In my article today I want to talk about brake pedals, namely, what it should ideally be, tight or, on the contrary, soft, how to find this golden mean?

By and large brake pedal may have several positions and states.

The first state is the one provided by the manufacturer, when when you press brake pedal there are no dips or jerks, and no special effort is required. There are also two other unpleasant pedal conditions that can cause driver concern.

This refers to the state of the pedal when it is excessively tight or, on the contrary, very soft. Both one and the second phenomenon are equally unacceptable and indicate malfunctions and the need urgent repairs braking system.

Stiff brake pedal may occur for several reasons, and they may not necessarily be associated with the traditional “sores” that are typical for all brake models. However, I still propose to consider the most common of them, and I will also try to give practical advice on how to eliminate them.

2. Sticking of the valve body in the vacuum booster. The vacuum booster needs to be replaced;

3. Damaged diaphragm vacuum booster. Solved by replacing the vacuum booster;

4. Faulty vacuum booster tip. The tip must be replaced;

5. Sticking or malfunctioning check valve in a vacuum booster. To eliminate, it is necessary to replace the check valve;

6. The check valve of the vacuum booster is faulty or the seal is broken, resulting in fuel entering the chamber of the vacuum booster. The vacuum booster with check valve should be replaced;

7. Damage to the hose that connects the vacuum booster and intake manifold, or the hose fastening on the fitting is loose. It can be treated by replacing the hose, or, if possible, by tightening the fastening clamp. The condition of the hose should be regularly monitored, this is especially true in the cold season. As long as the hose is cold, it retains the necessary rigidity - the brakes function normally. However, after several tens of minutes of motor operation, the hose heats up and becomes more elastic. If, for example, during inspection you do not find delamination, the capacity of the hose will decrease, which in turn can cause problems with the brake pedal.

8. The sealing rings in the working wheel cylinders are swollen; this often occurs as a result of contact with their surface. fuels and lubricants, or as a result of the use of poor quality brake fluid. To correct this situation, it is necessary to repair the working brake cylinders and replace the brake fluid

Here are several ways to independently check the performance of the vacuum booster.

First of all, make sure that there is a vacuum in the system. After this, press the brake pedal; if the pedal is hard, this is a clear sign of a faulty hose or amplifier. Then turn off the engine and wait 5-7 minutes, do not press the brakes.

It is necessary to specify the malfunction; to do this, press the pedal. If it is still hard, most likely the fault lies in the vacuum booster valve.

There is also another test. When the engine is not running, it is necessary to depress the brake pedal several times in order to remove the vacuum in brake system. After this, without releasing the pedal, you need to start the engine; if the pedal begins to move down a little, the amplifier is in order.

Cause of soft brakes

A soft brake pedal, as a rule, simultaneously indicates several breakdowns in the brake system. More precisely, there are many reasons why the brake pedal can become soft. Sometimes this phenomenon is also called brake pedal failure.

The brake system of Gazelle cars is two-circuit with a hydraulic drive. The first circuit includes the front disc brakes, and the rear circuit consists of two drum brakes and an adjuster braking forces("witch"). Malfunctions in the brake system can occur due to the poor quality of individual components and incorrect driver actions when performing repair work braking system.

One of the “diseases” of the Gazelle brakes is the activation of the brake drive from the second stroke. The culprit for this malfunction is the piston thrust rings located in the rear brake cylinders. Due to the poor quality of their manufacture, they lose their elasticity during the operation of the car, as a result of which the tension spring of the pads moves them together with the piston to the middle of the cylinder. In this case, the gap between the brake pads and the brake drum increases and one press of the brake pedal is not enough for the pads to press against the brake drum. Therefore, the driver has to press the brake pedal a second time.

If the brakes are activated only after several presses on the brake pedal, then this will indicate that the hydraulic drive is not sealed, and the place where the brake fluid flows from it is taken up by air. Before you start pumping the hydraulic drive, you need to find the location of the brake fluid leak and fix it. You need to start removing air from the system from the right rear brake cylinder, then left rear, right front and end with front left.

If you are not the first owner of a Gazelle car, and if air gets into hydraulic drive There's no way you can upgrade it. Then pay attention to the front brake calipers. It is possible that when repairing the brake system, the calipers were swapped, installing the right instead of the left, and the left instead of the right. In this case, the valves with which air is removed will be located at the bottom and during bleeding, it will not be possible to remove air from the caliper. To eliminate this malfunction, you will have to rearrange the calipers so that the valves are located at the top.

The main brake cylinder can also be the culprit for brake system failure. You can check its correct functioning as follows. To identify its malfunction, you will need another person to press the brake pedal. At this time, you should unscrew the cap of the nutrient reservoir where the brake fluid is located and see if it gushes out when you press the brake pedal. If so, the brake master cylinder will have to be replaced.

Remember the importance of regularly checking your brake system. Most drivers check their brakes after a problem has already arisen, meaning the brake discs, pads and other brake system components have not been inspected in a timely manner.

Here is a brief overview of the main problems with the braking system:

Low brake fluid level

Usually indicates a leak in the brake system, which can lead to very serious consequences. It is necessary to check the calipers, brake hoses and tubes, and the master cylinder. If a leak is detected, the defective component must be replaced with a new one. The vehicle should not be driven until repairs have been made, as a leak could lead to complete brake failure.

Brake pedal at the very bottom

This can happen on drum brakes if the adjusters that compensate for the normal wear of the working material of the pads are stuck. An adjustment may restore the pedal to normal level, but the problem will return as the pads wear further. It is recommended to clean the regulators well or replace them with new ones. A low brake pedal can also be caused by worn brake hoses or a brake fluid leak.

Soft or “cotton” brake pedal

Indicates that there are air bubbles in the brake system that got there due to improper bleeding of the brakes or due to a leak or very low level of brake fluid. It is necessary to bleed the brakes in the sequence intended for this car model. Another cause could be worn rubber brake hoses that “inflate” when braking.

Large pedal free play

Possible causes: worn brake hoses, improperly adjusted drum brakes, or air in the system. This symptom is quite dangerous, since the car may completely lose its brakes before it can stop safely.

The pedal goes to the floor

A very dangerous situation caused by severely worn seals in the master cylinder or a leak in the hydraulic system that prevents the brakes from holding pressure.

Brake pedal runout

Indicates that the disc is bent - it needs to be replaced or sharpened. The running surfaces must be flat (no more than 0.05mm runout) and parallel (within 0.0127mm for most vehicles). Also don't forget about the wheel bearings - if they can be serviced, they need to be cleaned, checked and re-lubricated. You will also need new wheel bearing seals.

Scraping noise

Usually indicates that metal is rubbing against metal and you are facing serious unscheduled brake repairs. Most likely will need replacement brake discs and/or drums, as well as repair or replacement of other parts of the brake system (hoses, caliper guides). Some disc brake pads have special metal wear indicators that make this sound. This means that the brake pads are already in need of replacement.

Squealing or squeaking

Typically caused by vibration between the disc pads and the caliper. It is treated by replacing or regrowing brake discs, installing new pads, or applying a special anti-noise compound to the rear surfaces of the pads.

Rattling

Usually caused by installing incorrectly machined discs.

Brake sticking

Oil, grease or brake fluid on the pads can cause the brakes to grab. Find and eliminate the cause of the contamination and replace the pads. Drums or discs with deep scratches may also seize and may require resurfacing or replacement.

Brake jamming

May cause the vehicle to pull to one side and/or increase fuel consumption. May be caused by weakened or broken springs in the drum brakes, a stuck rusty or worn guide in the caliper, a stuck cylinder in the caliper, improperly adjusted wear compensators in the drums, or stuck or frozen cables hand brake. It is necessary to overhaul the calipers every 60,000 km (uneven wear of the inner and outer pads can serve as a signal for such a overhaul).

Car pulls to the side when braking

Can be caused by: dirty pads, incorrect brake adjustment, breakage of the cylinder or the entire caliper, jamming of the brakes on one side, uneven wear brake discs on the sides of the vehicle or worn wheel bearings.

Hard (“oaky”) brake pedal

Insufficient vacuum boost can be caused by low manifold vacuum, a leak in the brake booster vacuum line, or a defect in the brake booster itself. Sometimes a broken check valve causes vacuum to leak from the brake booster, resulting in a hard brake pedal. Diagnostic procedure: release the vacuum from the system with the engine turned off, start the engine with the brake pedal pressed - if the pedal “goes away”, then the amplifier is in order. If the pedal remains hard when the engine starts, you need to pay attention to the amplifier, the amplifier vacuum tube and the check valve.

On vehicles equipped with the Hydroboost boost system, a hard pedal may be the result of a stretched power steering belt, low fluid levels, leaks in the hydraulic system pipes, or broken valves in the Hydroboost device itself.

These problems, especially brake fluid leaks, are especially critical nowadays, since the vast majority of modern cars are equipped with ABS system. This system is a complex combination of electrical and hydraulic components that cannot withstand moisture or corrosion.

Brake fluid

Brake fluid is highly hygroscopic, meaning it easily absorbs water (moisture). When moisture is absorbed, the boiling point of the liquid decreases significantly, it boils much earlier and the brake system fails. The fluid must be changed every 2 years or 60,000 km.

The brake system is one of the key ones in a car. Its malfunction or incorrect operation makes it impossible to operate the machine. Vehicles with broken brakes are prohibited by law from driving on the roads - this is extremely dangerous. Regardless of how exactly the malfunction manifests itself on your specific car: whether the steering wheel vibrates, whether the car pulls to the side when braking, or whether brake fluid is oozing from the hose. We have collected 10 sure signs of brake problems that require immediate repair.

How do brakes work?

To understand what can happen to the braking system, let's first understand how it works. In all modern cars this assembly includes brake discs or drums and pads that mechanically slow down vehicle. When the driver presses the brake pedal, the driver mechanically moves the piston in the master cylinder, then the brake fluid, moving along the lines, actuates the wheel brake cylinders. Those, in turn, press the pads with a special friction composition against the discs or drums - the car begins to slow down. The system also includes a vacuum brake booster, which minimizes pedal pressure, and a brake fluid expansion tank. Many cars are equipped electronic system, which prevents the wheels from locking during braking, known as ABS.

10 most common problems

1. Wear brake pads

Brake pads are the most unreliable element of the brake system and require regular replacement. In a disc brake system, the pads operate without problems for an average of 40 thousand km, after which they are replaced with new ones as a set. This is due to the design of the part. The pad is a metal plate with an abrasive pad. The latter wears off over time from contact with the cast iron disk, turning into dust. Often it also collapses from overheating or simply peels off from the base. Characteristic sign malfunctions - decrease in brake fluid level in expansion tank or squeaking and grinding noises when braking. This clearly hints that the pads require replacement.

2. Wear of brake discs and drums

Exactly the same applies to brake discs and drums. These parts last on average twice as long as the pads. That is, the brake disc or drum can withstand two sets of pads, after which it must be replaced with a new one. The wear limit for these parts is indicated by the manufacturer in the documentation and should not be exceeded by the consumer. For this reason, the popular service of turning brake discs can be classified as a relatively honest taking of money from motorists - as a rule, this is a disservice. Other signs of the need to replace discs are vibrations on the steering wheel when braking and a discolored part, indicating severe overheating. The latter leads to warping and worsening deceleration, and even to the impossibility of correct operation of the ABS.

3. Leaks in the hydraulic line

One of the most dangerous brake failures is depressurization. brake line. It manifests itself quite simply: when you press the pedal, the pedal goes to the floor almost without resistance, and the car does not noticeably slow down. If this happens to your vehicle, stop immediately using the engine or mechanical parking brake and use extreme caution. Find the leak and replace the damaged tube or hose, then bleed the system. Driving a car with such a malfunction is deadly!

4. Wear and jamming of the caliper guides, misalignment of the brake cylinder

The pistons of the working brake cylinders and the caliper guides oxidize over time and may begin to jam. This leads to deterioration of braking and its unevenness. This is manifested by the car pulling to the side when you press the brake pedal. Often, jamming leads to overheating of the discs and drums, as well as increased wear of the brake pads. This problem has a significant impact on safety and needs to be addressed as soon as possible. Driving is especially dangerous in winter and in rainy weather - it can cause your car to suddenly turn around.

5. Deformation of brake discs

Brake discs are usually cast iron. And this material, as you know, does not like sudden temperature changes. Be careful not to let them overheat, especially when driving along mountain serpentines or towing a heavy trailer. It is not recommended to force fords with very hot discs - this can lead to their bending and the need for premature replacement. We have already mentioned the symptoms of the problem - vibrations on the steering wheel when decelerating, an increase in braking distance and premature activation of the ABS system.

6. Weak slowdown

Weak deceleration usually occurs due to severe wear on the brake pads, discs and drums, but there are other reasons. This may be a result of overheating and boiling of the brake fluid. In this case, performance is restored as soon as the mechanisms reach normal temperature. Also, deterioration in braking can occur due to depressurization of the vacuum brake booster or jamming of the master brake cylinder. These parts must be replaced with new ones.

7. Smoke and burning smell from brakes

Smoke or a strong smell coming from the brakes is a sure sign of overheating and imminent failure of the brake system. Overheating leads to the formation of scale on surfaces, which interferes with the normal operation of mechanisms. Also bad smell and smoke may occur due to contact with the brake mechanisms technical fluids and lubricants. All this requires immediate inspection and elimination of the cause of the malfunction.

8. Malfunction light on dashboard

The brake system malfunction icon lights up on the dashboard if the brake fluid level in the expansion tank has dropped to a critically low level. Usually the problem is eliminated by adding fluid to the normal level, but this may also indicate the need to replace the brake pads and discs or even indicate leaks in the lines and hoses. A special pictogram also lights up on the instrument panel when the parking brake is activated.

9. Broken or kinked brake hoses

A very dangerous malfunction that requires immediate elimination. Brake hoses are made of rubber and age over time - they lose elasticity, crack, stretch, break or stretch. This leads to leaks, depressurization and airing hydraulic system, and, as a result, worsening deceleration or complete failure of the brakes. Carry out a periodic inspection of these parts and change them promptly if any of the symptoms described above occur.

10. Parking brake lever not lowered

Most drivers periodically forget to return the parking brake handle to its original position before starting to move the car. This leads to increased wear of clutches and discs, as well as overheating of the brakes. Or even lead to the linings peeling off from the brake pads. If there are rear drum brakes, the parking brake indicates the need for adjustment - this means that the automatic pad supply mechanism has become sour or broken. Deceleration on such a car will be mediocre - in fact, all the work will be done by the front brakes.