referring to. It is not simply a pull the MC and booster off, and slap another one on. it has to be adjusted.

what exactly is the problem with the brakes? what WAS the problem with the brakes? you mention the proportioning valve. and you mention ABS. Is the ABS light on (and doesn’t go out)? Have you made sure you didn’t whack the ABS sensor out of tolerance from the brake hub when you were replacing the caliper/cylinder? Was there an ABS light showing first that made you look for help/repairs?

Im sort of thinking that if you cannot answer the basic questions about ‘why,’ and ‘symptoms’ that you should take it somewhere and have a pro troubleshoot it!

clarity and info…

the only time the ABS light was on is when the front wheel bearing was bad.i didn’t realize i had any brake problems until i went to the before mentioned mechanic.he told me that my booster,and MC was bad,so i changed them.to adjust that rod(i don’t know about “those two nuts”)could i just turn the rod from the booster itself?

can’t thank you enough! never would have known to make adjustment to booster.

             thanks again!!!!!