The braking system is the basis for the safe behavior of a car on any road. If it behaves abnormally, be it the main brake or the parking brake (handbrake), it is recommended to immediately eliminate the malfunction. This is directly stated in the traffic rules, and this section of the rules must be taken into account. Malfunctions can manifest themselves in different ways. For example, the brake pedal has become hard - there may be various reasons for this. But until you understand what’s going on and fix the problem, you can’t go anywhere.
Repair brake system is not a very expensive or very difficult car repair, provided there is a lift or overpass. Here are the problems that may arise in real life: traffic situation, can have the most tragic consequences. Most inexperienced drivers, accustomed to stable brake operation, are simply lost when the car does not brake with normal force, or the pedal suddenly falls. Only special training at the race track will allow you to apply proper engine braking. And the last “line of defense” is the handbrake, so it must be in good working order.
Basic design of the brake system
- The brake pedal and the levers going from it to the amplifier.
- Vacuum booster (VA) - uses rarefied air from the engine to facilitate pedal operation.
- Master brake cylinder – evenly distributes the force received from the brake control unit to each wheel. Brake fluid is used to transmit pressure.
- Metal tubes and rubber hoses - through them, fluid is pumped from the master brake cylinder to the workers.
- Brake wheel cylinders and brake pads are installed on all four wheels, they exert a braking effect on each brake disc or drum.
If the pedal is not pressed
The pedal force is facilitated by a vacuum booster.
The brake pedal is too tight - check the vacuum booster.
This means that if the pedal has become hard or is pressed too hard, the reason is related to it. This could be a simply disconnected or cracked rubber tube coming from the engine exhaust manifold. Or a breakdown of the device itself, most often associated with its depressurization.
IN in rare cases Breakdowns or disconnection of the levers may occur - this will be associated with characteristic sounds when pressing the pedal. Sometimes a foreign object or a bent part of the mat gets under the pedal.
Dips when pressing the pedal
High-quality and clean brake fluid is the key to normal brake operation. It is thanks to its high density that the braking force is quickly transmitted to the wheels. Over time, it deteriorates its properties, air bubbles form in it, and moisture accumulates.
If the brake pedal is either soft or hard, check the level brake fluid.
If a slight depressurization occurs in any area, the liquid flows out and air gets in its place. As a result, the brake pedal is either soft or hard. Several gentle pressures lead to the accumulation of pressure in an insufficiently dense liquid. Then it works, and effort appears.
First of all, you need to check for the presence of liquid in expansion tank brake system, it is located on the master cylinder. If there is no liquid in it, you cannot drive; simply refilling it will not solve the problem. If you are planning do-it-yourself repair, you have to find the location of the leak - it could be any of the cylinders or some kind of tube.
Brake operation when the engine is off
The pressure on the pedal is related to the vacuum booster. And the VU itself can only work with the engine turned on. When parked for a long time, the pressure in the vacuum chamber becomes atmospheric - the amplifier does not work. When you press the pedal, the force is transmitted directly from the levers to the master cylinder. The resistance on the pedal increases by 3-5 times.
A hard brake pedal after parking is normal.
If you start the engine while holding down the pedal, it should fall slightly. You can go safely.
Control for technical condition a car is a conscious necessity for any driver who wants to ensure the safety of himself and others.
The article will talk about what to do when the brake pedal becomes too soft or, on the contrary, too tight. When the brake pedal stops working normally, becomes harder or softer, the driver’s concern is completely justified. This means that there are some malfunctions and the brake system needs to be repaired. And you can’t put it off.
If the brake pedal suddenly becomes tight, there are several reasons for this, although they are not necessarily typical or traditional for all models and types of brakes.
The main reasons for a soft or stiff brake pedal and methods for solving them
In most cases, the brake pedal becomes soft due to problems with the master cylinder or vacuum booster.
It is much cheaper and easier to systematically diagnose brakes, so as not to spend money on repairs later. Because brakes fail at the most inopportune times, remember this.
The brake pedal must be pressed with increased force for several reasons:
- air filter vacuum booster is clogged. In this case, the air filter must be replaced; · the valve body in the vacuum booster is stuck, there is only one way out - replace the vacuum booster;
- it may be that the diaphragm in the vacuum amplifier is damaged, then the amplifier needs to be changed;
- malfunction of the tip of the vacuum booster - you need to change the tip;
- the check valve in the vacuum booster does not work or is stuck, so fuel enters the cavity of the vacuum booster. In this case, it is necessary to change not only the vacuum booster, but also the check valve;
- The hose that connects the vacuum booster and the intake manifold is damaged, or the hose fastening in the fitting is loose.
You will need to change the hose or tighten the mounting clamp. If we talk about the vacuum booster hose, then you need to constantly monitor its condition. Especially in winter. The hose will be quite stiff until it is warmed up. The brakes work fine. The hose will heat up after the engine has been running for a short time, and it will become more elastic. If the delamination of the hose is not noticeable, its throughput will decrease.
There may be problems with the brake pedal;
O-rings in wheel (working) cylinders may swell. This can happen if fuels and lubricants get into them or if low-quality brake fluid is used. Brake fluid and wheel cylinders should only be replaced with those recommended by the manufacturer.
Methods for checking a vacuum booster
There are several ways to check the vacuum booster. First you need to start the engine. A vacuum will be created in the system. Next they press the brakes. If the brake pedal is hard, then there is a fault in the hose or booster. You need to turn off the engine and wait 5 minutes, but do not apply the brakes.
To specify the malfunction, you need to press the pedal. If it continues to be hard, then in most cases there is a problem with the vacuum booster valve.
There is another way. The engine must be turned off. To relieve the vacuum in the brake system, press the brake pedal several times. Then the engine is started, but the brake pedal is not released. If the pedal goes down, then there is no problem with the amplifier.
The second problem is the soft brake pedal. This may indicate several malfunctions at once. More precisely, there are several reasons why the brake pedal can become soft. Soft brakes mean the brake pedal sinks.
Causes of soft brakes
- The brake system is “aired”. It will be necessary to remove all the air, that is, bleed the brake system. The cause of air ingress may be a depressurization of the system or a low level of brake fluid in the expansion tank;
- there may be a malfunction in the master brake cylinder;
- the last option is problems with the working cylinder. Such problems may be due to boiling of the brake fluid or jamming of the piston. In this case, you need to replace the brake fluid or repair the brake cylinders.
The most important organ in any car is the brake system. It must be in perfect condition, because our lives depend on it. One of the main indicators of the efficiency of this unit is the pedal, which must always differ in the state of pressing that is familiar to the foot. This rule cannot be neglected and if the slightest changes occur, adjustments or repairs must be made immediately. Below we will look at what needs to be done when the brake pedal becomes hard, does not press at all, or grabs at the very end of its stroke. We will also pay attention to the issues self-diagnosis and we will study all the reasons for failure this mechanism.
Causes of brake pedal failure
Changes in the degree of effort to press the pedal occur due to a number of design violations, which can be either universal for all types of cars, or defects exclusively in certain models or series. We will consider a list of the main problems that can be called typical for modern and Soviet cars. As a rule, failure of the brake pedal is a consequence of a malfunction of the vacuum booster or brake master cylinder. Detailed analysis performance and changes in the brake system will allow us to identify the true source:
The VU air filter is clogged. This element is not cleaned. If a significant amount of foreign substances gets inside, which affects performance, it is necessary to replace the amplifier with a new analogue.
Mechanical damage to the VU valve body. With minor defects, the mechanism begins to jam, which affects the force of pressing the pedal. Such a breakdown, unfortunately, cannot be repaired, but requires replacement of the amplifier.
Damage to the VU diaphragm. A sign of the presence of this defect may be extraneous sounds when the braking system is activated. The damage is corrected by replacing the amplifier.
The tip of the VU is faulty. This reason can also cause the brake pedal to catch at the end of its stroke. To fix the problem, unlike previous breakdowns, replacement of the main element is not required. It is enough to install only a new tip.
The check valve does not work or gets stuck - this can be eliminated by replacing this mechanism. Depressurization of this segment leads to fuel entering the cavity of the amplifier. In the future, this disables the entire unit. As a result, you need to change the control unit complete with the check valve.
Damage or loosening of the hose connecting the VU to intake manifold. In the first case, the rubber tube needs to be replaced, and in the second option, the fastening clamps will have to be tightened or replaced if damaged. This reason is the most common and requires regular monitoring and inspection of fastening reliability. The condition of the hose must be checked regularly. It is made of a special polymer, which becomes rigid when cooled, but after turning on the engine and warming up, the material becomes flexible. Because of this, its throughput is reduced. As a result of this problem, problems arise in the operation of the brake pedal. To avoid this problem, you need to purchase high-quality parts with specific thermal parameters.
Swelling of sealing rings in cylinders. If the brake pedal is not pressed, you should immediately check the condition of the elastic seals. Most often this happens due to gasoline and oil getting inside the components or using low-quality brake fluid. Depending on the degree of damage, seals and low-quality brake fluid are replaced with an analogue recommended by the manufacturer.
Video - Why the brake pedal does not work
Diagnosis of brake pedal operation
The correct state of pressure for the leg can be viewed from different aspects. However, there can only be one answer. In an effective and fully functional system, the pressing force always remains the same, there are no exceptions to this rule. It should be understood that uncharacteristic sounds are also a sign of failure. They arise in the process of mechanical action on the lever, while the pressing force can remain unchanged. In such cases, you need to contact specialists or carry out independent repairs.
Methods for diagnosing faults without special equipment
Run power unit, this will create a vacuum in the brake system. Then press the pedal. If it is still hard, the amplifier or hose is faulty.
Turn off the engine and, without pressing the brake, wait 4-6 minutes. After the time has passed, press the pedal. If the lever has not lost its rigidity, the VU valve is most likely faulty.
With the engine off, depress the pedal several times. These actions will relieve the vacuum in the brake system. Press the pedal to its extreme position and start the engine. If the pedal goes down a little, then there are no problems with the VU. The latter method allows you to most effectively test the performance of the amplifier.
Diagnosing depressurization is very simple. A sign of this problem is the unstable operation of the engine, as they say it “troubles”. The reason for this is air entering the intake manifold. In the process of depressurization, it becomes sharply depleted air-fuel mixture. If the pedal does not press when the car is running, first of all you should check the reliability of the connections. A sign of this breakdown is also a characteristic hissing sound from the vacuum booster when the engine is running.
The information described above will help in solving the problem with the “hardening” of the brake pedal. If you find any changes, do not delay repairs and fix the damage as soon as possible. You must always remember that the safety of all road users depends on the effectiveness of the braking system.
Details Published: 06/13/2012 05:26The study of the most classic defects in the brake system of a car continues, which are determined using a brake testing stand. Such a component brake control, like a stiff and soft brake pedal (problems and solutions), includes a pair of states of its position. The first is normal, when the pedal is pressed without noticeable changes, without dips, jumps, without special efforts, and so on. The next two circumstances of the pedal position are unpleasant for the driver, and which cause specific anxiety.
It is said that when the brake pedal becomes stiff or, on the contrary, the brakes are very soft. In this situation, when the brake pedal stops working normally, the driver’s worry is justified. This indicates that some defects have arisen and the brake system needs to be repaired. At the same time, without putting it off for a long time.
There may be a couple of reasons why the brake pedal has suddenly become tight, and they are not necessarily traditional and typical for all types and brands of brakes. Despite this, the key, most common causes and ways to eliminate them are considered.
Most of the defects that cause a stiff and soft brake pedal are “to blame”: either the cryogenic booster or the main brake cylinder. Increased effort when pressing the brake pedal is due to the fact that the air filter of the cryogenic amplifier has become dirty.
In this case, you need to change the air filter; jams the valve body in the cryogenic amplifier. The solution is to change the cryogenic amplifier; The partition of the cryogenic amplifier is broken.
Change the cryogenic amplifier; faulty tip of the cryogenic amplifier - the tip needs to be changed; the opposite valve in the cryogenic amplifier is jammed or does not work, the opposite valve needs to be replaced; The check valve of the cryogenic amplifier is faulty (leaky), which allows fuel to enter the cavity of the cryogenic amplifier.
It is necessary to replace the cryogenic amplifier complete with the opposite valve; the hose that connects the cryogenic amplifier to the intake manifold is broken, or the hose is loosened on the fitting. The hose is changed or the fastening clamp is tightened. Learn more about the cryogenic brake booster hose.
Its condition must be monitored regularly. Especially in the cool season. As long as the hose is not steamed, it remains somewhat stiff, and the brakes work normally. After running the engine for a short time, the hose heats up, becomes more elastic, and its throughput decreases. There may be a problem with the brake pedal.
The sealing rings in the working cylinders are swollen. This can happen due to the penetration of fuels and lubricants into them, or the use of low-quality brake fluid. Repair workers brake cylinders, change the brake fluid to the one recommended by the manufacturer.
Several methods for checking the performance of a cryogenic amplifier:
Start the engine. A vacuum occurs in the system. Then he presses the brake. A hard brake pedal indicates a defect in the amplifier or hose. After stopping the engine, wait about five minutes without pressing the brake.
Specification of the defect. Pressing the pedal. If the pedal remains hard as before, then it is most likely a faulty cryogenic booster valve.
With the engine turned off, it is worth pressing the brake pedal a couple of times to remove the discharge in the braking system. Without releasing the brake pedal, you need to start the engine. If the stiff and soft brake pedal (problems and solutions) goes down a little, then everything is fine with the booster.
A soft brake pedal can indicate several defects. Namely, there are a couple of reasons why the brake pedal has suddenly become soft. This effect can also be called: failure of the brake pedal.
A stiff and soft brake pedal (problems and solutions) have traditional causes: “airing” of the brake system. Of course, air must be removed, namely in the form of bleeding the brake system.
The reason for “airing” is possible: once the system is sealed or lowest level brake fluid in a wide reservoir; defect of the main brake cylinder: defect of the working cylinder, for example, as a result of a stuck piston or boiling of the brake fluid. The brake cylinders need to be repaired or the brake fluid needs to be replaced with new one.
