The structure of the braking system (Mondeo 3)

Two main, independent braking systems (foot brake and handbrake) are prescribed by the Technical Requirements for the Operation of Non-Railway Transport (StVZO). The reason: if one system fails, the other system can always brake the vehicle and reduce its power. The braking system of your Mondeo has a diagonally divided braking system - a separate brake circuit connects one front wheel and the diagonally opposite rear wheel respectively: if one of the circuits fails, the front and rear wheels of the other circuit ensure the braking process. With only one active brake circuit, your Mondeo will stop significantly later than usual. You will notice the failure of one of the circuits, however, not only by the extended braking distance, but also by the increased travel of the brake pedal and the lit indicator light on the instrument panel.

Anti-lock braking system (ABS), emergency braking system (EBA), traction control system (TCS), electronic brake force distribution (EBD), electronic stability program (ESP)

ABS and TCS increase active driving safety, EBD replaces the mechanical brake force regulator and EBA (optional) increases the initial brake pressure during emergency braking. The ABS function retains full control capability even under full braking, TSC improves directional stability during acceleration on rough roads. Electronic brake force distribution (EBD) and emergency braking system (EBA) have become other active safety components in modern braking configurations. EBD is active before ABS, it increases braking stability by electronically precisely adjusting the slip of the rear wheels. The emergency braking system determines, depending on the speed at which the brake pedal was pressed, whether full braking or completely normal braking occurs. If the symbol is set to "full braking", EBA increases the brake pressure automatically to the maximum possible value - even when the brake pedal is not yet fully pressed. The brake assist is thus an assistant in reducing the braking distance – perhaps by a crucial few centimetres. The anti-lock braking system used in the Mondeo comprises an electronic and hydraulic control unit (HECU). Both systems are housed in a common aluminium housing. The HECU is used to precisely record the wheel speeds, with a separate sensor installed at each wheel: EBD and TCS use the same signals. The HECU works with eight electromagnetic valves, a hydraulic, DC-driven injection pump and two low-pressure accumulators. In the Mondeo, all wheels can be adjusted individually up to a speed of 120 km/h. On the rear axle, the wheel that is first suitable for locking is used as a "reference". If system errors occur, ABS, EBA, EBD and TCS are switched off – the braking process then functions without its "assistants", like a normal braking system. Interference in the system is detected by the ABS warning light: it no longer goes out after the corresponding self-test, but lights up constantly. The Mondeo ABS system is fully diagnostic, fault codes are archived in the permanent memory on request. In addition, Ford supplies the Mondeo with an optional ESP system.

Brake power dosing – electronic dual-circuit pump

The braking energy in the system is distributed by an electronic dual-circuit pump. Each of the four individual control channels is associated with a pair of electromagnetic valves (one inlet and one outlet valve). The inlet valves are normally open and have switchable openings (a small opening for precise regulation of small flow rates during braking contact, a large opening for minimal hydraulic resistance during normal braking).

Braking Process Analysis – EVA

EVA already recognizes at the stage of pressing the brake pedal whether such pressing is a normal procedure or caused by a panic situation on the road. In a panic situation, EVA increases the initial brake pressure automatically to the limit of wheel locking. This also helps an "inexperienced" driver to brake his Mondeo in critical situations with the theoretically shortest braking distance. If the pedal pressure drops to a programmed value, EVA switches control only to the driver. The emergency braking assistant in the Mondeo is integrated into the NBZ (main brake cylinder)/brake force booster unit.

Depends on the speed at which the brake pedal is pressed: initial brake pressure. 1 - with EVA, 2 - normal braking system, A is the maximum blocking limit, P — brake pressure, F - pedal force.

ABC Functioning Management - HECU

The HECU controls the ABS, calculates the speed based on the signals from the wheel speed sensors. It monitors all electrical components and records the parameters of failures. When the ignition is switched on, the system performs a self-test initiated by the HECU before driving. While driving, all electrical connections are under the watchful eye of the HECU. This process is carried out taking into account priorities, as well as checking the patency of individual electrical circuits. At the same time, the solenoid valves are regularly tested for functionality: the system emits an electrical impulse for this. Possible faults are quickly and specifically read at the Ford station using the WDS tester. The diagnostic connector for this is on the left under the instrument cluster.

Rear Wheel Slip Limiter - EBD

EBD limits, milliseconds before the main system is activated, the slip of the rear wheels. It constantly compares the slip on the rear and front wheels and doses or distributes the braking force accordingly. The operation of EBD is usually unnoticeable, its technology - regardless of the vehicle's load condition - implements the minimum braking distance. In addition, EBD replaces the conventional brake force regulator in the system.

Active up to 50 km/h – TCS

TCS is integrated into the Mondeo ABS system, together with two electromagnetic shut-off valves and two hydraulic inlet valves. This system is active, depending on need, up to the 50 km/h limit. Its use benefits sudden acceleration from a standstill and, in particular, when cornering, as well as the steering of your Mondeo: if TCS detects slippage of the front wheel, the rotating pneumatic tire is braked until it regains contact.

Automatically brakes individual wheels – ESP

ESP stabilizes the driving parameters in the boundary zones of dynamic properties. It supports the driver with its targeted braking grip on individual wheels or correction of engine control in relation to maintaining the course of your car. However, in spite of all theoretical prerequisites (dreams) for absolute safety – ESP is unable to establish the boundaries of the physics of motion: where the "head" fails from the very beginning, even the most modern car electronics "will be on the sidelines".

Mondeo Brakes

Ford Mondeo slows down with four disc brakes. The front, internally ventilated discs are 24 mm thick and 300 mm in diameter. 60 mm pistons grip them in a "pincer grip". The rear axle has 12 mm thick discs with a diameter of 280 mm, which are acted upon by 36 mm pistons.

In order for the floating calipers to get the right "bite" without much effort, the Mondeo has a brake booster that is directly connected to the brake pedal. Direct contact with the brake pedal also saves on the intermediate lever. The Mondeo driver notices the "missing part" at a comfortable pressure point and well-metered pressure generation in the brake system.

ABS in combination with EDB is also standard equipment for the Mondeo braking system. EDB uses the ABS sensors to detect the wheel speeds. During the braking process, the rear wheels controlled by EDB are always "given" so much brake pressure that they always brake close to the locking limit with maximum braking force. The system automatically takes into account the respective load conditions, it shortens the braking distance even outside the ABS control range.



The Mondeo ABS system, with its twelve adjustment intervals per second, is state-of-the-art. It provides, with unlimited control, maximum deceleration and forms the basis for TCS and ESP.

In low speed ranges, TCS brakes only individual wheels. At 50 km/h, TCS additionally "disturbs" the engine management: it further reduces the "fuel diet" by selecting cylinders and/or modifies ignition timing and torque until a regular traction ratio again prevails on the drive wheels.

Ford also evaluates the safety reserves of the Mondeo chassis with the help of ESP. As an interactive system, ESP reduces engine power on a progressive scale and specifically brakes an individual wheel. ESP "provokes" with its "grabbing" a yaw moment, which automatically stabilizes the car. The system works completely autonomously with its "active" brake booster.

At this point we will consciously repeat for you: ESP does not create airbags for "headless" drivers – if the limits of the physics of movement are exceeded, then "flying out" – even with ESP – is inevitable.

Four channels, twelve valves, control electronics for ABS, TCS, EBD: ESP unit. 1 - Self-priming 2-circuit hydraulic pump, 2 - Hydraulic block, 3 — Electronic control unit, 4 — Pressure sensor.

Housing - two functions: yaw rate and lateral acceleration sensor. 1 dual sensor unit.

Accurate measurement: steering wheel angle sensor. 1 — Steering column, 2 - Electromagnets, 3 - Measuring gear, 4 — CAN connection, 5 - Microprocessor, 6 — AMR element.

Overview – Brake System Elements

Brake system with dual-circuit hydraulic drive (mainly with diagonally divided hydraulic drive):

Accordingly, a separate brake circuit is established by connecting the front wheel and the diagonally opposite rear wheel.

Master brake cylinder (MBC): Converts the mechanical force of the brake pedal into hydraulic force. Ensures rapid pressure reduction in the system after the pedal is released.

Brake booster (servo brake): Located in the engine compartment in front of the brake master cylinder. During each braking process, it increases the mechanical force of pressure on the pedal by approximately 60%. In cars with ESP, an "active" brake booster is installed. As soon as the electronic stabilization program is started in the Mondeo, an electromagnetic valve is activated in the booster. Due to this, a pressure of approximately 10 bar is created on the back side of the membrane, even without pressing the brake pedal. The brake booster receives its "energy" through a hose directly from the intake manifold or a separate vacuum pump (diesel). During braking, the membrane, connected to the brake master cylinder by a piston, reacts to the difference between the outside air pressure and the low pressure in the intake manifold.

Wheel brake cylinder (WBC): the brake fluid pressure in the KTC can reach 120 bar. The KTC pistons transmit the pressure in the pipeline system to the free pistons in the calipers of the disc brake mechanisms (disc brake mechanism) or wheel brake cylinders (drum brake mechanism). The piston stroke in disc brakes is transmitted to the discs by the brake shoes or in drum brakes by the brake linings to the drum.

TECHNICAL DICTIONARY

Brakes Front axle Brake disc: rotates synchronously with the axle hub. Dissipates friction heat into the atmosphere. Disc brake caliper: in Mondeo, the floating caliper "hooks" the brake disc. To move the caliper, the piston of the brake cylinder is located on its inner side. Disc brake mechanism with floating caliper: 1 - Floating caliper, 2 - Sliding pins. Rear axle Brake disc: rotates synchronously with the axle hub. Dissipates friction heat into the atmosphere. Disc brake caliper: in Mondeo, a floating caliper with a hand brake mechanism "hooks" the brake disc. To move the caliper, there is a piston of the brake cylinder on its inner side. Pressing the brake pedal: the system pressure created in the master cylinder acts on the brake caliper piston and presses the inner brake pad in the floating caliper against the brake disc. As a result, the sliding caliper of the disc brake mechanism also moves towards this disc. Releasing the brake pedal: the hydraulic pressure drops instantly, the piston gasket pulls the piston together with the caliper away from the brake disc. A small gap appears between the brake pad and the disc – the brake disc rotates freely again. Anti-lock braking system ABS control unit: continuously processes the rotational speed signals from the wheel sensors and compares them with the programmed values. If different rotational speeds indicate an imminent danger of locking on one or more wheels, the control unit activates the hydraulic unit - the brake pressure on the corresponding wheel is reduced until it rotates synchronously with the other wheels. This variable play occurs during the entire braking process in a cycle of milliseconds. ABS components of Mondeo: 1 — Main brake unit (HCU), 2 - Rear wheel speed sensor, 3 Front wheel speed sensor. ABS hydraulic unit: consists of an electric pump and a valve block with electromagnetic valves. When you press the brake pedal in the master brake cylinder, the pistons push the brake fluid through the valve block to the wheels. At the same time, this block regulates the brake pressure in the brake lines that connect the front wheel to the corresponding diagonal opposite rear wheel. When the ABS comes into effect, the control unit issues a command to "reduce brake pressure". The brake fluid flows directly from the valve block back to the expansion tank. If the brake pressure rises again, the brake fluid flows from the expansion tank through the hydraulic pump directly into the corresponding brake circuit. As soon as the pump has started working, you will know about it by a slightly pulsating brake pedal. Wheel speed sensors: with a small gap from the toothed wheel (pulse wheel) is firmly connected to the wheel hub. The pulse wheel rotates with its toothed projections depending on the rotation of the wheel (speed) faster or slower past the sensor. Each tooth of the pulse wheel indicates a short voltage jump. Due to this, an alternating voltage arises in the sensor, which changes its frequency in accordance with the rotation frequency of the wheel. The sensors measure the rotation frequencies of the wheels and send data about them to the control unit in the form of electrical signals. Inductive speed measurement: wheel speed sensor. 1 - Output signal, 2 - Contact zone, 3 - Installation position (right rear wheel), 4 — Sensor. ESP – module: The ESP module in the Mondeo is based on the ABS module type Mk20E-I with TCS. Only here the hydraulic valve block has two other valves, with the help of which the rear wheels are slowed down separately. The ESP module communicates via the CAN data bus with the PCM. Yaw Rate/Lateral Acceleration Sensor: in the Mondeo, you can find a micromechanical dual sensor that measures the yaw rate and lateral acceleration inside the gearshift lever. During normal driving, as well as during light acceleration or deceleration, the sensor does not work. As soon as the acceleration or deceleration parameters set in the control unit are exceeded, a corresponding signal is generated in the control unit. Malfunctions of the ABS brake system: when the ignition is turned on, the ABS brake system indicator light comes on. Subsequently, with the engine running, it goes out after two seconds. If this light comes on while driving, then there is a failure in the system. Naturally, in this situation, you can continue driving - but without the participation of this "brake" assistant. To check the system, you need to quickly find a Ford workshop. Because as an "amateur" in ABS without the appropriate testing devices, you can of course check the correctness of the plug connections to the control unit, relay, wheel sensors and hydraulic unit.

Checking the brake system - if in serious doubt, an option for a workshop

On every metre of public roads, the brake system is responsible for your safety and the safety of other road users. Hence the conclusion: functioning brakes are life insurance. Therefore, do not be afraid to remove the wheels from time to time and check the condition of the brake pads and discs. Maintenance work on the brake system is not that complicated. However, "put your hands on the brakes only if" you are absolutely convinced: at the slightest doubt, "give your brakes" to a special workshop that knows all the "know-how" and where you can find the necessary tools.