If you’ve ever been in a situation where your brakes engage when you didn’t even touch the pedal — then you’ve probably experienced your brakes locking up.
But why do brakes lock up?
And what should you do when it happens?
Worry not!
This article will explain it all! We’ll also cover the signs of a lock-up and answer some helpful FAQs.
This Article Contains
- 8 Common Causes of Brakes Locking Up
- Signs That Your Brakes Are Locked Up
- What to Do When Your Brakes Lock Up
- Diagnosing Why Your Brakes Locked Up and Potential Repairs
- 3 FAQs About Brakes Locking up
Let’s get started!
8 Common Causes of Brakes Locking Up
Brakes (the drum brake and disc brake) are essential safety features for every vehicle. If something’s wrong with them, it can be dangerous.
Since prevention is better than cure, it’s important to understand what can cause a lockup.
Let’s look into the eight common culprits:
1. Adverse Road Conditions
When braking, the brake pads clamp onto the brake rotor creating friction — slowing down the wheels and stopping the car.
However, when braking on a slippery road, your car can continue to move forward even after the tires stop spinning. Rainwater or ice turns the road into a slick surface, causing the wheel to lose traction and skid.
This is more common in vehicles without an Anti-lock Braking System (ABS).
2. Bound Brake Calipers
Worn or broken brake components contribute to brake dust buildup inside the brake system. Brake dust gets caught between the brake rotor and caliper, causing the calipers to bind when braking.
Unattended bound brake calipers can overheat the pads and rotor— leading to premature brake pad and rotor wear, increasing the chance of your brakes locking up. This also applies to older vehicles that use brake shoes instead.
3. Piston Seizure
When driving a barely used or poorly maintained car, you’re probably driving around with a bad piston. An unmaintained caliper piston becomes heat sensitive and prone to seizing, causing brakes to lockup.
4. Compromised Hydraulic System
Using the wrong fluid, having excessive brake fluid in the master cylinder, unchanged old fluid, or a faulty brake valve can all lead to brake drag.
For a braking system that relies on hydraulic pressure — a damaged component (like a brake valve or brake hose) can cause the pressure in the brake system to go wrong. Using incorrect brake fluid or contaminated fluid can also produce insufficient pressure in the brake lines.
A restricted brake line or brake hose often causes self-applying brakes. The fluid gets stuck in the hose and cannot return to the reservoir. So when releasing the brake pedal, the brakes remain engaged because the hydraulic pressure is still applied.
5. Defective Master Cylinder
A defective master cylinder can also cause a lockup. The master cylinder is connected to the wheel cylinder or brake caliper at your wheels. So if the master cylinder is faulty, brake pressure isn’t distributed evenly.
A faulty master cylinder can also affect the brake pedal— it feels mushy and hits the floor even when pressed lightly.
6. Faulty Brake Booster
The brake booster is a component in the brake system that helps “boost” (multiplies) the force applied on the pedal — using your engine’s vacuum.
When the brake booster is broken, it gets stuck in boost mode and continues to apply force on the brakes even after releasing the pedal.
7. ABS Module Malfunction
A failing ABS module causes what an ABS system prevents — brake lock-up. Sometimes it can also be a defective speed sensor (or ABS sensor) sending wrong signals to the module.
An ABS module malfunction is indicated by an illuminated ABS light.
8. Accidentally Engaging the Parking Brake (Emergency Brake)
A parking brake is helpful as it keeps the vehicle stationary even after releasing the pedal. But accidentally pulling on the brake lever while driving can make the parking brake your worst enemy.
Here’s why:
- When driving at slow speeds, applying the emergency brake would be the equivalent of slamming the brake.
- Pulling the brake lever at high speeds causes a total brake lock-up, and your vehicle skids
Now that we’ve gone through the causes, let’s look at the signs of brake drag.
Signs That Your Brakes Are Locked Up
A brake lock-up can happen as you step on the brakes.
When it happens, your vehicle veers sharply to one side, the rear end fishtails, and you lose control of the steering wheel. It can also produce loud grinding noises, a burning smell, and smoke.
So what do you do when your brakes lock-up?
What to Do When Your Brakes Lock Up
The last thing you should do in an emergency is panic. Remain calm, turn on the hazard lights, and try to warn other drivers by honking your horn.
If you’re driving below 40 MPH, try pulling the brake lever to bring stop the car. But if you’re going at higher speeds, your reaction depends on the type of brakes you have.
Vehicles with anti lock brakes (ABS):
- Keep pressing the brakes, and don’t take your foot off the pedal.
- The brake pedal will vibrate and pulsate. Relax, it’s just the ABS system doing its job.
- Continue pushing on the brakes and try to steer your vehicle until it stops.
Vehicles without anti lock brakes:
- Take your foot off the pedal. Let the wheels get enough traction on the road.
- Press on the brakes repeatedly and try to control the steering wheel until they disengage or the car completely stops.
After you’ve managed to control your vehicle and park safely, contact a mechanic to inspect your brakes and run a diagnosis.
Diagnosing Why Your Brakes Locked Up and Potential Repairs
There are a few steps to follow when diagnosing brakes.
Here’s what your mechanic will do:
1. Check Brake Fluid Condition and Level
First, a mechanic verifies the fluid level and quality in the master cylinder reservoir.
If the level is below the minimum line, the mechanic refills the fluid until the maximum line.
Next, they’ll observe the condition of the fluid. Clean hydraulic fluid should be clear amber or yellow. If the fluid is darker, it’s contaminated or unchanged old fluid— and should be replaced.
They’ll also inspect if there are any leaks or blocks in the brake line and hose.
2. Inspect Brake Calipers
If the hydraulic system is in top condition, your mechanic will inspect the calipers.
They’ll inspect the caliper piston condition on the locked wheel. If it’s rusted or shows signs of aging, your mechanic will suggest repairing or replacing it as a set.
Note: Brakes should be replaced in a set (left and right) because the opposite side isn’t far behind when one is damaged.
3. Inspect Brake Discs and Pads
If the calipers are functioning correctly, the mechanic will inspect the brake discs and pads.
Worn-down brake pads can cause a stiff pedal and thin pad sensor wear. You’ll also notice loud grinding noises when braking. Additionally, it can cause your rotors to have uneven lines on the surface.
When the rotor and pads are worn-down, your mechanic would recommend a brake pad or rotor replacement.
If your rear wheel uses drum brakes instead, your mechanic will inspect the brake shoe and rear drum for signs of wear.
4. Check for Signs of Overheating
Next, they’ll check for signs of overheating. Excessive brake fade, smoking wheels, and squealing noises are some symptoms of overheating.
These symptoms can indicate that your vehicle’s wheel bearing on the faulty wheel needs replacement.
5. Inspect All Brakes and Components
Lastly, they’ll inspect the remaining front and rear brake. They’ll look for signs of irregular wear and component damage. This can include a burning smell, excessive brake dust, or bluing of the drum brakes and disc brake.
If any signs present themselves, your mechanic would suggest changing the whole brake set as well as the brakes on the opposite wheel.
Repairs for Brake Lock Up:
- Brake fluid flush: $90 – $200
- Caliper replacement: $300 – $800
- Brake pad replacement: $115 – $270
- Brake rotor replacement: $250 – $500
- Wheel bearing replacement: $200 – $800
- Brake set replacement: $300 – $800
Now, let’s answer some FAQs.
3 FAQs About Brakes Locking up
Here are some commonly asked questions about brakes locking up.
1. Can I Drive if My Brakes Are Locked Up?
No, you can’t drive when your brakes are locked up.
If your brakes are locked up, find a safe spot to stop and don’t try driving again. We suggest getting your car towed to the nearest workshop or contact your trusty mechanic for onsite repairs.
2. Can Only One Brake Lock Up?
Yes, only one of the brakes can lock up.
When only one brake locks up, it may be a bad brake caliper. If only the rear brake locks up, you might have a faulty brake valve on the rear wheel.
3. Can Trailer Brakes Lock Up?
Yes, they can.
Like any other braking system, electric brakes can also lock-up by accident or when braking.
There are several reasons electric brakes lock-up, like:
- A bad electrical ground
- Faulty wiring or shorted wires
- Faulty brake controller
Driving a trailer is a high-risk job, so thoroughly check your brake system, engine, and oil level before setting out.
Final Thoughts
Brakes locking up isn’t an incident to overlook. Brakes are an important part of your vehicle — if something’s wrong with them, they must be serviced immediately.
The easiest way is to contact a mobile mechanic, like AutoNation Mobile Service!
AutoNation Mobile Service is a mobile auto repair service that you can get with a touch of your fingertips. We offer a wide range of repairs and maintenance services to prepare your brakes for the road.
Contact us today to get your brakes looked at, and we’ll send our best mechanics over.