Hard brake pedal and rear brakes locking up.
I had an issue with a spongy pedal so I replaced my rear wheel cylinders as it felt like my back brakes were grabby. I got the new ones on and had absolutely no brake pedal. Trying to fix the problem I put a new master cylinder, brake booster, a brake line I found was leaking, a booster check valve and bled the brakes a whole bunch of times. My pedal is now hard and it seems like the front brakes aren't doing anything and the rear brakes want to lock up unless you barely tap the pedal. I've since dropped it off at the dealership but would like to know some possible causes of the proble
Experienced mechanics share their insights in answering this question :
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.
How to Identify and Fix Common car Problems ?
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In most cases, stiff brakes are caused by problems with the brake booster. Brake boosters multiply the force applied to your brake pedal, and they work in tandem with the hydraulic fluid in the brake lines. This system, also known as power brakes, allows you to stop a two-ton vehicle with just your foot!
One of the most common causes of one or two wheel lockup on drum brake equipped vehicles is the service and/or parking brake adjustment. If either one or both of these adjustments are done incorrectly it can result in the rear brakes being very sensitive.
Vacuum – or really lack of vacuum pressure – is the most common cause of a hard brake pedal, and therefore the first thing to look at when a hard pedal is present. Any brake booster (whether from Master Power or any other supplier) needs a vacuum source to operate.
A malfunctioning Anti-lock Braking System (ABS) can also cause a hard brake pedal. The ABS system is responsible for preventing the wheels from locking up during emergency braking. If the ABS system malfunctions, it may cause a loss of hydraulic pressure, resulting in a hard brake pedal.
Common Reasons Brake Lock Up
Overheated braking system. Using the wrong brake fluid. Damaged or broken parts (calipers, brake pads, pistons, rotors, or others) Defective ABS components.
The likely cause is a failed wheel bearing unless something exceptional has caused the brake caliper to lock the brake rotor. By far, the most common cause of what you are describing is simply bearing failure though. Repair can be obtained by requesting wheel bearing replacement.
The most common causes of your brakes not releasing is a seized caliper or brake pad. This typically occurs due to rusting or ageing. Typically, you will notice your vehicle pulling to one side when you press down on your brakes.
There could be a problem with the master cylinder. When you push down on the brake pedal, the fluid pressure should be able to get to the brake pads or drum shoes. If the master cylinder valves and seals are not properly in place, the brakes may lock up.
The cup seals or the cylinder bore may be worn. Any time that the brake pedal of a vehicle is fading towards the floor, internal leaking or cup seals being bypassed must be considered. A fading pedal that has no external leak is one of the most common master cylinder symptoms caused by the cup seals.
The ABS modulator is the hydraulic assembly in vehicles that use the anti-lock braking system (ABS) to optimize the brake pressure. A damaged modulator may lead to malfunctioning of the brake valve resulting in spongy brakes.
ABS hydraulic assembly malfunction
An internal failure, corrosion or debris in the brake fluid can cause a valve not to operate properly, resulting in a low or spongy pedal. Important note: If you experience a spongy/soft or low brake pedal, have your vehicle inspected immediately by your mechanic.
When it is functioning correctly the ABS system is designed specifically to prevent the wheels from locking up during heavy braking, preventing loss of traction. However, there can be certain instances where a faulty ABS module can behave erratically, causing your brakes to lock up even under normal driving conditions.
Non-ABS and ABS: A low brake fluid level, using the incorrect brake fluid, or brake friction material saturated with brake fluid from a leaking component can cause brake lock-up.
An anti-lock braking system (ABS) is a safety feature that prevents wheels from locking to avoid skidding or to retain more control while skidding. Without ABS, vehicles could potentially overturn.
If your wheel bearing fails, it can cause the wheel to stop while you are driving or possibly even to fall off. At the very least, before a wheel falls off, a failed wheel bearing can/will cause significant damage to your vehicle, so it`s very important to keep an eye on these and keep them maintained.
A bad wheel cylinder is often hard to spot because it`s inside the drum brake. However, here are some signs that something`s wrong with it: Your car has poor brake response — you`ll find that braking takes longer. Your brake pedal feels mushy, soft, or the pedal sinks to the vehicle floor.
What are the symptoms of a bad brake pedal position sensor? Commonly, your brake lights won`t activate or they will stick on all the time. Your cruise control might not function, and it`s possible you could have trouble moving the gearshift lever.
The easiest way to diagnose this problem is to pump the brake pedal gently a few times. In doing so, the pedal should become firmer with each gentle press of the pedal. If it does, then the necessary answer is bleeding the brakes.
Typically, a vacuum leak will cause situations like hard starting, rough idle, excessive fuel consumption, and engine codes. You might even be able to hear a leak – sometimes a whooshing or whistling sound can be heard with the engine running.
The vacuum sensor (or pressure sensor) is an important part of the brake boosters in modern cars. Its purpose is to monitor the amount of vacuum present in the brake booster, sending a message to your car`s onboard computer when more vacuum pressure is needed.
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.
Unresponsive brakes or the `brake pedal goes to floor` symptom is a possible indication of a leak in your braking system. With a leak, an incorrect amount of hydraulic fluid will flow through your brake system— hindering your braking ability. A brake system leak could stem from many sources.
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.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
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 … : Hard brake pedal and rear brakes locking up.
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 … : Hard brake pedal and rear brakes locking up.
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 … : Hard brake pedal and rear brakes locking up.
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 … : Hard brake pedal and rear brakes locking up.
Rear brakes not grabbing – 1995 GMC K2500
ANSWER : Hello. It is not in the ABS, but may be the proportional valve not giving the correct pressure split front to the rear. The vehicle never had enough pressure for the rear brakes. Have the rear shoes adjusted properly if you have drum brakes. You should check to see if there is an updated part to replace the old one. If you would like to have this done, a certified technician from YourMechanic can inspect the brake system and let you know what repairs are needed.
Read Full Q/A … : Hard brake pedal and rear brakes locking up.
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 … : Hard brake pedal and rear brakes locking up.
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 … : Hard brake pedal and rear brakes locking up.
hard brake pedal with engine off no pedal when started replaced all brakes rear clyinders and master cylinder no air in lines
ANSWER : From the description provided, my first step would be double checking the connections at the master cylinder as well as double check the flexible brake lines at each wheel. A small leak can duplicate the brake pedal falling to the floor. If you are 100% certain there is no air in the system, it is very possible that your F-250 may have a faulty brake master cylinder.
The brake system on the your 1987 Ford is pretty basic and if there are no leaks, then it is VERY likely the master cylinder is the problem. If you are performing the work yourself, you may want to try exchanging your brake master cylinder for a new one.
Be sure to properly bench bleed your brake master cylinder before installing it on to the brake booster as well. I would then bleed the entire brake system at each wheel just to be sure there is absolutely no air in the system.
Of course if you did not perform the work yourself, or if you feel like you’re stuck, then I would recommend enlisting the assistance of a certified technician. They will be able to quickly determine the reason for your brake pedal falling to the floor.
Read Full Q/A … : Hard brake pedal and rear brakes locking up.
