Bleeding brakes

Tiny
TBIRD62
  • MEMBER
  • 1996 CHEVROLET CAVALIER
  • 2.2L
  • 4 CYL
  • FWD
  • MANUAL
  • 260,000 MILES
While bleeding the brakes I tripped the valve in the master cylinder and now can only get brake fluid out of right rear and left front. In a previous post you wrote that this happens when the brake pedal is pushed more than half way to the floor and that a lot of master cylinders get replaced for that reason even though there is an easy fix. What is the easy fix? I would really appreciate any help.
Thank you, Bob
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Saturday, March 4th, 2017 AT 10:59 AM

4 Replies

Tiny
KHLOW2008
  • EXPERT
The master cylinder seems to be bad. You would need to disassemble it to check the seals and replace them if the bore is not worn. Otherwise you would need to replace the master cylinder assembly. Even if you had not depressed the cylinder fully, there is a possibility the cylinder might give way sooner or later as they wear out over time.
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Sunday, March 5th, 2017 AT 7:45 AM
Tiny
TBIRD62
  • MEMBER
Thank you for your reply regarding my 1996 Cavalier brake bleeding problem. I am going to install a new master cylinder. I have another problem that I would appreciate your expertise on. The master cylinder has the ABS unit mounted directly to it. It has o-rings between them that I believe should be changed but the o-rings only come with a new ABS unit which is very expensive. Do you know where I might go to get the correct o-rings? The local auto parts store did not seem to know where to get them. Thanks again for your assistance. I really appreciate your help. The car is not worth anything but it still has plenty of life left in it!
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Monday, March 6th, 2017 AT 9:53 AM
Tiny
TBIRD62
  • MEMBER
I replaced the master cylinder and I still cannot get the RF and LR brakes to bleed. Any suggestions would be helpful. Thank you!
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Monday, March 6th, 2017 AT 6:42 PM
Tiny
CARADIODOC
  • EXPERT
Hi guys. KHLOW2008 was referring to the damage that can occur to the lip seals in the master cylinder when the brake pedal is pushed over half way to the floor. That should be avoided with any master cylinder that is more than about a year old, but on GM front-wheel-drive cars, that is what trips the valve and blocks two ports, presumably the one with an external leak and its diagonal opposite.

A lot of people believe that valve won't trip if you pedal-bleed in a specific sequence, but if you think about it logically, that valve trips for a leak in any of the four circuits, so it will trip when any of the four wheels is bled first.

The only way I have ever found to reset that valve is to go to one of the two wheels that isn't flowing any fluid, open just that bleeder screw, then give it a short, quick burst of compressed air. I use a rubber-tipped air nozzle, and give it a quick whack with the side of my hand. The cover should be loose on the reservoir. After that, just let it gravity-bleed. Once you have fluid flowing from all the wheels, and the bleeder screws are closed, "irritate" the brake pedal a little, by hand, then open each bleeder screw one at a time again to let the last few remaining air bubbles out.
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Tuesday, March 7th, 2017 AT 9:00 AM

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