Brakes are locking up on my X5 but the dealer can’t find the problem.

I just left work. I got two blocks away and my front breaks seized up. I was going 35-40mph and my car skidded to a stop. I could not go forward or reverse. It was like resistance. This happened Monday as well at my job in the parking garage. Does anyone know why?

My car has 148000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
Your car is equipped with a brake assist system. It’s designed to sense a panic stop situation and tie the brakes down hard. By sensing the speed with which you shift your foot from the gas to the brake and how hard you press the brake, it decides if you are in an emergency situation and trying to stop the car in a hurry and hits the brakes hard to take up your slack. I wonder it that may be the part of the system that is malfunctioning. Whatever is wrong, there should be a stored codes in the system that will steer the technician in the right direction. It may not be a code that can be read with a generic scanner. It may require BMW specific equipment and software. If your dealer says there is nothing wrong, you need another opinion. You can get one by contacting Your Mechanic. They can send a technician to your home or office to check out your car and tell you what needs to be done.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Overheated braking system. Using the wrong brake fluid. Damaged or broken parts (calipers, brake pads, pistons, rotors, or others) Defective ABS components.
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.
The ABS is supposed to prevent your brakes from locking. The system operates through a computer in your vehicle to send messages when it senses unusual wheel decelerations. The computer reduces pressure on the wheel so the brakes will stop the vehicle. Brakes can lock up if your ABS system is faulty.
Unsticking a Seized Brake Caliper

Lubricating the parking brake system should fix that issue, and removing the pads and applying a small amount of grease to the edge should fix skewed pads. Once stuck pads have been freed from a disc, the solution is resurfacing the disc and replacing the pads.

The main cause of brakes seizing is inactivity. If a vehicle is sitting for a long period of time, especially out in the open, it`s not uncommon for the brakes to seize. This is usually a case of the pads becoming `stuck` to the disc as it becomes coated in surface rust, particularly after rain.
Why do brakes seize? Put simply, inactivity alongside corrosion are the main reasons why brakes seize. It`s not uncommon for a car`s brakes to seize if it has been left sitting idle for months – especially if it is parked outside. Brake discs can rust resulting in pads to become stuck to them or a caliper piston.
Why do brakes seize? Put simply, inactivity alongside corrosion are the main reasons why brakes seize. It`s not uncommon for a car`s brakes to seize if it has been left sitting idle for months – especially if it is parked outside. Brake discs can rust resulting in pads to become stuck to them or a caliper piston.
One of the most common causes of sticking brakes is simple: stuck brake calipers. Most vehicles use disc brakes, which include brake pads, rotors, and calipers. If the brake caliper gets stuck, you`ll notice a sticky sensation in your brakes.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

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.

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.

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.

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.

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.

My brakes were redone and since the repair they have been locking up
ANSWER : Hi There,
A few different things can cause this to happen. In some cases if the piston inside the brake calipers is damaged when replacing the pads, this can cause them to lock up this way. This can also happen if the brake line is pinched which can result in the brake fluid reaching the calipers, but not being released back to the master cylinder which forces the pad against the rotor causing it to lock up the brakes. I would suggest having an expert from YourMechanic come to your location to take a look at your brakes and make sure they are properly installed to ensure this does not continue to happen as this is could be dangerous.

abs light on brake line broke have been replace I bleed brake line but brake pad still go to the floor now wheels lock up
ANSWER : Hello. If the brake pedal is going to the floor then that means that it is not building pressure. If the brake system has been fully bled and there is no air in it then most of the time it is a bad master cylinder or it can be caused by a bad ABS module. If the brake fluid was low and if air got into the system then the only way to properly bleed it is with a scan tool that would allow you to open and close the valves in the ABS unit. Air gets trapped in these easily if the brake fluid gets low. This can also explain why the brakes are locking up. I would usually use my scan tool to bleed the system out first before going any further. I would also scan the brake control module to see what it is reading as a fault. If there is no air in the system and if there is no prominent code then I would replace the master cylinder first. If you want to check out why your brakes are locking up, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose and repair this.

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.