Pedal real low

Tiny
97CAVALIERZ24
  • MEMBER
  • 1997 CHEVROLET CAVALIER
  • 2.4L
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 225,000 MILES
The brake pedal goes almost to floor, it would stop the car. Pads and shoes are about 50% or less. Have tried bleeding the brakes starting at the master cylinder/ABS unit. I read about the gear timing on the ABS pump and followed the Haynes car manual, the ABS and Brake light are now off {after adding brake fluid. What I would like to know is can I buy a regular brake master cylinder an eliminate the ABS System? Would I nee to go to a salvage yard and get the proportioning valve and brake lines up to master cylinder, or should I buy a new master cylinder and try to replace myself? I am an experienced mechanic but never messed with ABS unit before. Basically needs a new master cylinder, but not sure if gear timing is where it should be to perform bleeding procedure! Please help! {Jim} Thanks for your time!
Sunday, February 26th, 2017 AT 4:08 AM

4 Replies

Tiny
STEVE W.
  • MECHANIC
  • 15,237 POSTS
Replace the master cylinder, bench bleed it, then throw your scan tool on and do an ABS motor he-home. Now bleed the ABS unit, do the rear bleeder first, then the front. Then you can bleed the rest of the system.

In your case the problem may simply be air in the ABS unit, it loves to hold air.
Use the scan tool to cycle the ABS motors two to three times each, then cycle the solenoids five to ten times. Now re-bleed the system.

If you do not have those functions or the scan tool, an alternate method it to just start the engine, let it run ten to fifteen seconds. Repeat this four to five times. This runs the ABS through a system test each time and will usually get any air out.

A quick way to tell if the air is in the ABS unit or the regular brakes is to pull the wiring connections off the ABS unit and step on the brakes. If they are still low, the issue is in the conventional brakes as that disables the ABS (it will trigger the ABS light and set a code as well but it is an easy test)

As for replacing all the parts be advised that can really bite you if the vehicle is involved in an accident.
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Thursday, February 25th, 2021 AT 9:48 AM
Tiny
97CAVALIERZ24
  • MEMBER
  • 3 POSTS
I do not have a scan tool, there are two bleeding valves facing front of car and four brake lines on drivers side of ABS unit. Do I remove the Master cylinder and ABS unit as one assembly? Separate them then bench bleed new master cylinder then reinstall ABS unit to new master cylinder put back on then cycle (start) engine for twelve seconds three or four times then start bleeding at the two bleeder screws in front of ABS unit then Lines starting from front to back on ABS unit, then to wheels? Is that correct? Thanks for your time!
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Thursday, February 25th, 2021 AT 9:48 AM
Tiny
97CAVALIERZ24
  • MEMBER
  • 3 POSTS
Is it possible to convert to regular power brakes, by buy new master cylinder for car without ABS? Would I need to get a proportioning valve? Thanks for your time!
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Thursday, February 25th, 2021 AT 9:48 AM
Tiny
STEVE W.
  • MECHANIC
  • 15,237 POSTS
If you are replacing the master cylinder because of the low pedal, try bleeding it as I outlined above. If it is because of it not holding pressure then it is probably bad.

To replace it you will need to get a scan tool that can do the ABS gear tension release function. If you do not do that the motor unit may be damaged. Then you remove the ABS and master cylinder as a unit. Put it on the bench, remove the bottom ABS cover, then the ABS motor pack. Next remove the banjo bolts and you now have the bare master cylinder.

Replace the master cylinder by reversing the process. When you install the motor pack turn each motor counterclockwise till they stop. Then bleed the system as above.

It is not possible to convert it over with factory parts because they did not sell that car without ABS for that year and the brakes are designed to work with the ABS. You might find an after market kit to do the job but you can probably buy a scan tool and all the parts for less money.
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Thursday, February 25th, 2021 AT 9:48 AM

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