HOW DO YOU BLEED A ABS BREAK SYSTEM? WHY DOES A ABS LIGHT STAY ON? i REPLACED THE MASTER CYLINDER AND BLEED THE SYSTEM IN THE STANDERED WAY.

A master cylinder is supposed to be bench bled first to get the air out of the primary and secondary bores in the cylinder if you didn't do this there's air in the cylinder also you may have blown the seals inside it try to bench bleed it if you feel no pressure on the master cylinder plunger after bleeding it the seals are blown and you need another one ////\\\\if you do feel the pressure after bleeding and after installing it and bleeding the lines at all wheels and there is no pedal pressure the brake booster is the problem

You need a special tool to do this.

You have a defective master cylinder.

Hi there:
I suggest to check this procedure, when the hydraulic brake system must be bled whenever a fluid line has been disconnected because air gets into the system.

A leak in the system may sometimes be indicated by a spongy brake pedal. Air trapped in the system is compressible and does not permit the pressure applied to the brake pedal to be transmitted solidly through the brakes. The system must be absolutely free from air at all times. If the master cylinder has been overhauled or a new cylinder has been installed, bleed the cylinder on a bench before installation. When bleeding brakes, bleed at the wheel most distant from the master cylinder first, the next most distant second, and so on. During the bleeding operation the master cylinder must be kept at least 3 / 4 full of brake fluid.


The ABS bleeding procedure is different from the conventional method. It consists of the following three steps:
Step 1: Conventional manual brake bleed.
Step 2: Bleeding the system using the DRB scan tool.
Step 3: An additional conventional manual brake bleed.

The recommended ABS bleeding procedure is as follows:

1. To bleed the brakes, first carefully clean all dirt from around the master cylinder filler cap. Remove the filler cap and fill the master cylinder with DOT 3 brake fluid to the lower edge of the filler neck.
2. Bleed the master cylinder first. Have a helper operate the brake pedal while bleeding each master cylinder fluid outlet line. Do not allow the master cylinder to to run out of fluid,as this will allow additional air to be drawn into the cylinder.
3. Bleed the brake system in the following sequence:
   1. Master cylinder
   2. HCU valve body (at fluid lines)
   3. Right rear wheel
   4. Left rear wheel
   5. Right front wheel
   6. Left front wheel
4. Clean off the bleeder connections at all four wheel cylinders. Attach the bleeder hose to the right rear wheel cylinder bleeder screw and place the end of the tube in a glass jar, submerged in brake fluid.
5. Open the bleeder valve 1/2 - 3/4 of a turn.
6. Have an assistant depress the brake pedal slowly and allow it to return. Continue this pumping action to force any air out of the system. When bubbles cease to appear at the end of the bleeder hose, close the bleeder valve and remove the hose.
7. Check the level of fluid in the master cylinder reservoir and replenish as necessary.
8. After the bleeding operation at each wheel cylinder has been completed, fill the master cylinder reservoir and replace the filler plug.

Do not reuse the fluid which has been removed from the lines through the bleeding process because it contains air bubbles and dirt.

1. Perform the "Bleed Brake'' procedure with the DRB II scan tool. This procedure is described in the DRB II software information and diagnostic guide.
   1. Attach the DRB II scan tool to the diagnostic connector.
   2. Run the Bleed Brake procedure as described in the DRB II tester guide.
2. Repeat the conventional bleeding procedure as previously outlined.
3. Fill the master cylinder reservoir to the proper level.
4. Check the brake operation.

Hope this helps.

Probably will have to bleed the master cylinder.

Did you bench bleed the MC before installing it? If not, that's the problem. MUST be bench bled or you'll always have air. If brakes lights are on, the brake switch is out of adjustment OR (since you replaced the MC), the push rod is out of adjustment

unless the system was open there was no need to bleed the system. the Master Cylinder and the ABS unit are 2 different things. you should be able to bleed it like any other car. fill up the M/C and open the right rear bleeder, put a clear hose onto the bleeder, then you can see air come through. put the hose in a clean bottle and pump it until you see air come through, then a few more pumps, do this at each wheel. if all air is out and the pedal is not firm , the m/c may be bad.

As a general rule, if you have ABS you might have to cycle the pumps and valves to purge the old fluid out of the unit. This is either done via a dealer scan tool, a purge valve/bleeder valve on the ABS unit, or a less than ethical way. Drive your car and heavily engage the ABS, you know what I'm talking about.
Then you will need to repeat the bleeding process that you have already done.
Normal non ABS brakes, bleed once.
ABS brakes, bleed, cycle then bleed again.

MANUAL BLEEDING

For those of us who are not fortunate enough to have access to a power bleeding tool, the manual brake bleeding procedure will quite adequately remove air from the hydraulic system. The major difference between the pressure and manual bleeding procedures is that the manual method takes more time and will require help from an assistant. One person must depress the brake pedal, while another opens and closes the bleeder screws.

In addition to a length of clear neoprene bleeder hose, bleeder wrenches and a clear bleeder bottle (old plastic jar or drink bottle will suffice), bleeding late-model ABS systems may also require the use of one or more relatively inexpensive combination valve pressure bleeding tools (which are used to depress one or more valves in order to allow component/system bleeding). To fully bleed the late model ABS systems, a scan tool should also be used to run the system through functional tests.

1. Clean the top of the master cylinder, remove the cover and fill the reservoirs with clean fluid. To prevent squirting fluid, and possibly damaging painted surfaces, install the cover during the procedure, but be sure to frequently check and top off the reservoirs with fresh fluid.

CAUTION Never reuse brake fluid which has been bled from the system.

1. The master cylinder must be bled first if it is suspected to contain air. If the master cylinder was removed and bench bled before installation it must still be bled, but it should take less time and effort. Bleed the master cylinder as follows:
   1. Position a container under the master cylinder to catch the brake fluid.

WARNING Do not allow brake fluid to spill on or come in contact with the vehicle's finish as it will remove the paint. In case of a spill, immediately flush the area with water.

1. Loosen the front brake line at the master cylinder and allow the fluid to flow from the front port.
   
2. Have a friend depress the brake pedal slowly and hold (air and/or fluid should be expelled from the loose fitting). Tighten the line, then release the brake pedal and wait 15 seconds. Loosen the fitting and repeat until all air is removed from the master cylinder bore.
   
3. When finished, tighten the line fitting to 20 ft. lbs. (5 Nm).
   
4. Repeat the sequence at the master cylinder rear pipe fitting.

During the bleeding procedure, make sure your assistant does NOT release the brake pedal while a fitting is loosened or while a bleeder screw is opening. Air will be drawn back into the system.

1. Check and refill the master cylinder reservoir.
   

Remember, if the reservoir is allowed to empty of fluid during the procedure, air will be drawn into the system and the bleeding procedure must be restarted at the master cylinder assembly.

1. On late model ABS equipped vehicles, perform the special ABS procedures as described later in this section. On 4 wheel ABS systems the Brake Pressure Modulator Valve (BPMV) must be bled (if it has been replaced or if it is suspected to contain air) and on most Rear Wheel Anti-Lock (RWAL) systems the combination valve must be held open. In both cases, special combination valve depressor tools should be used during bleeding and a scan tool must be used for ABS function tests.

1. If a single line or fitting was the only hydraulic line disconnected, then only the caliper(s) or wheel cylinder(s) affected by that line must be bled. If the master cylinder required bleeding, then all calipers and wheel cylinders must be bled in the proper sequence:
   1. Right rear
      
   2. Left rear
      
   3. Right front
      
   4. Left front
2. Bleed the individual calipers or wheel cylinders as follows:
   1. Place a suitable wrench over the bleeder screw and attach a clear plastic hose over the screw end. Be sure the hose is seated snugly on the screw or you may be squirted with brake fluid.

Be very careful when bleeding wheel cylinders and brake calipers. The bleeder screws often rust in position and may easily break off if forced. Installing a new bleeder screw will often require removal of the component and may include overhaul or replacement of the wheel cylinder/caliper. To help prevent the possibility of breaking a bleeder screw, spray it with some penetrating oil before attempting to loosen it.

1. Submerge the other end of the tube in a transparent container of clean brake fluid.
   
2. Loosen the bleed screw, then have a friend apply the brake pedal slowly and hold. Tighten the bleed screw to 62 inch lbs. (7 Nm), release the brake pedal and wait 15 seconds. Repeat the sequence (including the 15 second pause) until all air is expelled from the caliper or cylinder.
   
3. Tighten the bleeder screw to 62 inch lbs. (7 Nm) when finished.

1. Check the pedal for a hard feeling with the engine not running. If the pedal is soft, repeat the bleeding procedure until a firm pedal is obtained.
   
2. If the brake warning light is on, depress the brake pedal firmly. If there is no air in the system, the light will go out.
   
3. After bleeding, make sure that a firm pedal is achieved before attempting to move the vehicle.

Hope helps (remember to rate this answer).

one or two things make sure the float in the resivior is not stuck and the wire is pluged up,or make sure you bleed the master cylinder.and also you may have to bleed the brakes as well.hope this helped