A perssure bleeder is the best way to bleed the brakes. You can't properly just bleed one or two lines. You must start with the left rear, then right rear, then front right and finally front left. Any other order will just push a bubble around.
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A bad master cylinder usually gives a pedal that will gradually drop to the floor after braking, i.e. stopped at a light, the vehicle will start to crawl and you'll have to increase pressure or pump the brake. Sounds like the problem is not being caused by the master cylinder but by the calipers. The caliper pistons and master cylinder piston MUST operate as a matched set for volume of fluid displacement.
Are you certain the calipers are an exact match for the vehicle, i.e. the master cylinder used in your Avy??? Do a couple of quick pumps bring up the pedal and it remains firm under pressure?
If the volume of brake fluid displacement for the new caliper pistons to expand exceeds that of the old calipers, the pedal will go lower because you only get one stroke of a given volume displacement from the master cylinder's in line pistons no matter how much fluid is in the reservoir...a larger volume of the caliper pistons will lower the pedal, too much and the pedal will hit the floor....if so, either go back to calipers with piston displacement similar to the old volume or get a master cylinder with a larger bore piston so the displacement matches that of the calipers pistons.......
Replaced and added to my original post:
If your brake specialist agrees that the above is causing the problem, and you decide to replace the master cylinder rather than going back to the old calipers, you will also have to make certain that the proportioning valve assembly is compatible with the new arrangement.
You must start bleeding the brakes at the wheel farthest from the master cylinder (usually the right rear), then the next farthest from the master cylinder, then the next, then the closest. If your master cylinder is at the left front of the car, start with the right rear, then the left rear, then the right front, then the left front. If you don't bleed the brakes in the correct order, you are just shifting the air in the lines from one line to another. Make sure that you close the bleeder before letting the brake pedal up, and the engine should not be running when you bleed the brakes... Make sure that the emergency brake is off. Make sure that the master cylinder does not run out of brake fluid at any time that you are bleeding the brakes.
this is best way i know is to fill resevoire with fluid open all bleeders up let it start dripping out of them keeping fluid full in resivoire do this until bleeders leaking real good then shut all bleeders put cap on master cylinder crank car check feel of brakes now if pedal still soft then bleed brakes with car not running check again with car running still soft bleed again with car running
The brake system bleeding procedure differs for ABS and non-ABS
vehicles. The following procedure pertains only to non-ABS vehicles. For
details on bleeding ABS equipped vehicles, refer to the ABS procedures
later in this section.
Make sure the master cylinder contains clean DOT 3 brake fluid at all times during the procedure.
The master cylinder must be bled first if it is suspected of containing air. Bleed the master cylinder as follows:
Position a container under the master cylinder to catch the brake fluid.
Loosen the left front brake line (front upper port) at the master cylinder and allow the fluid to flow from the front port.
Connect the line and tighten to 24 ft. lbs. (32 Nm).
Have an assistant depress the brake pedal slowly one time and hold
it down, while you loosen the front line to expel air from the master
cylinder. Tighten the line, then release the brake pedal. Repeat until
all air is removed from the master cylinder.
Tighten the brake line to 24 ft. lbs. (32 Nm) when finished.
Repeat these steps for the right front brake line (rear upper port) at the master cylinder.
Do not allow brake fluid to spill on or come in contact with the
vehicle' finish, as it will remove the paint. In case of a spill,
immediately flush the area with water.
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:
Bleed the individual calipers or wheel cylinders as follows:
Place a suitable wrench over the bleeder screw and attach a clear plastic hose over the screw end.
Submerge the other end in a transparent container of brake fluid.
Loosen the bleed screw, then have an assistant apply the brake
pedal slowly and hold it down. Close the bleed screw, then release the
brake pedal. Repeat the sequence until all air is expelled from the
caliper or cylinder.
When finished, tighten the bleed screw to 97 inch lbs. (11 Nm) for the front, or 66 inch lbs. (7.5 Nm) for the rear.
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
Fig. 1: Loosen the front brake line in order to bleed the master cylinder
Fig. 2: Connect a bleed hose from the bleed valve on the front caliper to a jar of brake fluid
Fig. 3: Always follow the lettered sequence when bleeding the hydraulic brake system
Hope this helps to solve it; remember to rate this answer.
hi from the uk have had this problem on a customers car b4 who had replaced frot calipers and pads and pedal went to floor on inspection of caliper i found that the steel spring clip that fits into two holes in the front face of caliper and must also locate behind the caliper carrierbehind two lugs was fitted incorrectly it had been fitted behind the outer pad resulting in when brake pedal off ?the caliper being floating type as it is known because it is fixed by two screw pins/bolts and moves on these pins/bolts as pads wear ? what happens is the spring fitted wrongly ? actually pushes against the outer pad and as a result the caliper piston is pushed back into its cylinder slightly as it moves on the locating pins/bolts resulting in pedal going to floor on 1st application but if pumped ? some brake pedal force is felt but is lost again when pedal released ? so try this ? remove the steel clips from both front calipers that retain caliper to carriers then press brake/pump pedal ? if as suggested above works? your pedal should pump up and remain ok when you release and still be firm when re applied ? all above is what i found on ford ford but many other models use similar calipers and spring locating recheck how this spring should locate hope this helps ? good luck
No it is not that big of a deal. It is normally 2-3 nuts and your brake lines. The things to make sure of is that brake fluid does not get on any of the electronics below the cylinder by using a towel. Also make sure to bleed the cylinder before hooking the brake lines in all the way. Basically you can do this by screwing in the brake lines about half way and hitting the brake pedal about half way down. Make sure the reservoir does not get empty. Bleed it until there is nothing but fluid coming out of both lines. Obviously this is best done with two people. Have them hold the pedal down while you tighten the lines fully and you should be good.
MAKE SURE THE ARE NO OTHER LEAKS.IF U DID NOT BENCH BLEED THE MASTER CYLINDER BEFORE U PUT IT ON U PROBLEBLY HAVE AIR IN THE SYSTEM.BLEED THE MASTER CYLINDER AT THE LINES THAT COME OFF OF IT.THEN U NEED TO BLEED THE REAT OF THE BRAKES IN THIS ORDER.RIGHT REAR,LEFT FRONT,LEFT REAR.RIGHT FRONT.WHEN BLEEDING THE BRAKES WAIT 15 SECONDS BETWEEN PUMPS OF THE BRAKE PEDAL.IF U GO TO FAST U CAN DAMAGE THE MASTER CYLINDER.GOOD LUCK
I am a hydraulic technician and I can tell you that air is a killer in the hydraulic system.
Start from the rear and work your way forward. I f you are using the two person method, make sure the second person keeps the master cylinder full. If the fluid level dropped anywhere in between pressing and releasing the brakes....you have a lot of air in the system.
Make sure you are tightening the bleed valve when the brake pedal is full pressed.
Remeber...start from the rear brakes first, then do the front.