servo freio

Brake Servo: Everything you Need to Know

Vehicle braking systems are vital to any vehicle, ensuring safety and control while driving. At the heart of this system is the vacuum servo or brake servo, an often-neglected part.

Also known as a brake booster, it is a component within the vacuum-assisted braking system. It plays a crucial role in amplifying the force applied to the brake pedal, rendering braking more effective.

What is it? What is the purpose of a vacuum servo? What are the symptoms of a damaged vacuum servo? Find out the answers to all these questions in this informative guide.


What is a Brake Servo?

A vacuum servo is an essential component within a vehicle’s braking system, which acts as a force amplifier, assisting drivers in applying the brakes.



What is the Purpose of a Brake Servo?

Brake servos reduce the force required to apply the brakes, rendering a vehicle’s braking system more responsive and efficient. Thanks to this part, drivers are able to stop their vehicles easily and in a controlled manner, even in emergencies.

In addition, this component contributes to reducing braking system component wear, such as brake pads, prolonging their service life.


What are the Components of the Brake Servo?

The system consists of several essential parts that work together to amplify the force applied to the brake pedal, such as:

  • Vacuum chamber: contains the vacuum generated by the vehicle engine until it is released into the servo chamber when the brake is applied;
  • Servo chamber: houses all internal components;
  • Diaphragm: a flexible membrane located inside the servo brake chamber that separates the two vacuum chambers;
  • Vacuum valve: controls the flow of vacuum generated by the vehicle engine to the servo chamber;
  • Return spring: located inside the servo brake chamber to help return the diaphragm to its initial position when vacuum pressure is released;
  • Connecting rod: connects the diaphragm to the brake pedal mechanism.


How do Brake Servos work?

Brake servos operate using the vacuum pressure generated by the vehicle’s engine.

When the driver steps on the brake pedal, a vacuum valve in the vacuum servo opens, allowing the vacuum into the servo chamber. This creates a pressure difference between the two ends of a diaphragm inside the servo, causing it to move.

In turn, the movement of the diaphragm amplifies the force exerted by the driver on the pedal, transmitting it to the braking system.

As a result, the brakes are applied more efficiently and with less force from the driver, ensuring safe, controlled braking.


What is the Difference between a Brake Servo and a Master Cylinder?

Brake servos amplify the force exerted by the driver on the brake pedal, making braking easier. In turn, the master cylinder generates the hydraulic pressure that activates the braking force on the wheels.

Both play complementary roles in a vehicle’s braking system to ensure that it comes to a stop safely and effectively.


What Maintenance and Care Does a Brake Servo Require?

If you want to delay replacing the part for as long as possible, you must take into account some tips to extend the service life of your vehicle’s brake servo, such as:

  • Inspect it regularly;
  • Check fluid levels;
  • Replace hoses and fittings;
  • Lubricate components;
  • Perform preventive maintenance as regularly as recommended by the manufacturer.


What are the symptoms of a broken Brake Servo?

The main of brake servo symptoms failure are:

  • Stiff or soft pedal;
  • Strange noises;
  • Lower brake efficiency;
  • Braking system failure light on the dashboard;
  • Increased braking system response time when stopping the vehicle.


The Brake Servo is Leaking Air into the Pedal: Now what?

If the problem with your brake servo is the air outlet, you should fix it as soon as possible, as this could lead to the braking system becoming compromised, as well as your safety on the road.

If you notice that the vacuum servo is leaking air into the pedal, bring your car to a stop in a safe location and call a tow truck or your trusted mechanic.

Servo vacuum replacement is a complex task that requires advanced mechanical skills. As such, we recommend you seek out an experienced mechanic in a car repair shop.



How to Replace Brake Servo?

The steps involved in replacing a vacuum servo are as follows:

  1. Turn off your car battery;
  2. Remove vacuum hoses and brake connections;
  3. Unscrew the servo vacuum using wrenches and sockets to loosen it from the fastenings securing it to the engine bay;
  4. Remove the old component and install the new one;
  5. Refill the braking system fluid;
  6. Assemble the braking system according to the instructions;
  7. Test the system once the new component is installed.


How Can You Repair the Brake Servo?

The steps required to repair this component are similar to those required to replace it. However, the difference is that only worn or damaged parts are replaced.


How Can you Tune your Brake Servo?

Tuning a vacuum servo involves adjusting the brake pedal to get the desired response. It is a delicate process that should be carried out by an experienced mechanic.

In general, it can be adjusted by turning an adjustment screw located on the vacuum servo, which controls the amount of assistance provided to the brake pedal. Rotating the screw clockwise makes the pedal softer, while turning it counterclockwise makes it stiffer.

The pedal is adjusted in small increments and inspected to ensure that it is firm but allows for effective braking.


Which Tools Are Useful for Replacing and Repairing a Brake Servo?

Some tools that can be useful in a car garage to change the vacuum servo are:

  • Wrench and socket set;
  • Screwdriver;
  • Adjustable or open-ended spanner;
  • Brake diagnostic tools;
  • Vacuum servo repair kit (seals, diaphragms, among others).


Where Can You Buy a Brake Servo?

You can find this component in car parts shops or at car dealerships.


How much do Brake Servos cost?

The price of a vacuum servo varies from tens to hundreds of euros.

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