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Brake fluid is expelled from the top cover of master cylinder when brake pedal is depressed why?

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  • GMC Master
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Brake fluid from the Master Cylinder leaks if the Master Cylinder is leaking itself otherwise the leak is somewhere else, have some one check this out, it could be anywhere and you should have seen some drops on the floor by now.

Sounds like a "stuck" caliper piston. Many Chrysler products (by example) used "phenolic" pistons in the calipers which were notorious for seizing in the caliper. Replacement pistons are usually made of steel. With the piston seized heat builds up and ruins the seals in the caliper.

You could have a blown master cylinder that is leaking from the back and into the booster area. Take the cylinder loose from the booster and see if there is fluid in that cavity. Sounds like a massive leak. Look at the rubber hoses and metal lines. The reason you cannot pump up the brakes is because the leak is allowing air to re-enter the system so that pressure cannot build up.

Also, this article could help to check it: how-to-fix-a-brake-fluid-leak

I hope helps (remember to rate and comment this).

Posted on Oct 03, 2010

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3 Answers

What could be the problem? I replace my master cylinder now my brakes drag after driving it a few miles


A few things to check, Is the brake fluid returning to the master cylinder at rest ?, To test jack up one wheel, is it hard to turn, if so slacken off the bleeder screw fluid should be expelled, did the wheel free up, if so the fault is at the master cylinder, check the rod from the pedal to the master cylinder has free play, if not adjust it, if ok there is a fault with the master cylinder buckets swollen or return port blocked. If no fluid was expelled and the wheel is still binding check for frozen wheel cylinder pistons.

Jul 10, 2015 | Cars & Trucks

1 Answer

Air in the fluid master cylinder


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.

Jul 10, 2012 | 1993 Toyota Supra

1 Answer

How do you bleed the brake system on 2003 suzki grand yitara 4x4 with abs brakes


The hydraulic brake system must be bled any time one of the brake lines is disconnected or air enters the system. There are two ways to bleed the system; pressure bleeding or manual bleeding. Both procedures will be given here, although pressure bleeding requires the use of some fairly expensive equipment (a pressure tank) and is seldom used. Both methods are equally effective.The correct bleeding sequence is: left front, right front, left rear, and right rear. On master cylinders equipped with a bleeder valve, bleed the master cylinder last.
PRESSURE BLEEDING
  1. Clean the top of the master cylinder, remove the cover, and attach the pressure bleeding adapter.
  2. The spring-loaded plunger on the front of the proportioning valve must be depressed while bleeding. Wire or tape can be wrapped around the valve to hold the plunger in.
  3. Check the pressure bleeder reservoir for correct pressure 20-29 psi (137-206 kPa) and fluid level, then open the release valve.
  4. Fasten a bleeder hose to the wheel cylinder or caliper bleeder nipple and submerge the free end of the hose in a transparent receptacle. The receptacle should contain enough brake fluid to cover the open end of the hose.
  5. Open the wheel cylinder or caliper bleeder nipple and allow the fluid to flow until all bubbles disappear and an uncontaminated flow exists.
  6. Close the nipple, remove the bleeder hose and repeat the procedure on the other wheel cylinders according to the sequence.


MANUAL BLEEDING(see Figures 1, 2 and 3)An alternative to the pressure method of bleeding requires two people to perform; one to depress the brake pedal and the other to open the bleeder nipples.
  1. Clean the top of the master cylinder, and then remove the cover and fill the reservoir with clean brake fluid.
  2. To prevent squirting fluid replace the cover.
  3. The spring-loaded plunger on the front of the proportioning valve must be depressed while bleeding. Wire or tape can be wrapped around the valve to hold the plunger in.
  4. Install a box end wrench on the left front bleeder screw.
  5. Attach a length of small diameter, clear vinyl tubing to the bleeder screw. Submerge the other end of the rubber tubing in a glass jar partially filled with clean brake fluid. Make sure the rubber tube fits on the bleeder screw snugly or you may be squirted with brake fluid when the bleeder screw is opened.
  6. Have your friend slowly depress the brake pedal. As this is done, open the bleeder screw half a turn and allow the fluid to run through the tube. Close the bleeder screw, then return the brake pedal to its fully released position.
  7. Repeat this procedure until no bubbles appear in the jar. Refill the master cylinder.
  8. Frequently check the master cylinder level during this procedure. If the reservoir runs dry, air will enter the system and the bleeding will have to be repeated.

Hope helps.

Sep 29, 2011 | 2000 Suzuki Grand Vitara

2 Answers

I have a 2004 Land cruiser and changed the right rear brake cyl and brake shoes . What is the proper procedure to bleed the rear brake system. Thank you for your help.


  1. Check the fluid level in the reservoir after bleeding each wheel. Add DOT3 fluid, if necessary.
  2. If the master cylinder was disassembled or if the reservoir becomes empty, bleed the air from the master cylinder as follows:
    1. Disconnect the brake lines from the master cylinder.
    2. Slowly depress the brake pedal and hold it.
    3. Block off the outlet plug with your finger, and release the brake pedal.
    4. Repeat 3 or 4 times.

  3. Bleed the brake starting with the one furthest from the reservoir and then the next furthest, etc.
  4. Depress the brake pedal several times, then loosen the bleeder plug with the pedal held down.
  5. At the point when fluid stops coming out, tighten the bleeder plug to 11 Nm (8 ft. lbs.), then release the brake pedal.
  6. Repeat until all the air in the fluid has been bled out.
  7. Repeat the procedure to bleed the air out of brake line for each wheel.
  8. Check the fluid level and add DOT3 fluid if necessary.

Aug 07, 2011 | 2004 Toyota Land Cruiser

1 Answer

Need to know procedure for bleeding brakes on1987 gmc s15 2.8 litre 4x4 front disc w/abs


MANUAL BLEEDING

For those of us who are not fortunate enough to have access to a power bleeding tool, the manual brake bleeding procedure will quite adequately remove air from the hydraulic system. The major difference between the pressure and manual bleeding procedures is that the manual method takes more time and will require help from an assistant. One person must depress the brake pedal, while another opens and closes the bleeder screws.

In addition to a length of clear neoprene bleeder hose, bleeder wrenches and a clear bleeder bottle (old plastic jar or drink bottle will suffice), bleeding late-model ABS systems may also require the use of one or more relatively inexpensive combination valve pressure bleeding tools (which are used to depress one or more valves in order to allow component/system bleeding). To fully bleed the late model ABS systems, a scan tool should also be used to run the system through functional tests.
  1. Clean the top of the master cylinder, remove the cover and fill the reservoirs with clean fluid. To prevent squirting fluid, and possibly damaging painted surfaces, install the cover during the procedure, but be sure to frequently check and top off the reservoirs with fresh fluid.
CAUTION Never reuse brake fluid which has been bled from the system.
  1. The master cylinder must be bled first if it is suspected to contain air. If the master cylinder was removed and bench bled before installation it must still be bled, but it should take less time and effort. Bleed the master cylinder as follows:
    1. Position a container under the master cylinder to catch the brake fluid.
WARNING Do not allow brake fluid to spill on or come in contact with the vehicle's finish as it will remove the paint. In case of a spill, immediately flush the area with water.
    1. Loosen the front brake line at the master cylinder and allow the fluid to flow from the front port.
    2. Have a friend depress the brake pedal slowly and hold (air and/or fluid should be expelled from the loose fitting). Tighten the line, then release the brake pedal and wait 15 seconds. Loosen the fitting and repeat until all air is removed from the master cylinder bore.
    3. When finished, tighten the line fitting to 20 ft. lbs. (5 Nm).
    4. Repeat the sequence at the master cylinder rear pipe fitting.
During the bleeding procedure, make sure your assistant does NOT release the brake pedal while a fitting is loosened or while a bleeder screw is opening. Air will be drawn back into the system.
  1. Check and refill the master cylinder reservoir.
Remember, if the reservoir is allowed to empty of fluid during the procedure, air will be drawn into the system and the bleeding procedure must be restarted at the master cylinder assembly.
  1. On late model ABS equipped vehicles, perform the special ABS procedures as described later in this section. On 4 wheel ABS systems the Brake Pressure Modulator Valve (BPMV) must be bled (if it has been replaced or if it is suspected to contain air) and on most Rear Wheel Anti-Lock (RWAL) systems the combination valve must be held open. In both cases, special combination valve depressor tools should be used during bleeding and a scan tool must be used for ABS function tests.
  1. 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:
    1. Right rear
    2. Left rear
    3. Right front
    4. Left front
  2. Bleed the individual calipers or wheel cylinders as follows:
    1. Place a suitable wrench over the bleeder screw and attach a clear plastic hose over the screw end. Be sure the hose is seated snugly on the screw or you may be squirted with brake fluid.
Be very careful when bleeding wheel cylinders and brake calipers. The bleeder screws often rust in position and may easily break off if forced. Installing a new bleeder screw will often require removal of the component and may include overhaul or replacement of the wheel cylinder/caliper. To help prevent the possibility of breaking a bleeder screw, spray it with some penetrating oil before attempting to loosen it.
    1. Submerge the other end of the tube in a transparent container of clean brake fluid.
    2. Loosen the bleed screw, then have a friend apply the brake pedal slowly and hold. Tighten the bleed screw to 62 inch lbs. (7 Nm), release the brake pedal and wait 15 seconds. Repeat the sequence (including the 15 second pause) until all air is expelled from the caliper or cylinder.
    3. Tighten the bleeder screw to 62 inch lbs. (7 Nm) when finished.
  1. 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 obtained.
  2. If the brake warning light is on, depress the brake pedal firmly. If there is no air in the system, the light will go out.
  3. After bleeding, make sure that a firm pedal is achieved before attempting to move the vehicle.

Hope helps (remember to rate this answer).

Apr 13, 2011 | 1987 GMC Jimmy

1 Answer

I replaced the whole back break line,as i try to bleed them i get fluid out of the front passenger side and the back driver side,but nothing out of the other two.whats the problem?


Hi, your proportioning valve is stuck. Take the caps off and recenter the one stuck valve. Then rebleed the system using the procedure below. Thanks for using fixya.

jturcotte_1047.gif
For those of us who are not fortunate enough to have access to a power bleeding tool, the manual brake bleeding procedure will quite adequately remove air from the hydraulic system. The major difference between the pressure and manual bleeding procedures is that the manual method takes more time and will require help from an assistant. One person must depress the brake pedal, while another opens and closes the bleeder screws.
  1. Deplete the vacuum reserve by applying the brakes several times with the ignition OFF .
  2. Clean the top of the master cylinder, remove the cover and fill the reservoirs with clean fluid.
  3. The master cylinder must be bled first if it is suspected to contain air. If the master cylinder was removed and bench bled before installation it must still be bled, but it should take less time and effort. Bleed the master cylinder as follows:
    1. Position a container under the master cylinder to catch the brake fluid.
    2. Loosen the front brake line(s) at the master cylinder and allow the fluid to flow from the front port.




WARNING Do not allow brake fluid to spill on or come in contact with the vehicle's finish as it will remove the paint. In case of a spill, immediately flush the area with water.

  1. Tighten the line connection(s).
  2. Have an assistant depress and hold the brake pedal.
  3. Loosen the line connection(s) again, allowing air to escape from the master cylinder.
  4. Tighten the line(s), then have the assistant release the brake pedal and wait for 15 seconds.
  5. Repeat steps D through F until the line(s) are free of air.
  6. When finished bleeding the air from the master cylinder, tighten the line connections to 20 ft. lbs. (27 Nm).
  7. Repeat steps B through H, only with the master cylinder rear pipe fitting(s).

  1. Refill the master cylinder with fresh brake fluid.



WARNING Never reuse brake fluid that has been bled from the system.

  1. 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:
    1. Right rear
    2. Left rear
    3. Right front
    4. Left front

  2. Bleed the individual calipers or wheel cylinders as follows:
    1. Place a suitable wrench over the bleeder screw and attach a clear plastic hose over the screw end. Be sure the hose is seated snugly on the screw or you may be squirted with brake fluid.
    2. Submerge the other end of the tube in a transparent container of clean brake fluid.
    3. With the help of an assistant, apply the brake pedal slowly and hold.


During the bleeding procedure, make sure your assistant does NOT release the brake pedal while a fitting is loosened or while a bleeder screw is opening. Air will be drawn back into the system.
  1. While the assistant continues to apply pressure to the brake pedal, loosen the bleeder screw, and watch for air bubbles in the container.

Be very careful when loosening the wheel cylinder and brake caliper bleeding screws. The bleeder screws often rust in position and may easily break off if forced. To help prevent the possibility of breaking a bleeder screw, spray it with some penetrating oil before attempting to loosen it. Installing a new bleeder screw will often require removal of the component and may include overhaul or replacement of the wheel cylinder/caliper.
  1. Tighten the bleeder screw.
  2. Instruct the assistant to release the brake pedal.
  3. Wait approximately 15 seconds, and instruct the assistant to depress the brake pedal again.

Remember, if the reservoir is allowed to empty of fluid during the procedure, air will be drawn into the system and the bleeding procedure must be restarted at the master cylinder assembly.
  1. Repeat steps C through F until there are no air bubbles present in the container.

  1. 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 obtained.
  2. If the brake warning light is on, depress the brake pedal firmly. If there is no air in the system, the light will go out.
  3. Once all the air is bled from the system, install the bleeder screw caps.
  4. After bleeding, make sure that a firm pedal is achieved before attempting to move the vehicle.

Feb 14, 2011 | 1994 Pontiac Grand Am

1 Answer

How to bleed brakes on 1997 Saturn


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.

WARNING Make sure the master cylinder contains clean DOT 3 brake fluid at all times during the procedure.
  1. The master cylinder must be bled first if it is suspected of containing air. Bleed the master cylinder as follows:
    1. Position a container under the master cylinder to catch the brake fluid.
    2. Loosen the left front brake line (front upper port) at the master cylinder and allow the fluid to flow from the front port.
    3. Connect the line and tighten to 24 ft. lbs. (32 Nm).
    4. 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.
    5. Tighten the brake line to 24 ft. lbs. (32 Nm) when finished.
    6. Repeat these steps for the right front brake line (rear upper port) at the master cylinder.
WARNING 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.
  1. 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:
    1. Right rear
    2. Left front
    3. Left rear
    4. Right front
  2. Bleed the individual calipers or wheel cylinders as follows:
    1. Place a suitable wrench over the bleeder screw and attach a clear plastic hose over the screw end.
    2. Submerge the other end in a transparent container of brake fluid.
    3. 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.
    4. 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.
  3. 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 obtained.
zjlimited_349.jpg

Fig. 1: Loosen the front brake line in order to bleed the master cylinder

zjlimited_350.jpg

Fig. 2: Connect a bleed hose from the bleed valve on the front caliper to a jar of brake fluid

zjlimited_351.jpg

Fig. 3: Always follow the lettered sequence when bleeding the hydraulic brake system





Hope this helps to solve it; remember to rate this answer.

Dec 29, 2010 | 1997 Saturn SL

1 Answer

DSC control unit repair kit uncoded part. When i put this on will i have have brakes if air get into line.?.


Think of brake fluid as being a flexible piston. When you push your foot on the brake pedal the fluid is pushed out of the master cylinder and along the pipes and into the wheel cylinders, where it pushes out the pistons and in turn pushes the pads to contact the discs....If air gets into the system, the brakes become spongy and only effective when you pump them, which in fact is compressing the air. You can end up with no brakes at a time when you really need them urgently.
Air will enter whenever the system is opened, and the only way to expel the air is by bleeding.
Begin with the wheel furthest from the master cylinder and move one closer each time, ending with the closest wheel.
Have a good friend sitting inside the car.....and prepare whoever for some exercise....
Someone else should be outside ready to top up the brake fluid reservoir, each time the bleed nipple is opened and then closed....
Take an empty bottle and a tight fitting length of plastic pipe, Pour some fluid into the bottle so the end of the pipe can remain covered at all times. Fit the pipe over the bleed nipple....Shout to your friend inside..."PUMP!"....Then wait for your good friend to do just that.
The pedal should be depressed as far as possible each time and then after four or five pumping actions, shout "DOWN" at which time your good friend should hold the pedal as far down as it will travel...
You in your comfortable place laying under the car, should open the nipple and while the pedal is down close it again....Repeat until all air is expelled....
The pedal will become progressively harder, but must be pushed with force to the floor and remain there without being lifted, at all until the nipple is closed each each time the nipple is opened....
Do this to each wheel in turn and if the pedal still feels spongy when you've finished....you haven't finished....I love this part!.... So begin again!... No really I'm not a sadist....promise I'm not....
Best regards Johngee10
Ps. Don't fall asleep under the car, your friends may become upset with you.

Oct 29, 2010 | 2002 BMW 7 Series

2 Answers

Pedal goes to floor almost. new master cylinber & bled all brakes & master cylinder whuch didnt solve problem. possibly electrical or stuff under master cylinder?


The "pedal goes to floor" is a mechanical problem and it more than likely that there is still air in the system and that the bleeding is not complete. Find level ground and start at the back of the truck with the hand brake off, chock the wheels if needed. Fill the brake fluid reservoir. Loosen the bleed screw on the back brake assembly and have a colleague depress the brake. Tighten and release the brake, NEVER allow the brake pedal to rise when the bleed screw is loose as this will **** air back into the system. Undo the bleed screw about half a turn and again depress the brake, tighten off at bottom of stroke and again release the pedal. Every couple of times top up the brake fluid reservoir. Keep pushing fluid through until about half a pint has been expelled from the bleed screw assembly. Tighten off the bleed screw for good. Go the other rear wheel and repeat the process making sure that the reservoir never runs out of fluid. . Now go to the front and repeat with both wheels. There should come a time that your colleague can report that there is increasing resistance when standing on the brake pedal. If after all this the pedal continues to sink to the floor it sounds like the seal on the master cylinder piston is defective or there is a leak in the brake line.

Apr 24, 2010 | 1994 Chevrolet C1500

2 Answers

I have no pressure in the clutch and changed the master cylinder


you need to bleed master & slave cyl master dont hold much fluid must bleed similar like brks when when starts coming out of bleeder close bleeder let sit couple of minutes air travel top of master pump pedal more repeat pumping pedal air residue will work it self out

Aug 11, 2009 | 1997 Pontiac Grand Am

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