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If the master cylinder is replaced, care must be taken to prime the new master cylinder by removing all of the air and completely filling it with brake fluid. The spongy feeling is air that is still in the circuits. You will need to bleed the back brakes as well as the front ones again. The order that you bled them seems correct, but perhaps there remained some air in the main trunk lines.
For the best results 2 people are needed. Start at the further distance wheel cylinder and bleed at least three (3) master cylinder reservoir volumes of fluid (back brakes). Bleed the fluid with use of a piece of tubing attached to the bleed port that is long enough to reach almost to the bottom of a long neck or tall clear jar (clear drink bottle works well). When the bleeding begins, after one or two brake pedal pushes, make sure that the end of the tubing is below the surface of the fluid and keep it under. It best to have a clear bleed line (to observe air). Keep pumping the brake pedal while being careful to not completely empty the master cylinder reservoir (leave 1/4 full always). Repeat the same technique for each wheel cylinder with at least two (2) reservoirs full for front brakes. Partially close the bleed ports when almost finished (at least 5 pedal strokes without exit of any air). Completely close the ports during the down stroke of the brake pedal, with the tubing still attached. Be sure each bleed port is closed snuggly.
Most of the brake fluid can be reused, but not the darker portion at the bottom of the jar.
Take Off Nuts That Hold Master Cylinder To Booster. Pull Master Cylinder Away From Booster--Do Not Damage Lines--Feel With Finger At Rear Of Master Cylinder For Fluid--If Found Replace Master Cylinder And Booster With Total Unit Combo For Better Warranty. DO NOT FOOT BLEED--Pressure Bleed Or Gravity Bleed Only.
Start with bleeding master cylinder, have some one pump pedal 3-6 times while lines at master are tight then loose fittings at master a few sec then snug repump aft each snug untill all bubbles are out you have to do both lines,
Do you mean the brake master cylinder? As long as the fluid is at the full mark, and you have no air in the brake lines, it is fine. A spongy brake pedal and poor braking operation happens when air is in the lines. Air can get into the lines when the fluid in the master cylinder is very low, almost out, or when a brake line is pulled apart (like when replacing calipers). To get the air out, one has to bleed the brakes-starting at the rear tires-the longest run from the master cylinder-and ending at the driver's wheel -nearest the master cylinder. Opening the bleed valve at each wheel in turn and pumping the brakes will force fluid into the lines and push the air out the bleed valve. When done properly, all the air in the brake lines should be expelled, and the brake pedal returns to it's firm pedal and good braking efficiency.
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
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You need to bleed the brakes. Look at the brake assembly there should be a little nub with a bolt at the base of it. It takes two people to bleed a brake and you only do them one at a time. Have someone sit in the truck and when you loosen the bleeder nut (little nub with the bolt) have the other person push the brake pedal to the floor. Repeat until no more air bubbles come out. Do this to all of the brakes individually. It is safe to reuse the fluid. Don't let the brake fluid level fall to low or more air will be sucked into the lines.
You have to replace the master cylinder because the fluid that leaks from it is getting into the brake booster and compromising the seals. So you can probably get away with the booster and cylinder. Unless the ABS unit is a part of the either of the affected parts, or isn't working properly, you can leave it alone.--------------------- A fluid-distribution system includes a plurality of fluid-distribution nodes with three-way ports attached to bleed/flush lines and alternate ports attached to vacuum lines. A first pump is used to draw new brake fluid from a new fluid container, push it through the manifold and ports, and through the bleed/flush lines. Fluid flow through the ports is selectively controlled by a computing device. In this manner, a vehicle's brake system including individual brake lines and ABS systems, may be flushed in a prescribed sequence. The vacuum lines are connected to a second pump via alternate ports of the sequential control valve manifold and may be used evacuated air and contaminated brake fluid from the vehicle's bleeder valves or master cylinder. Additionally, the bleed/flush lines may be connected to the alternate ports during priming or purging of the system. This also facilitates storage of the bleed lines as it prevents brake fluid from spilling and prevents air from entering the system.
You need to make sure you have an assistant. The assistant keep adding fluid and pumping the brakes while you operate the bleeder screws.
The procedure--LF,RF,LR,RR (left front, right front,etc). You are moving from the shortest brake line closest to the master cylinder to the longest brake line furthest from the master cylinder. Use an aquarium air hose (12 inch length), and a clear jar to catch the brake fluid. When no more bubbles escape through the hose, the caliper or cylinder is properly bled.
If the level drops below the LOW mark, air may reenter the system. Keep the reservoir full by checking after each bleed!