How to Diagnose a Stuck Caliper

Updated on February 28, 2019
Dan Ferrell profile image

Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology.

A stuck caliper can prevent your car from moving, and cause an unsafe situation for you and those around you.
A stuck caliper can prevent your car from moving, and cause an unsafe situation for you and those around you. | Source

When you release the brake pedal but the brakes remaiin partially applied, you have a stuck caliper, or dragging brakes. Not a nice situation for any car driver to face in the middle of the road. Often, a car owner can diagnose the problem and, sometimes, fix it using some common tools.

Here are a few of the brake problems that can cause a stuck caliper:

  • failing brake master cylinder
  • overadjusted parking brake
  • contaminated brake fluid
  • worn or collapsed brake hose
  • corrosion in a caliper assembly
  • bad return spring in a parking brake
  • overadjusted push rod in the master cylinder
  • stuck caliper piston
  • stuck brake pads

Stuck Caliper Symptoms

Usually, you'll know you have a stuck caliper when one or more of the following happens:

  1. You feel the car fighting a counteracting force when pushing forward.
  2. The car pulls to one side when you attempt to move. However, be aware that there are other reasons besides a stuck caliper for a car to pull to one side.
  3. The car pulls to the side after applying the brakes.
  4. After a few minutes of driving, you notice a burning smell or smoke coming off one or more wheels.
  5. After driving, you can feel heat around one or more of the wheel assemblies by putting your hand close to it.

Brake Maintenance Issues

Brake systems are fairly reliable if you check and service key components from time to time. But corrosion can cause problems.

For example, if the brake fluid is old, corrosion can build up inside the caliper and freeze the piston. Most often, though, a caliper becomes stuck after having the vehicle parked for some time. This allows corrosion to accumulate around the brake rotor, piston or pins on floating caliper type.

Whatever the cause, you should fix the dragging brake issue as soon as possible.

A dragging brake creates a serious road safety issue for you and those vehicles and people around you while driving.

Stuck Caliper Dangers

A stuck caliper may:

  • cause the brakes to overheat
  • damage wheel bearings
  • accelerate brake pads wear
  • cause poor acceleration
  • stress the transmission
  • cause poor brake performance
  • speed up rotor wear
  • cause the vehicle pull to one side
  • decrease personal safety on the road

Index
I. Finding the Stuck Caliper
II. Master Cylinder and Lines Diagnostic
Brake Master Cylinder and Brake Line Inspection
Brake Pedal and Push Rod Problems
III. Brake Caliper Assembly Inspection
What Type of Brake Caliper You Have
Inspecting the Brake Pads
Inspecting the Sliding Pin
Inspecting the Caliper Piston
Inspecting the Mounting Bracket
Dealing with Corroded Pads or Rotors
Sticking Rear Brakes
Dragging Wheel Bearing
IV. Testing Your Brakes
V. Avoiding an Accident

I. Finding the Stuck Caliper

Here are some pointers to help you identify the caliper(s) causing trouble:

  1. If the car pulls to the right when braking, check the front caliper on the left side, or vice versa.

  2. After driving a few minutes, stop the vehicle. Get off the car and try to feel for heat coming off each wheel. Place your hand close to the wheel assembly (without touching it). If one of the wheels feels hot, you've found the dragging brake.

  3. If you can't feel any heat around any of the wheel assemblies, raise the right rear wheel off the floor using a floor jack.

    NOTE: Sometimes the dragging issue manifests for a few minutes while driving or after applying the brakes. So you may need to plan for this diagnostic ahead of time when the problem appears. Or you can perform this inspection by applying the brakes several times with the tire/wheel assembly you want to inspect off the ground. This may help to recreate the problem.

    • Rotate the wheel by hand. The wheel should turn freely. If the wheel drags, you'll need to remove the tire assembly to inspect the brakes.
      • Compare the inner and outer brake pads on the suspected caliper. If there is a difference in the lining thickness, this is another sign your caliper is sticking.
      • Look for heat check marks (hardened and cracked areas) around the rotor. This is usually the sign of an overheating brake and a potential sticking caliper or brake pads.
  4. If necessary, repeat step three on the rest of the wheels to check the rotating condition on them. Continue with the left rear, front right and left.

Do You Smell Something Burning?

Stop your vehicle if you notice a burning smell or smoke coming from your vehicle wheels while driving. If one or more calipers are stuck, the wheel assembly can become extremely hot. This not only can cause damage to surrounding components, but start a fire.

A brake master cylinder may clog, seals or cylinder may fail.
A brake master cylinder may clog, seals or cylinder may fail. | Source

II. Master Cylinder and Lines Diagnostic

Once you know which caliper or wheel assembly is failing, you are ready to diagnose the problem.

First, it is a good idea to make an inspection and a quick diagnostic of the brake master cylinder and connecting lines.

  1. Loosen the lug nuts on the suspected wheel.
  2. Raise the tire off the ground using a floor jack.
  3. Support the vehicle with jack stand.
  4. Finish removing the tire.

1. Brake Master Cylinder and Brake Line Inspection

Often, a locking caliper is caused by problems in the brake master cylinder, brake line or brake hose. These next steps can help you isolate the problem area.

To perform the following test, you need to have the caliper or wheel assembly locked up. If necessary, apply the brakes several times with the tire/wheel assembly you want to check off the ground. This may help to lock up the caliper, if necessary.

If you can't get the caliper to lock up, continue with the steps. You may see signs that can reveal the reason for the caliper to lock up.

Also, be aware that loosening the brake line and hose may introduce air into the system. So you may have to bleed that line, if necessary.

  1. First, check the cap on the brake master cylinder. It should close tightly over the fluid reservoir and be in good condition. The cap creates a vacuum to help brake fluid flow back when the brake pedal is released.
  2. Look inside the brake fluid reservoir and inspect the fluid for contamination or foreign objects. This may cause the cylinder to clog during operation and lock up the brakes.
  3. Visually inspect the master cylinder for signs of leaks. If the cylinder is leaking, internal seals may be damaged and causing the caliper(s) to lock up.
  4. Lift the wheel/tire assembly off the ground you want to inspect using a floor jack. Secure the vehicle with a jack stand.
  5. Confirm the wheel is locked up by trying to spin the wheel.
  6. Closely inspect the brake hose for signs of damage. Pinch the hose with your fingers and feel for soft or hardened spots. This can be a sign of brake hose problems.

    A worn out brake hose may cause the internal lining to peel. Debris trapped inside the brake hose can prevent brake fluid to flow back towards the master cylinder, causing the piston to remain applied.

  7. Momentarily loosen the brake hose at the master cylinder end using a wrench. Be ready to catch brake fluid coming off the hose end using a rag.
  8. Try spinning the wheel by hand. If the wheel now spins freely or the caliper seems to get unstuck, you may have a:

    • clogged brake line (contaminated fluid)
    • a failing brake master cylinder (faulty seal or piston).
  9. Tighten the brake hose.
  10. Loosen the bleeder screw at the caliper. Catch the brake fluid with a shop rag.
  11. Try spinning the wheel by hand. If the wheel spins freely or the caliper becomes unstuck, most likely the problem is with the brake hose or caliper assembly.

Check the brake pedal mechanism and the push rod the pedal connects to.
Check the brake pedal mechanism and the push rod the pedal connects to. | Source

2. Brake Pedal and Push Rod Problems

If the problem seems to be in the upper section of the brakes (brake line or master cylinder), you might want to check the brake pedal and push rod adjustment as well.

A brake pedal with an incorrect height or a push rod that doesn't allow master cylinder piston free travel can also lock the brake caliper.

Consult your vehicle repair manual to double check on brake pedal adjustment, if necessary.

Usually, push rod problems occur after replacing the master cylinder or brake booster.

Take a close look of the caliper assembly and watch for corrosion and possible mechanical problems.
Take a close look of the caliper assembly and watch for corrosion and possible mechanical problems. | Source

III. Brake Caliper Assembly Inspection

Now, it's time to check the brake caliper assembly and related hardware. Before you start to diagnose your calipers, identify the type of brake caliper your particular vehicle model is using. This will make it easier to check the correct points in your brake assembly.

1. What Type of Brake Caliper You Have

Most vehicles on the road today use either a floating type or a fixed type brake caliper.

Floating Caliper:

The floating caliper has one cylinder and piston on one side only. The caliper slides on a couple of pins when the brakes are applied. The pins also serve to attach the caliper to an anchor plate.

Fixed Caliper:

The fixed type has pistons on both sides and doesn't move when you apply the brakes. Instead, the pistons on both sides move against the rotor.

If you need more information, consult your vehicle repair manual. It can not only help you identify your particular system, but specific components. The manual tells you how to disassemble many components, diagnose and replace parts as necessary.

If you don't have this manual, you can buy a relatively inexpensive copy from Amazon. Haynes manuals come with step-by-step procedures for many troubleshooting, repairs and replacement projects you can do at home.

A small investment now can help you save a lot of money. The manual will help you change your own oil at home, and do some simple maintenance and repairs projects at home.

The wear pattern on brake pads might indicate a frozen caliper.
The wear pattern on brake pads might indicate a frozen caliper. | Source

2. Inspecting the Brake Pads

Brake pads should not be sitting in a slanted position. If they are, remove the pads.

  1. Remove the brake caliper. You may need to remove one or two mounting bolts to remove or swing the caliper away from the mounting bracket. If necessary, consult your vehicle repair manual.
  2. Apply a dab of moly-based brake lubricant on the rail where the pads slide. But don't allow grease to get on the brake pads' lining or rotor.
  3. Replace the brake pads and install the caliper.

If you need to replace them, this other post on brake pads replacement will help you change the brake pads on your vehicle.

3. Inspecting the Sliding Pin

Usually, a sticking brake caliper may be caused by corroded pins. The problem may not be too obvious except for a slightly reduced brake power.

Another sign the pin is causing the caliper to stick is that the brake pad on the piston side has more wear than the outer pad.

  • If the caliper seems hard to retract, use a C-clamp to push the caliper away from the rotor.
  • Remove the brake caliper (see the previous section) and check the caliper rail (where it slides), bushings and pins.
  • Try removing corrosion using brake cleaner and a wire or soft brush or rag. If hardware seems worn or damaged, replace them.

During reinstallation, lubricate the pins and all contact points between the caliper and the mounting bracket and assembly using high-temperature moly-based brake lubricant. Make sure not to use too much grease or contaminate the rotor surface or brake pad linings with grease.

4. Inspecting the Caliper Piston

If the caliper piston is pushed against the pad and rotor, the piston is stuck. You'll need to remove the caliper and, possibly, replace the caliper. Sometimes it is possible to rebuild the caliper, but most car shops replace the caliper assembly to avoid future problems. If you are interested in rebuilding your caliper, take a look at the video at the end of this post for a visual procedure that may help you in the project.

  • If it is hard to remove the brake caliper with the piston in the applied position, retract the piston into its bore.
  • If the piston is hard to retract, momentarily loosen the bleeder screw on the caliper. Use a C-clamp to push the piston back in. Then tighten the bleeder screw.
  • Remove the piston from the caliper bore and examine the caliper bore, piston and seals. Consult your vehicle repair manual, if necessary.
  • If you find corrosion, you may want to replace the caliper assembly. Although it may be cheaper to rebuild the caliper, it may be more effective to install a new caliper.

5. Inspecting the Mounting Bracket

Check the caliper and mounting bracket for signs of wear. If necessary, replace them. Sometimes, a floating caliper becomes stuck on the rail due to corrosion or lack of lubrication.

If you decide to replace the caliper assembly, you may want to replace the opposite caliper as well. This will help to keep braking performance even on both front or rear wheels.

Corrosion around the brake rotor and brake pads is a common problem on stuck calipers.
Corrosion around the brake rotor and brake pads is a common problem on stuck calipers. | Source

6. Dealing with Corroded Pads or Rotors

If you are dealing with corrosion-stuck brake pads, you may need to resurface the rotor and replace the brake pads.

7. Sticking Rear Brakes

On rear brakes, it's usually the handbrake cable or the mechanism itself on each wheel that becomes stuck. This may happen when the lubricating grease has dried out or corrosion has set in around moving components.

If both rear wheels are locked up, most likely the handbrake cable is stuck.

Carefully cleaning the handbrake mechanism and applying grease to those points where moving parts make contact usually solves the problem.

Another potential cause is a faulty mechanism in the rear brakes that is causing the brakes to lock up.

8. Dragging Wheel Bearing

You may not find any visual or mechanical signs on the brake pads, rotor, or caliper assembly that can lead you to believe there's a problem with the brakes.

  1. In this case, remove the brake caliper from the rotor.
  2. Rotate the wheel by hand.
  3. If the wheel still feels hard to turn, most likely the problem is a worn out or damaged wheel bearing.

After fixing a stuck caliper, test your vehicle on a low traffic road.
After fixing a stuck caliper, test your vehicle on a low traffic road. | Source

IV. Testing Your Brakes

After making any repairs to the brake system, test your vehicle in a low traffic street. Or, better yet, take your car to an area isolated from vehicle traffic.

Drive slowly and confirm the brakes are not sticking or dragging anymore.

V. Avoiding an Accident

When dealing with a stuck caliper or dragging brakes, avoid moving the vehicle until you have fixed the problem. Even a mildly stuck brake can turn into a serious road safety issue without warning.

Use the pointers outlined in this guide to find out where the source of the problem is. In most cases, fixing a stuck caliper is a simple task and within the skills of the average car owner.

Still, it is a good idea to refer to your vehicle repair manual to learn how to remove and reassemble specific components in your vehicle, and torque bolts to specifications.

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