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Before you install a new master cylinder you are supposed to bench bleed it to get all the air out first then install it the bleed the wheel cylinders the farthest from the cylinder fit so it s like this /1\RR/2\LR/3\RF/4\LF IF YOU DIDN'T BENCH BLEED IT YOU MOST LIKELY BLEW THE PRIMARY SEALS IN IT BUT YOU CAN TRY TO BENCH BLEED IT TO SEE IF IT RESPONDS AND GETS VERY STIFF WHEN YOU APPLY FORCE TO THE PISTON TO PUSH IT IN WITH A BLEEDER KIT INSTALLED ////FITTINGS FOR THE CYLINDER WITH HOSES YOU SUBMERGE INTO THE BRAKE FLUID IN THE CYLINDERS FRONT AND BACK AT THE SAME TIME HELD LIGHTLY IN A VISE TO HOLD IT STEADY
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
I was taught to bench bleed master cylinders as an apprentice but I haven't used it in 40 years. I find it unnecessarily messy and wasteful and distinctly unhelpful. The only thing it has some use for is testing a master cylinder that has just been rebuilt.
I fit the master cylinder dry and connect the pipes regardless of how many ports it has. At this stage my colleague prefers to use a vacuum bleeder but I use an assistant to press and hold/release the brake pedal on command as I release and tighten each pipe in turn with lots of cloth to catch the spillage.
Once I am satisfied the master cylinder is pumping effectively I bleed the system at each wheel as usual.
Car manufacturers don't bench bleed master cylinders. They bleed hydraulic systems by gravity and that is still the best way to fill a system in the repair shop.
first did you perform a bench bleed on the master cylinder? if not bench bleed the master cylinder. had a neighbor with a similar problem with a ford truck. did some reaserch and found the ABS system needed to be bled. one way to bleed air out of it is to connect the diagnostic computer and perform an ABS bleed and then bleed the brakes like you normaly would. The other way was to take the vehicle somewhere you can slide around safely and slam on the brakes causing the ABS to activate. do this a few times and then perform the normal bleed method.
You definitely have to bench bleed the master cylinder, and once you have replaced it in the vehicle, you will need to bleed the brakes from the calipers to remove any additional air.
THE ABS LIGHT IS ON BECAUSE THE MASTER CYLINDER HAS FAILED, IF U DECIDE TO REPLACE THE MASTER YOURSELF BENCH BLEED THE CYLINDER BEFORE U INSTALL IT, IT WILL COME WITH ADAPTERS AND INSTRUCTIONS FOR BENCH BLEEDING, IF U DON'T DO THIS AND AIR GETS INTO THE ABS CONTROL VALVES THEN A TRIP TO THE DEALER WILL BE REQUIRED TO BLEED THE BRAKES PROPERLY.
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