Brake Bleeders

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Brake Bleeding Explained

Brake bleeding is the process of purging air bubbles from hydraulic brake systems. The procedure is essential as the air bubbles are made up of compressible gas that reduces the pressure produced by the hydraulic system. Air can enter the brake system during specific types of servicing or when there is an air leak. Constant slamming of the brakes and worn out pads can also cause air to enter the braking system. Small bubbles of air develop a spongy feeling when stepping on the pedal while large amounts of air lead to braking failure. Usually, the process involves forcing bubble-free brake fluid into the system from the master cylinder to the drum brakes or disc brakes. Brakes should be bled every two or three years to keep a healthy brake system at optimal performance. Here is a look at the various brake bleeding techniques used.

What are Vacuum Brake Bleeders?

A vacuum pump is connected to an open bleeder valve, and the fluid extracted using a pump to remove the bubbles. This method of brake bleeding can be performed by one person using vacuum bleeders that utilise shop air pressure to suck the fluid from the bleeder. However, vacuum brake bleeding has certain drawbacks in that it can cause air to enter the system, leading to more problems.

What are Pressure Pumpers?

In this case, a pressure pump is connected to the master cylinder and the bleeder valves opened in a sequence until all the air in the fluid is pumped out. Special pumps use a method that ensures the brake fluid remains full during the bleeding process. Pressure bleeding units may be used to pressurise the fluid in the reservoir. The beauty of the method is that it is fast and only requires one person to perform the job.Additionally, it is ideal for older cars that have had little maintenance. With pressure bleeding, the master cylinder does not need to be stroked to push the fluid into the system. Stroking of the pedals to the floor causes the piston to move deep into the master cylinder, creating further damage. The seals may also pick up dirt and get damaged.

What is Bench Bleeding

When the master cylinder is replaced, it has to be bench bled before installation. This is because air gets trapped in the cylinder and bench bleeding is the easiest way of removing it. The fluid reservoir is filled with brake fluid and return hoses attached to the outlet ports to ensure the fluid is recycled into the reservoir while stroking the push rod. If you can’t access return pipes, you can put your finger on the outlet ports to stroke the cylinder in the vice as the piston returns. Keep doing this until there is a steady flow of fluid from each port, and then, fit the plugs in the ports and the cylinder to the vehicle. Next, you need to bleed the pipes on the master cylinder to remove air from the highest point in the system. This is achieved by cracking all the outlet pipes and depressing the pedal. Be sure to bleed the pipes before releasing the pedal and repeat the procedure until there is no air in the system.

What is Manual Bleeding of Brakes?

In this method, the master cylinder is used as a pump to remove air from the brake fluid. It is a two-man operation; one person opens and closes the pedal and the other pumps the pedal slowly. Brake bleeding is performed using a piece of clear plastic hose. One end is inserted into the fluid to prevent air from getting into the system when the bleeder is opened. The bleeder screw remains closed at the end of every stroke before releasing the pedal to ensure no air gets sucked back into the system.

Other Brake Bleeding Techniques

Gravity bleeders: It is the simplest method of replacing automotive brake fluid and relies on the concept of gravity. Gravity bleeding may not be as effective as other bleeding methods.- Pump and hold: the process involves pressing the brake pedal while opening one bleed screw at a time to allow air to escape. The bleed screw should be closed before releasing the pedal. Alternatively, you can fit a one-way valve.- Reverse bleeders: a pump is used to force out the fluid from the bleeder valve to the master cylinder. The idea here is that air rises in liquid and escapes from the braking system.

Frequently Asked Questions about Brake Bleeders

Is an anti-roll bar necessary?

An anti-roll bar, also known as a sway bar, is not strictly necessary for a vehicle to function, but it plays a significant role in enhancing handling and stability. Benefits of an anti-roll bar include:

  • Improved Handling: It reduces body roll during cornering, allowing for better control.
  • Increased Stability: It helps maintain a level stance, improving traction and grip.
  • Enhanced Safety: By minimising roll, it can prevent loss of control in sharp turns.
While some vehicles may perform adequately without one, especially in everyday driving conditions, performance-oriented cars typically benefit from having an anti-roll bar for optimal handling characteristics.

Can you bleed brakes on your own?

Yes, you can bleed brakes on your own with the right tools and technique. Here’s how to do it: Tools Needed:

  • Brake fluid
  • Wrench or socket set
  • Clear plastic tubing
  • Container to catch fluid
  • Helper (optional)
Steps to Bleed Brakes:
  1. Start by ensuring the vehicle is on a level surface and the engine is off.
  2. Locate the brake bleeder valve on each brake caliper or wheel cylinder.
  3. Attach the clear plastic tubing to the bleeder valve and place the other end in a container.
  4. Have someone pump the brake pedal several times and hold it down.
  5. Open the bleeder valve to release air and old fluid, then close it before your helper releases the brake pedal.
  6. Repeat this process until you see clear, bubble-free fluid in the tubing.
  7. Check the brake fluid level in the master cylinder and top it up as necessary.
Make sure to follow the specific instructions for your vehicle model, as procedures may vary.

How much does it cost to fix bleeding brakes?

The cost to fix bleeding brakes can vary based on several factors, including the make and model of the vehicle and the labour rates in your area. Generally, you can expect the following costs:

  • DIY Bleeding: If you choose to bleed the brakes yourself, the cost may be minimal, typically around £10 to £30 for brake fluid.
  • Professional Service: Hiring a mechanic can cost between £50 and £100, depending on the garage and the complexity of the brake system.
  • Additional Repairs: If there are underlying issues (e.g., leaks or damaged components), costs can increase significantly, potentially ranging from £100 to £500 or more.

How often should you bleed your brakes?

Bleeding your brakes is essential for maintaining optimal braking performance. It is generally recommended to bleed your brakes:

  • Every 1-2 years as part of regular maintenance.
  • Whenever you replace brake components, such as calipers or brake lines.
  • If you notice a spongy brake pedal or reduced braking performance.
  • After any brake fluid contamination or leaks.
Always refer to your vehicle's owner manual for specific recommendations related to your make and model.

What do brake bleeders do?

Brake bleeders are essential components in a vehicle's braking system. Their primary function is to remove air bubbles from the brake lines, ensuring that the brake fluid can flow freely and effectively. This process is crucial for maintaining optimal braking performance. Key functions of brake bleeders include:

  • Allowing for the expulsion of air trapped in the brake lines.
  • Facilitating the replacement of old brake fluid with fresh fluid.
  • Ensuring consistent brake pedal feel and responsiveness.
  • Preventing brake system failure due to air contamination.
Properly functioning brake bleeders contribute to the overall safety and efficiency of a vehicle's braking system.

Does anti-roll bar affect steering?

Yes, an anti-roll bar can affect steering. It plays a crucial role in maintaining vehicle stability during cornering, which indirectly influences steering response. Effects of an anti-roll bar on steering include:

  • Improved Handling: By reducing body roll, the anti-roll bar helps keep the tyres in better contact with the road, enhancing grip and steering precision.
  • Steering Feedback: A stiffer anti-roll bar can provide more direct feedback to the driver, making the steering feel more responsive.
  • Understeer/Oversteer Balance: The design and stiffness of the anti-roll bar can influence the balance of the vehicle, potentially leading to understeer or oversteer, which affects steering behaviour.

Is an anti-roll bar necessary?

An anti-roll bar, also known as a sway bar, is not strictly necessary for a vehicle to operate, but it plays a significant role in enhancing handling and stability. Benefits of an anti-roll bar include:

  • Improved Handling: It reduces body roll during cornering, allowing for better control.
  • Increased Stability: It helps maintain a level stance, improving traction and grip.
  • Enhanced Safety: By minimising roll, it can prevent loss of control in sharp turns.
While some vehicles may perform adequately without one, especially in everyday driving conditions, an anti-roll bar is particularly beneficial for performance-oriented cars or those frequently driven in challenging conditions.

How do anti-roll bars affect handling?

Anti-roll bars, also known as sway bars, play a crucial role in a vehicle's handling by reducing body roll during cornering. They connect the left and right sides of the suspension, helping to distribute weight more evenly across the vehicle. Effects on Handling:

  • Improved Stability: Anti-roll bars enhance stability by limiting the amount of body lean, allowing for better control during turns.
  • Increased Grip: By reducing body roll, they help maintain tyre contact with the road, improving grip and traction.
  • Enhanced Cornering Performance: They allow for sharper and more responsive cornering, making the vehicle feel more agile.
  • Reduced Understeer/Oversteer: Adjusting the stiffness of anti-roll bars can help balance the handling characteristics, reducing tendencies towards understeer or oversteer.

What does a bigger brake master cylinder do?

A bigger brake master cylinder increases the volume of brake fluid that can be pushed through the braking system. This can lead to several benefits:

  • Improved Brake Response: A larger cylinder can provide a quicker response when the brake pedal is pressed.
  • Increased Brake Force: It can generate more hydraulic pressure, enhancing the overall braking force applied to the wheels.
  • Better Performance with Larger Brakes: If larger brake calipers or rotors are installed, a bigger master cylinder can help maintain optimal performance.
  • Reduced Pedal Travel: It can decrease the distance the brake pedal needs to be pressed to achieve effective braking.

What does a brake master cylinder do?

The brake master cylinder is a crucial component of a vehicle's braking system. Its primary functions include:

  • Fluid Pressure Generation: It converts the force applied to the brake pedal into hydraulic pressure.
  • Brake Fluid Distribution: It distributes brake fluid to the brake calipers or wheel cylinders at each wheel.
  • System Monitoring: It often includes a reservoir to maintain the brake fluid level and may have a warning system for low fluid levels.
  • Dual Circuit Design: Many master cylinders have a dual circuit design for safety, ensuring that if one circuit fails, the other can still function.

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