Wheel Cylinder (Functions, Symptoms & Replacement)

The wheel cylinder is a vital component in any drum brake system. Its purpose is to press the brake shoes against your car’s brake drums, which will cause your car to slow down.

However, what does the wheel cylinder do exactly? Is there anything that could go wrong, and most importantly, is there anything that can be done?

In this article, we’ll cover everything you need to know about wheel cylinders so you can trust it won’t fail you again.

We’ll talk about typical issues with the wheel cylinder and explain how you can fix it, and also discuss some wheel cylinder FAQs.

The wheel cylinder’s function is to generate force upon the brake shoes to bring them to proximity to the brake drum, thereby causing friction which helps to bring the vehicle to a complete stop.

How Is the Wheel Cylinder Different From a Disc Brake?

Disc brakes work quite differently from wheel cylinders. The disc brake caliper clamps a brake pad to each side of the rotating rotor to slowly slow down the vehicle.

How Common Are Drum Brakes?

A majority of new vehicles come with disc brakes. On the other hand, drum brakes are commonly found in the rear tires of former vehicles and small trucks.

Now that we have some background knowledge, let’s learn more about how the wheel cylinders are designed. It will then be easy to explain how things can go wrong afterward.

Also Read: 9 Bad Brake Booster Symptoms (& Replacement Cost)

How Does the Wheel Cylinder Work?

How Does the Wheel Cylinder Work

When you release the brake pedal, the force established by your foot is transmitted to the brake master cylinder.

The master cylinder then transforms force into hydraulic pressure, transported through a brake line to each wheel cylinder.

The coerced brake fluid in the wheel cylinder shoves the cylinder outside, squeezing each brake shoe against the spinning brake drum, bringing the wheel to a stop.

Immediately the brake pad is depressed, the return spring draws the brakes shoes away from the brake drum, shoving the wheel cylinder pistons back inside their drill.

Note: There are different types of wheels; the two single-piston designs and the dual-piston design.

Some drum brake design uses two single-piston wheel cylinders- one at the elevated part of the drum and one at the downward position, each attached to a brake shoe.

What Are the Symptoms of a Faulty Wheel Cylinder?

A faulty wheel is often tough to identify due to its location inside the brake drum.

Nevertheless, below are some bad wheel cylinder symptoms you should look out for:

  1. Your car’s brake is slow to respond
  2. You observe that your brake pad is pulpy, mushy or the pedal falls to the surface of the vehicle.
  3. Brake fluid leaks in the rare brake drum that pools near the rear wheel.
  4. The rear drum brakes drag or fail.

If you’re aware of any of these issues, you shouldn’t steer your wheel.

When your brakes are malfunctioning, it can be dangerous to drive, so avoid this danger by letting a mechanic know your location so they can come to you.

After all that has been discussed, the next question that comes to mind is; what causes a malfunctioning brake wheel cylinder?

Why Does the Wheel Cylinder Fail?

Why Does the Wheel Cylinder Fail

A wheel cylinder is composed of several running components, and there are many reasons why one of these components can stop working.

Here are five of the most common reasons why the wheel cylinder fails:

1. Failure of the Rubber Seal

The material property used in producing the wheel cylinder seals and dust boots is rubber.

Over time, the seals weaken and become vulnerable due to excess heat.

When the brakes yield, there will be a leakage in the brake fluid, the hydraulic pressure will decrease during the braking operation, and braking will be difficult.

2. Pistons That Are Worn Out

The size of your cylinder drill is supposed to be comparable to the diameter of the piston.

Nevertheless, the pistons scrape with prolonged usage and no longer match smoothly in the cylinder bore.

When this occurs, it could bring about leakage in the piston seal or the piston rocking, which can intensify wear.

3. Stuck Pistons

The wheel cylinder bore is supposed to have a smooth surface. The surface of the cylinder drill is meant to be very flattened.

Nevertheless, deterioration and dents can develop in the cylinder drill as a result of the disclosure of moisture in the brake fluid, which may cause the piston to jam.

The jammed pistons cause your drum brakes to be stuck as well, resulting in crucial braking issues in the drum brake network.

4. Pistons That Slip Out of the Bore

When a brake drum wears excessively, a vacuum can form large enough for pistons to slide out the cylinder drill completely.

With such a situation, the drum brakes won’t function at all.

5. Cracked Cylinder Body

Under pressure, older wheel cylinders can split and crack, leaking brake fluid and compromising its performance.

When pressure is applied to old wheel cylinders, they can fracture and break, causing brake fluid to leak and affecting the brake system’s function.

It might appear that a wheel cylinder is an easy component to replace, but restoring or refurbishing a faulty wheel cylinder is not straightforward because of its location and how it interacts with the drum brake component of your vehicle.

Also Read: Low Rumbling Sound When Braking (Causes & Solutions)

Wheel Cylinder Leak

The wheel cylinder is an integral part of the brake drum structure. Its function is to shove the brake shoe in opposition to the brake drum. This produces the resistance required to suspend your vehicle.

Any time you apply force against your brake pedal, there is a transportation of hydraulic pressure from the master brake cylinder to the wheel cylinder through the brake fluid inside the brake lines.

The material used to manufacture the housing of a wheel cylinder is grey cast iron, while lightweight aluminum is commonly utilized for newer vehicles.

The brake fluid has the tenacity to absorb water. When you neglect to reinstate a new brake fluid, the precipitation content steers rusting inwardly, degenerating the cylinder drill and resulting in holes.

A damaged piston seal made of rubber will quickly spoil and become soft with prolonged use. A broken piston seal allows fluid flow to flow ahead of the pistons.

When the wheel cylinder leaks, it affects your vehicle’s brakes, resulting in slow braking and soggy brake pedals.

Maintenance work and adequate services from professionals, and reinstating new brake fluid can elongate the active life of your wheel cylinder.

It is a very important step to replace the cylinder since it is a hydraulic component subject to heat and other problems relating to braking.

How To Replace a Wheel Cylinder

Wheel Cylinder Replacement

Below is a step-by-step procedure for a brake wheel cylinder replacement.

  1. Lift the car on a hydraulic lift or jack stand.
  2. Take out the rear wheels.
  3. Remove the drum and examine the inside of the brake drum.
  4. Take out the retainer springs with vice clasps from the wheel cylinder and brake shoes.
  5. Take out the brake line from the wheel cylinder with a line wrench. (From the open brake line, brake fluid will spill; to prevent excess brake fluid from leaking from the brake master cylinder, you should use a vacuum rubber cap.
  6. Loosen each wheel cylinder bolt from the backing plate.
  7. Dismount the old brake cylinder from the backing plate.
  8. Use the brake cleaner to clean the drum brake surface and components thoroughly.
  9. Replace the brake drum if necessary.
  10. Reinstate the brake shoes (or newer ones if necessary).
  11. Tighten the new cylinder onto the backplate.
  12. Reinstall the brake line, retainer springs, plungers for brake shoes, etc.
  13. Bleed the brakes through the bleeder screw and replace the brake fluid in the brake fluid reservoir.
  14. Reinstall the wheels and ensure each lug bolt is protected.
  15. Bring the vehicle down and readapt the brake shoes in opposition to the brake drum.

Note: After a wheel cylinder or brake shoe replacement, always remember to readapt your drum brakes. This helps the brake shoes settle excellently from the brake drum.

Check out this video for more tips on how to replace a wheel cylinder

Frequently Asked Questions About Wheel Cylinder

What Happens When a Wheel Cylinder Goes Bad?

A soft brake pedal is the first and likely distinguishable warning of a faulty wheel cylinder. A leaking wheel cylinder may compromise its ability to supercharge and lengthen the piston. As a result, the brake feels strangely soft, as if it was falling to the ground when it was released.

What Does the Wheel Cylinder Do?

The wheel cylinder is an integral part of the brake drum system. Its function is to press the brake shoes against the brake drum. This generates the friction required to stop your vehicle.

Can You Drive With a Bad Wheel Cylinder?

It is not advisable to drive with a faulty brake wheel cylinder because if the wheel cylinder is faulty, the brake fluid will leak as the result of the interior defect, and the brake pedal may fall to the ground, preventing braking. So it is not safe to steer your car with faulty brakes.

Should I Replace Both Wheel Cylinders?

If you notice a defective wheel cylinder, you can change one. To access the wheel cylinder, you can hit the self-adjuster to move the shoes off.

How Much Does It Cost to Replace a Wheel Cylinder?

Brake wheel cylinder replacement cost ranges from $200 to $350 for parts and labor costs. The cost of Labor ranges from $100 to $150. At the same time, Parts cost varies from $50 $65.

How Many Wheel Cylinders Does a Car Have?

The number of wheel cylinders is dependent on the number of drum brakes your vehicle has and the brake cylinder layout utilized. Two dual-piston wheel cylinders are commonly found in vehicles with drum brakes.

How Long Does a Wheel Cylinder Last?

You can expect your wheel cylinders to last around 3-5 years, or up to approximately 100,000km. Your vehicle’s make and model, as well as how you drive, will determine how long it will last.

Will My Brakes Still Work if the Wheel Cylinder Fails?

Yes, your brakes will still function, but you will still be unable to feel the brakes when you apply them.

Scott Greene is a seasoned automotive technician for over 5 years and has been deep into advanced automotive diagnostics for a couple of years. He Loves writing about Automotive Diagnostics and Repair, Trouble codes, Buyer guides for various car parts and accessories, and lots more. 

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