No brakes

I am working on the brakes, the pedal is going to the floor. We have replaced the master and the rrear wheel cyclinder and bleed the system. We have good fluid flow to all the wheels, but still nothing.
My car has an automatic transmission.
Experienced mechanics share their insights in answering this question :
If the brake pedal is going to the floor even after replacing master cylinder and rear brakes you still have air in the brakes. You may need to use a pressure bleeder to push fluid through the system and bleed out air. If vehicle is equipped with anti lock brakes then you will need to put it into bleed function using a scanner so air can be bled out of it. Make sure you bench bled air out of master cylinder or you may not be able to get the air out of it due to angle it is at.

How to Identify and Fix Common car Problems ?

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Air in the brake line(s) is the most common cause of a soft/spongy brake pedal. If air gets into the brake lines, it can prevent brake fluid from flowing properly, causing the brake pedal to feel spongy or soft. If the brakes are soft or spongy, this is a good time to change or flush the brake fluid.
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.
When brakes are not as responsive as what they should be, or if the brake pedal “sinks” down to the floor, this is a possible indication of a braking system leak. It could be a brake fluid leak, or a brake hose air leak.
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.
When your ABS system malfunctions are can also cause a spongy brake pedal. Your ABS system is designed to allow the driver to maintain more control of the car in a high-speed stop.
Common signs of a faulty vacuum brake booster check valve include the brake pedal being difficult to engage, feeling spongy, or not working at all.
A spongy brake lever, or a brake lever which has to be pulled a long way before you feel the brake start to work, is a sure sign of air trapped in the brake system. Some brakes can be more troublesome to bleed than others. Even after multiple bleeds air can remain trapped inside the caliper.
If the brake pedal sinks to the floor when the engine is running then there may be a problem with the brake booster.
Usually, your brake pedal will sink if the ABS or master cylinder cannot maintain the proper hydraulic pressure. This inability to maintain hydraulic pressure will not only make your brake pedal sink to the floor, but it will also make it much more difficult to stop your automobile.
In the Car: With the brake system bled, pump the brakes a few times and hold. The brake pedal should be firm. If the brake pedal is spongy, this could indicate air remaining in the lines or a mechanical problem, such as a sticking brake caliper slider.
These could be some reasons you have no brake pressure after bleeding your brakes: Air in the brake lines. Brake fluid leak somewhere in the system (check your fluid level to make sure it`s remained at the right amount) Faulty seal in the master cylinder.
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. If this brake pedal remains hard, there is a problem with the brake booster, such as a ripped diaphragm.
On the contrary, you`re not supposed to pump air brakes. Everytime you release the brake, you release pressure in the air system. If your pressure drops too low but not low enough for the emergency brake to activate, you`re not going to stop.
On the air-brake system the driver must pump or use stab braking in an emergency. If the anti-lock brake system fails or malfunctions, the driver must resort to stopping the vehicle by using the normal air-brake method.
Brake pulsation usually only has one cause, which is warped rotors/brake discs. The main cause of warped rotors is excessive hard braking or fast stops which can severely overheat the discs.
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.
Driving a vehicle with spongy brakes is not recommended as they compromise your car`s braking ability on the road. If you have spongy brakes, you should avoid driving the car until the braking system issue gets resolved.
The most common cause of failure is a leak in the brake lines. The brake fluid will slowly drain out, until there isn`t enough left to transmit the pressure from the pedal to the tires. The brakes can also fail when the discs or drums wear out, so they can no longer put enough friction on the wheels to stop them.
The most common cause of failure is a leak in the brake lines. The brake fluid will slowly drain out, until there isn`t enough left to transmit the pressure from the pedal to the tires. The brakes can also fail when the discs or drums wear out, so they can no longer put enough friction on the wheels to stop them.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

When I put my foot on the brake my back left brake light goes off, when I take it off the brake the brake light comes on
ANSWER : I would suggest trying to disconnect and reconnect the wiring to the rear lights. I have seen these older Toyota vehicles rear lighting short out on the lights themselves due to the way the light circuit was made on the lamp housing. Look at the housing circuit on the light to see if one is touching another, and that could tell you why it is malfunctioning. There could also be a problem with the brake light switch. If you are not comfortable dealing with wires, I recommend getting in touch with a certified mechanic who can look at your brake light issue for you to see what’s going on.

Read Full Q/A … : No brakes

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 … : No brakes

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.

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Supportive bar attached to brake pedal interrupts proper braking process
ANSWER : It’s possible to have someone alter the brake pedal or adapt a brake pedal from a different vehicle. You may call around to some customization shops to see if anyone is interested in taking on the project. But first, I would try reaching out to the selling dealer with your concern – especially since it is a new model. Good luck.

Read Full Q/A … : No brakes

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.

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Brake sensor is to sensitive causing brakes to flicker while driving. 2005 Mercury Montego
ANSWER : Hi there – your brake light switch needs a minor adjustment. It is adjusted too "tight" or close to the brake pedal lever, or possibly has failed. Adjusting/replacing it will eliminate this flickering problem. I recommend a brake light isn’t working inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.

Read Full Q/A … : No brakes

Hard brake pedal and rear brakes locking up.
ANSWER : Hi. I will help you with this issue you are having with your 2001 Durango. Unless you bled the master cylinder, it is possible there is still air in the system. If you car is equipped with ABS, air could have also gotten trapped in the ABS modulator. If ABS equipped, a bi-directional scan tool would be essential to manually activate the ABS system to clear air from that segment of the lines while you are bleeding the system. It is also possible that in all of this work somehow the proportioning valve has been affected causing the desired pressure differential, front versus back, to get out of spec. Using a 2,500 PSI gauge, you can check the pressures at each wheel and that will definitely give you a clue as to which brake circuit is the issue (or both), whether the proportioning valve is working properly and whether the line pressures at each wheel are within spec. Should you need a second opinion, by all means feel free to contact YourMechanic for assistance and we will diagnose and repair the issue for you.

Read Full Q/A … : No brakes

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 … : No brakes