I replaced all the lines on the hcu.i cant' get system to bleed.if you are looking at the hcu i put the 3 lines in the top from left to right startin with master cyl front master cyl rear then rear on the bottom i put right front then left front is this correct?and is there a special bleeding order?
Some vehicle made by GM require special sequence bleeding and a scan tool to open the abs brake module to bleed all the air
SOURCE: back brake lines wont bleed on 77 chevy truck
Check out this link & read about combination valve & how to center it when bleeding.
http://www.autozone.com/addVehicleId,1321403/initialAction,repairGuide/shopping/repairGuide.htm?pageId=0900c1528007a632
SOURCE: cant bleed out brakes
It takes time, do you know the sequence to bleed the brakes? Most cars r different. And you have to keep pouring brake fluid, That is a two person job. Make sure all lines r connected to MC and not leaking. After a while if nothing comes out MC could be diffective.
SOURCE: 1994 Cavalier -replaced master cylinder-no pressure to rear brake
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.
SOURCE: how do you bleed the abs unit on a 1997 chevrolet truck
start by bleeding the master cylinder bleed the line closest to the fire wall, then proceed to the right rear wheel, left rear wheel, right front wheel, and then the left front wheel.
Fig. HCU mounting-Mirage
Fig. HCU mounting-Galant
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