I took off the ABS unit cover at bottom and then unscrewed the gear plate and removed it for access to the two master cylinder connector bolts.
The ABS gears turned by themself when pulling off the plate.
I installed the new master cylinder, and reservoir, filled with fluid, and stroked the cylinder to cycle out air with bleeder tubes and got fluid through the rear brake line port. After finishing reassembly I installed the whole unit on vehicle, plugged in the ABS electrical connectors and turned on ignition and pumped slowly to bleed the ABS unit's 2 ports. The front brakes bleed well by each wheel but nothing out rear brakes. I am not able to get any pressure to come out the rear brake lines at the unit.
The most common bleeding procedure is to bleed the ABS brake furthest from the master cylinder first, then bleed the other brake that shares the same hydraulic circuit (which may be the other rear brake on a rear-wheel drive car, or the opposite front brake on a front-wheel drive car or minivan). After these have been bled, you then bleed the other brake circuit starting with the furthest brake from the master cylinder.
Air can be very difficult to remove from an ABS modulator assembly because of all the nooks and crannies inside the unit. The modulator may have eight to 10, or more, ABS/traction control solenoid
valves, plus various check valves and dead-end ports. Some ABS modulators have special bleed screws to help you vent the trapped air when bleeding the system. Others do not and require the use of a scan tool to cycle the ABS solenoids while you bleed the system. 1. To bleed the isolation valves in the modulator, there are two bleeder screws. Start with the one toward the engine. Turn the ignition on and apply light pressure on the brake pedal. Open the bleeder screw and allow the fluid to flow until clear. Close the screw and do the same at the second bleeder screw. 2. Depressurize the accumulator by pumping the pedal 40 times with the key off. Wait about two minutes for the brake fluid to de-aerate, then refill the fluid reservoir with DOT 3 brake fluid. 3. Now you can bleed the boost section. This is done by applying moderate pressure on the brake pedal and turning the ignition on for three seconds, then off. Repeat this a total of 10 times. Make sure the pedal feels firm when you have finished, and give the car a road test to make sure the brakes are working properly.
I had the same problem, no brake pressure, with my '94 Cavalier, except I had no pressure at ~any~ of the 4 corners! I jotted down the highlites of Rob Sinpasits' post, 2 hours later?! I had working brakes 4 ****'s.
Although I didn't understand the "apply moderate pressure to brake pedal, turn key on for 3 seconds & turn the key off part, I did it anyways.
After doin' some thinking on this issue, my common sense kicked in. Logic dictates that the ABS reservoir, the aluminum piece attatched to the master cylinder, ~must be~ chocked full of brake fluid & free of air BEFORE any brake fluid will go to the wheel cylinders/caliper's.
Simply put, follow the directions above, you'll have some ~OUTSTANDING~ brakes! Thanks!!
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i have the same problem.. no fluid pressure on my rear brakes. on 1997 cavalier..
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