How do you fix brakes that are locking up?

Having your brakes lock up while driving can be a scary and dangerous situation. It means that your brakes have engaged but are not releasing properly, causing your wheels to skid and lose traction with the road. This article will provide an overview of the common causes of brake lockup and how to diagnose and fix the problem yourself or determine if professional repair is needed.

What Causes Brakes to Lock Up?

There are a few common causes of brakes locking up:

• Faulty brake caliper – The caliper squeezes the brake pads against the brake rotor to slow and stop your vehicle. If the caliper piston gets stuck, it can prevent the pads from retracting properly.
• Stuck brake pads – Brake pads can get contaminated with oil, grease or debris which prevents them from smoothly engaging and disengaging from the rotor.
• Faulty ABS system – The anti-lock braking system is designed to pulse the brakes many times per second to prevent lockup. If the ABS gets damaged or has an electrical issue, it may fail to release the brakes.
• Air in brake lines – Air trapped in the hydraulic brake lines can cause brakes to sporadically engage and lock up.
• Master cylinder failure – Problems with the master cylinder, which pushes brake fluid into the lines, can also cause lockup.

If just one brake is locking up, the issue is likely limited to that wheel. If all brakes are locking, there may be a more systemic problem with the master cylinder, ABS system or brake fluid lines.

Diagnosing the Cause of Locking Brakes

Start your diagnosis by performing a visual inspection of the brakes on each wheel:

• Check brake pads – Inspect thickness and condition. Make sure they move freely in caliper. Clean any contaminants.
• Inspect brake rotor – Look for damage, heavy grooves and uneven wear indicating a stuck caliper piston. A warped rotor can also cause poor braking.
• Check caliper – Look for brake fluid leaks indicating a blown seal. Make sure caliper piston is moving freely.
• Inspect brake hardware – Look for any loose, worn or damaged brake hoses, fittings and connections.

Also check the brake fluid reservoir under the hood. If the fluid level is low, there may be a leak in the brake system allowing air to enter the lines.

To further diagnose the issue, you’ll need to test drive the vehicle. Begin by driving at low speeds and apply steady pressure to the brake pedal, taking note of the following:

• Does the vehicle pull to one side when braking? This indicates a problem with one brake locking up sooner than the others.
• Do the brakes chatter, pulse or vibrate when applied? This can signal warped rotors or issues with the ABS.
• Does the brake pedal feel soft or travel too close to the floor? There may be air or leaks in the fluid lines.
• Does the brake pedal pulsate slightly when held down? The ABS system may be engaging.

Also perform hard stops from moderate speeds. Do the brakes lock up and skid? Or do they stop the vehicle smoothly? Try turning on the emergency brake to disable the ABS and test again.

Based on the symptoms and patterns during testing, you can better pinpoint what’s causing the brake lockup issue.

Fixing Sticking Brake Calipers

If one brake continuously locks and drags, the caliper piston is likely sticking and not retracting. Here’s how to fix it:

1. Remove wheel to access brake caliper. Use jack stand for safety.
2. Locate caliper bolts. There may be 1-3 depending on vehicle.
3. Remove caliper bolts and detach caliper from brake bracket.
4. Inspect piston surface for damage and contaminants. Use brake cleaner and cloth.
5. Compress piston in with a C-clamp or appropriate brake tool.
6. Inspect piston rubber seal for wear or cracks. Replace seals if needed.
7. Lubricate seals with fresh brake lubricant to prevent binding.
8. Re-attach caliper and install wheel. Check for leaks during test drive.

If the caliper is too heavily damaged, replacement may be required. Also inspect brake pads – uneven or excessive wear indicates a sticking piston over time.

Replacing Brake Pads and Rotors

Contaminated brake pads that are stuck to the rotor will need replacement. Here are the steps:

1. Lift vehicle and remove wheel.
2. Inspect rotor thickness and condition. Resurface or replace if heavily scored or warped.
3. Remove caliper bolts and hang caliper using wire.
4. Pop out brake pads from caliper bracket. Discard old pads.
5. Press caliper piston in fully with clamp tool.
6. Install new brake pads and anti-squeal shims.
7. Reinstall caliper and tighten bolts to spec.
8. Replace wheel and lower vehicle. Pump brakes until firm.

When doing brake service, it’s a good idea to replace pads on both sides of the axle for even wear. Always use quality, OEM-grade parts.

Bleeding Brakes to Remove Trapped Air

If the brake pedal feels soft and spongy, air is likely trapped in the fluid lines. Here is how to bleed the brakes to remove it:

1. Check fluid reservoir under hood. Top off with fresh, clean brake fluid as needed.
2. Start with wheel furthest from master cylinder, typically rear right.
3. Attach clear bleeder hose to bleeder valve and submerge free end in jar of brake fluid.
4. Open valve and have assistant pump brake pedal several times until fluid flows clear.
5. Tighten bleeder valve, move to next wheel and repeat process for all wheels.
6. Recheck fluid level and top off as needed. Test brakes for proper operation.

Be patient and methodical when bleeding. Adding fresh fluid from the top will push air bubbles out through the bleeder valves. Proper bleeding is crucial for a firm pedal and good braking.

Checking the Master Cylinder

Issues with the master cylinder can cause brakes to lock up on all wheels intermittently. Here’s how to test:

• Visually inspect cylinder for leaks and damage. Replace if heavily corroded.
• Check fluid level in reservoir. Keep at max line.
• Test pedal by pumping strongly several times. Pedal should be firm and not sink.
• Press pedal and have assistant check all 4 wheels for leaking fluid.
• No leaks or sinking indicates good master cylinder.

If pedal sinks or is spongy, the master may need rebuilt or replaced. Consult a repair manual for proper removal and installation.

Inspecting the ABS System

The anti-lock braking system uses a computer and wheel sensors to rapidly pulse brakes and prevent lockup. Issues can cause random locking or long stopping distances:

• Check fuse box for any blown ABS fuses. Replace any that are damaged.
• Visually inspect wheel sensors and wiring for damage. Replace parts as needed.
• At low speeds, activate ABS by braking hard on loose surface. Listen for rapid pulsating action.
• Scan for ABS trouble codes with an OBD-II scanner. Address any stored fault codes.
• No codes may indicate internal ABS hydraulic or motor faults. Seek professional diagnosis.

Be aware that ignoring ABS warning lights and continuing to drive with problems can lead to complete brake failure and dangerous situations. The ABS system should be checked over thoroughly if malfunctioning.

When to Seek Professional Brake Repair

While many brake issues can be addressed with routine maintenance, major problems will require shop repair. Seek help from a professional mechanic or technician if:

• Rotors are deeply grooved, cracked or warped beyond machining limits
• Calipers or wheel cylinders are leaking or severely corroded
• Hard brake pedal sinks to floor when held, indicating fluid loss
• ABS module sets persistent trouble codes or needs replacement
• Brake lines are cracked, swelled or leaking fluid
• Pedal pulsates after new pads and rotors installed, signaling warped components

Brake repairs require special tools and know-how to execute properly. A professional shop will diagnose issues thoroughly before recommending any needed parts or repairs.

Conclusion

Locking up brakes can make driving unpredictable and dangerous. Inspecting your brakes regularly and addressing any issues promptly can restore proper operation. Know the signs of sticking calipers, contaminated pads, low fluid, master cylinder and ABS problems. Attempting repairs yourself can save on cost, but be sure to get professional assistance for major brake system diagnoses and repairs.