Cannot get brake fluid to two lines on a 1993 Chevrolet Cavalier Z24

Tiny
JASON1979
  • MEMBER
  • 1993 CHEVROLET CAVALIER
  • FWD
  • MANUAL
  • 183,000 MILES
I have a 1993 Chevrolet Cavalier Z24 3.1L with ABS. I cannot get brake fluid into the lines on the front passenger and rear driver calipers. I have tried to bleed the system both by conventionally and gravity methods. How can I get fluid to the lines so that I can have brakes?
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Sunday, April 24th, 2011 AT 8:38 PM

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Tiny
CARADIODOC
  • EXPERT
On GM vehicles with the step bore master cylinder, imagine a teeter totter that is level, but if it moves one way, it will block the ports for two wheels. The teeter totter moves when one hydraulic circuit builds pressure and the other one doesn't due to a leak or from pedal-bleeding the system. As soon as the pedal is pressed while a bleeder screw is open, the teeter totter moves to block the ports for one front brake and the opposite rear brake. No fluid can be forced out of those two bleeders.

If the system is left like this, one front brake will wear out very quickly and the other side will look like new. People usually ask for advice when they run into worn pads on one wheel for the second or third time. The car will usually not have a brake pull because alignment angles are modified to accommodate loss of one hydraulic circuit on the split-diagonal systems.

The only way I ever found to reset the valve in the master cylinder, (that teeter totter), was to give a quick, short burst of compressed air to one of the bleeder screws that isn't flowing. Don't use so much air that it makes its way up to the master cylinder. A fraction of a second is sufficient. After that, just let it gravity bleed.

The same problem can happen even when the hydraulic system wasn't opened. After installing new front pads, the pistons must be worked out until the pads contact the rotors. One piston will always move first, then, once contact is made with the rotor, pressure will start to build up. That will trip the valve at which point the other piston will never move. Once the burst of air is given and the line gravity bleeds, pressing the pedal no more than half way to the floor will prevent the valve from tripping again.

This same master cylinder can be used with the factory "add-on" ABS system that is bolted directly to the ports of the master cylinder.

Even with normal master cylinders, you should never press the brake pedal more than half way to the floor when pedal bleeding. The lip seals will be torn on the debris and corrosion that build up in the lower half of the bores where they don't normally travel.
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Sunday, April 24th, 2011 AT 8:53 PM
Tiny
JDL
  • EXPERT
Just to add, you don't have integrated ABS, correct? That pressure is dangerous. A non integrated abs shouldn't be dangerous, as far as fluid pressure. I was just looking at some info, without a tech 1 scanner, You bleed the front first, drive the vehicle at least 4 miles an hour, that should intialize the abs and you get fluid to the rear.
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Sunday, April 24th, 2011 AT 9:32 PM
Tiny
WRENCHTECH
  • EXPERT
This is a cross-bleed system so the RF and LR are separate circuits in the master cylinder. You must have let the master go dry in one of the reservoirs and now it won't get primed. It may help if you crack the lines open in the master until you get fluid flow from all lines. A pressure bleeder would be very helpful.
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Sunday, April 24th, 2011 AT 9:37 PM
Tiny
JDL
  • EXPERT
Fluid level is always good to check, lol.
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Sunday, April 24th, 2011 AT 9:43 PM
Tiny
WRENCHTECH
  • EXPERT
The way I meant to word that is the RF and LR are the SAME circuit and the LF and RR are the other circuit so you have lost 1/2 of the master cylinder.
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Sunday, April 24th, 2011 AT 9:46 PM
Tiny
JASON1979
  • MEMBER
The ABS system was factory installed not an "add-on"
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Sunday, April 24th, 2011 AT 10:30 PM
Tiny
JDL
  • EXPERT
Have you tried bleeding the front then drive a little as suggested?
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Monday, April 25th, 2011 AT 2:58 PM
Tiny
JASON1979
  • MEMBER
Yes, I have tried driving the car at a low speed as suggested. It is an integrated ABS system installed from the factory.
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Monday, April 25th, 2011 AT 6:03 PM
Tiny
JDL
  • EXPERT
The integrated system is high pressure, you need to pump brake about 40 or 50 times before you open a brake line, to reduce the pressure.

Still no brake fluid at the rear? Any abs codes?
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Monday, April 25th, 2011 AT 6:10 PM
Tiny
WRENCHTECH
  • EXPERT
This is a diagonal system. You just need to the that side of the master primed and get fluid flowing. A pressure bleeder would do it easily.
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Monday, April 25th, 2011 AT 6:18 PM
Tiny
JASON1979
  • MEMBER
There is absolutely no brake fluid at all in the RF or the LR brake lines. I have pumped and pumped and pumped the h3ll out of them and tried bleeding but still no fluid. I had a friend that is also a mechanic to help me a little and there is fluid at the fittings under the hood but nothing in the lines. I do not have a scanner to check the computer for codes and the ABS light comes on and will go off after the car is cranked up. I will say that somehow, I had a CV Axle come apart while I was driving the car and that in turn messed up the lower control arm. I have replaced the CV Axle, lower control arm and lower ball joint. I never touched the brake system and I hung the caliper up and out of the way with wire (through the caliper) an not by the line as I have seen some people do. My friend noticed the master cylinder reservoir low on fluid so we added fluid and was going to bleed them to make sure there were no problems. It was during the process of pumping the brakes that we noticed that the brakes did not feel normal and this is how I know that there is no fluid going to the RF and LR lines.
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Monday, April 25th, 2011 AT 6:20 PM
Tiny
JASON1979
  • MEMBER
I have tried a pressure bleeder on the lines at the wheels, and I am still not getting fluid.
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Monday, April 25th, 2011 AT 6:24 PM
Tiny
WRENCHTECH
  • EXPERT
No, that's not how a pressure bleeder works. It pushed from the master out.
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Monday, April 25th, 2011 AT 6:28 PM
Tiny
JASON1979
  • MEMBER
Sorry, I must be getting too tired and aggravated over the thing. I thought you were referring to a vacuum bleeder. Unfortunately, I don't have a pressure bleeder.
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Monday, April 25th, 2011 AT 6:30 PM
Tiny
WRENCHTECH
  • EXPERT
You may want to look into finding a shop that can do that for you. You may not get it bled without one.
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Monday, April 25th, 2011 AT 6:39 PM
Tiny
JDL
  • EXPERT
You can try the rehome function, setting the pistons to home should allow fluid to brakes. If abs codes are present, this may not work.

To raise the pistons to home position without a scanner, start the engine and let it run for 10 seconds. Watch the abs lite. It should turn off after three seconds or so. WARNING, If lite doesn't go off, have to use a scanner. If lite turned off like it is supposed to, turn the ignition switch off and repeat the procedure. If the lite goes off again after three seconds, the brakes can now be bleed.

Are you tried of fooling with it yet? My info shows three channel system. One separate channel for each front wheel. One channel for both rear wheels. If you don't have fluid at one rear wheel, shouldn't have it at the other rear wheel either.
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Monday, April 25th, 2011 AT 7:23 PM
Tiny
CARADIODOC
  • EXPERT
This is a REAL common problem. As I mentioned earlier, give one of the blocked bleeder screws a short burst of compressed air, then let it gravity bleed. When you pedal bleed these GM front-wheel-drive cars, and one front piston is out and contacting the pads, it starts to build up pressure, but the side with the piston not fully extended out to the pads yet does not build pressure. Once you push the pedal more than half way to the floor like that, the unequal pressures causes the valve in the master cylinder to trip and blocks two ports. I should say it blocks the port for two wheels, exactly like you described.

GM's ABS system for your car is an add-on system meaning the same master cylinder design is used, but they add the hydraulic controller to it. It's a very inexpensive and quite reliable design and parts can be replaced in it. No one I know of has ever found another way to reset that valve except with the compressed air. Many people have the same problem with a new master cylinder after they fully press the pistons, (which is normal procedure), during the bench-bleeding process.
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Monday, April 25th, 2011 AT 7:25 PM
Tiny
JDL
  • EXPERT
I don't know why you couldn't use master cylinder cap to pressureize? Just drill a small hole, place airline in hole, doesn't leak. Add a little pressure. Most pressure bleeders I see, says start with less than 10 psi.

Maybe you can find a master cylinder cap in the salvage yard that will work? Sometimes you have to use your imagination. Just be safe and don't get hurt. If you get tired of talking to us, take it to a shop.
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Monday, April 25th, 2011 AT 7:53 PM
Tiny
WRENCHTECH
  • EXPERT
You need to force fluid through it, not air.
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Monday, April 25th, 2011 AT 7:56 PM
Tiny
CARADIODOC
  • EXPERT
Pressure bleeding won't help if pedal bleeding doesn't work. A quick shot of compressed air in either of the blocked bleeder screws is the two-second fix and the stupid thing will be done and flowing. After that, to prevent a repeat of the problem just don't press the pedal more than half way to the floor.
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Monday, April 25th, 2011 AT 8:02 PM

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