Brakes keep going out replaced master cylinder but not helping?
Brakes keep giving out , replaced master cylinder , bled all brakes and still giving out I have to keep loosening bolts that connect lines to master cylnder to relieve the brake fluid and keep pumping brakes and they will work after I do that but as I drive I can feel the brakes giving out ?
My car has 317000 miles.
My car has an automatic transmission.
Experienced mechanics share their insights in answering this question :
There are two possible vehicle recalls pertaining to the issue are having. The ABS is the cause of most of the problems similar to what you are experiencing. I recommend contacting a dealer with your vehicle VIN number to see if you have active recalls.
How to Identify and Fix Common car Problems ?
Our sources include academic articles, blog posts, and personal essays from experienced mechanics :
The Three Most Common Reasons for a Soft Brake Pedal
The brake master cylinder is leaking internally or externally. There is a leak in the system someplace other than the brake master cylinder. One or more of the calipers has a frozen or rusted moving part that isn`t moving as designed.
The most likely cause of a sinking pedal with no external leakage is a faulty brake master cylinder that`s leaking internally. Were the brakes hot, we might consider boiling fluid due to moisture contamination or friction material gassing.
A worn or malfunctioning master cylinder. If the master cylinder isn`t performing as designed, it may need to be replaced. Defective replacement cylinder. If, after the master cylinder has been replaced and the system has been bled, and still your brake pedal goes to the floor, the new master cylinder may be defective.
It could be that the brakes weren`t lubricated correctly in the service. Or, that new brakes weren`t broken in correctly. The driver may have unintentionally overheated the new brake pads to the point where the brake pads developed a glaze from overheating, which does cause squeaks.
This can be due to a number of problems: a leak in a brake line, a loss of pressure within the master cylinder itself due to a failed seal, or air being introduced into the braking system. Your first reaction to encountering spongy brakes should be to rapidly pump the brake pedal with your foot.
Yes master cylinders can fail without leakage, the clutch master cylinder has a piston inside and there are separate channels for hi-pressure line and return(low pressure) line and their location in the cylinder differs for manufacturers.
Pedal and hold
Hold. Bleed. Repeat. Loud callouts of “pump it up” or “pressure” and “hold it down” can make the garage or driveway sound like a Sunday morning at the Waffle House, but the two-person procedure is a tried and true way to get the brakes bled quickly.
Increased braking distance is a clear sign of bad or failing brake boosters. Warning lights, such as the ABS, or anti-lock braking system, will activate if you have an electronic brake booster system failure. Fluid leakage is typical for hydraulic booster failure.
Brake Booster Check
With the car turned off, pump the brake pedal four or five times until you get a hard brake pedal. Continue to hold the brake pedal down with moderate pressure and start the vehicle. The brake pedal should drop.
This pressure travels from the master cylinder, through the brake line, and acts on the brake caliper and brake rotor. However, if air bubbles are in the brake line, hydraulic pressure is reduced, making your entire braking system less effective and your vehicle more difficult to control.
Worn-Out Master Cylinder
The master cylinder holds the brake fluid to generate hydraulic pressure and sends the pressure to the front and rear brakes to stop the vehicle. A leak in the cylinder seals will reduce the brake fluid pressure resulting in spongy brakes.
After you change your brake/clutch master cylinder kit or replace the master cylinder assembly, you must bleed air/fluid to prevent `trapped air` in the system after installing. There would be an `air pocket` in the line.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
Brakes keep going out replaced master cylinder but not helping?
ANSWER : There are two possible vehicle recalls pertaining to the issue are having. The ABS is the cause of most of the problems similar to what you are experiencing. I recommend contacting a dealer with your vehicle VIN number to see if you have active recalls.
Read Full Q/A … : Brakes keep going out replaced master cylinder but not helping?
I just replaced my brake master cylinder and the brakes still feel soft. What do I need to do after I replace the master cylinder
ANSWER : From what you’ve described you will have to bleed your brakes. Also, I believe you may have a leak in one of the lines. You may want to use a wrench and tighten the lines a little more. If you’re unable to fix this yourself, consider YourMechanic, as one of our mobile technicians can come to your home to bleed your brakes, diagnose the Check Engine Light, and help you make the appropriate repairs to your car.
Read Full Q/A … : Brakes keep going out replaced master cylinder but not helping?
Low brake pedal and anti-lock brakes are not kicking in.
ANSWER : The brake pedal is working to stop the vehicle, but there may be air in the controller unit causing the ABS brakes to not function. I recommend bleeding the brake system from the farthest location from the master cylinder to the master cylinder including the ABS unit. If the brakes are still spongy after a full bleed, then the controller will need to be replaced. If you need further assistance with your brake pedal being spongy, then seek out a professional, such as one from Your Mechanic, to help you.
Read Full Q/A … : Brakes keep going out replaced master cylinder but not helping?
Soft brake pedal after replacing rear brakes and master cylinder 2003 Audi A4
ANSWER : Hello. If you have no pressure to the rear calipers at all and if the master cylinder is new then you may have forces some debris into the ABS unit when you compressed the pistons in the rear calipers. In some cases the system can be pressure bled to fix it but it may need a new ABS unit.
Read Full Q/A … : Brakes keep going out replaced master cylinder but not helping?
Changed brake master cylinder, bled 10 times, and the pedal is soft The rear brakes are not locked but close. Truck now running rough.
ANSWER : You will have to bleed the brakes from the farthest location all the way to the master cylinder. There is still air in the lines causing the issue. Check the vibrations on the vehicle to see if the engine mounts are damaged or if the brakes are not releasing causing the engine to run harder than normal to overcome the braking force. If you need further assistance with your vehicle’s brake system, then seek out a professional, such as one from Your Mechanic, to help you.
Read Full Q/A … : Brakes keep going out replaced master cylinder but not helping?
Replaced master cylinder and brakes still going to the floor and not working. Bed both master cylinders and each wheel.
ANSWER : Hi, thanks for writing in. At first it sounds like you may still have air in the system. The other option is that you may have a leak somewhere. Try to bleed the master cylinder and the lines again. The new master cylinder must be bench bled off of the vehicle exactly as the instructions say. The other problem could be a leak on the system. You should check for drips, puddles forming, or other signs of leaking brake fluid. Worst case scenario, the replacement master cylinder may have come to you faulty in the first place. This is rare but can happen, especially when it comes to remanufactured master cylinders. New ones typically don’t have issues. If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.
Read Full Q/A … : Brakes keep going out replaced master cylinder but not helping?
I replaced the brake light switch. Gear lever unlocked because it had locked. Now the brakes feel hard.
ANSWER : Hi, thanks for writing in. You need to check the brake switch install adjustment. You may have the switch adjusted too tight and it is holding the the brake pedal partly down. This will cause the brake master cylinder to not release the brakes when you let off the pedal. Readjust the switch away from the pedal until you feel some free play again in the pedal. This should fix the problem. If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.
Read Full Q/A … : Brakes keep going out replaced master cylinder but not helping?
EPC light on 2004 Jetta. Code said brake switch faulty, but brakes lights worked. Replaced brake switch, now no brake lights.
ANSWER : Hi there. The first thing that pops in my mind beyond of what you have listed is perhaps the electrical harness attached to the brake switch. Perhaps the harness itself is damaged or you have an exposed wire, loose ground wire somewhere. You might want to have a professional mobile mechanic come to your location and complete a brake lights not working inspection to help you diagnose this issue.
Read Full Q/A … : Brakes keep going out replaced master cylinder but not helping?
