A properly functioning braking system in any vehicle is the key to the safety of the driver, passengers and other road users. The functioning of the brakes and their effectiveness directly depends on the operation of the master cylinder. Despite the rather long service life of this unit (100–150 thousand km), some of its elements fail much earlier, resulting in the need for repair of the product.
- Purpose and functions
- Principle of operation
Video: how the master cylinder works
- GTZ malfunctions
Checking the brake master cylinder
- Removal
Video: replacing the GTZ repair kit on a “classic”
- Video: how to bleed the brake system on a “classic”
Main brake cylinder VAZ 2101
The central unit of the brake system of the VAZ 2101, like any other classic Zhiguli model, is the master brake cylinder (MBC). Due to this element, the force applied to the brake pedal is converted into hydraulic pressure in the system. We will consider the purpose, functions, malfunctions and repair work of this mechanism in more detail.
Purpose and functions
When you press the brake pedal, the GTZ pistons begin to move and compress the brake fluid, increasing its pressure. Under the influence of fluid, the brake wheel cylinders (BWC) are activated. From them come pistons that press the pads against the brake discs (front) and drums (rear). The essence of the GTZ operation is that brake fluid under pressure transmits force from the controls to the working elements.
The brake system of the VAZ 2101 consists of the following components: 1 - front brake protective casing; 2, 18 — pipelines connecting two cylinders of the front brake caliper; 3 - caliper; 4 — hydraulic drive reservoir; 5 — brake light switch; 6 — parking brake lever; 7 — adjusting eccentrics of the right rear brake; 8 — fitting for bleeding the hydraulic drive of the rear brakes; 9 — pressure regulator; 10 - brake light; 11 — rear brake wheel cylinder; 12 — lever for manual drive of the pads and expansion bar; 13 — adjusting eccentric of the left rear brake; 14 — brake pad; 15 — rear cable guide; 16 — guide roller; 17 — brake pedal; 19 — fitting for bleeding the hydraulic drive of the front brakes; 20 — brake disc; 21 - main cylinder
The master cylinder has two main functions:
- transmit mechanical action from the pedal to the wheel cylinders;
- ensure effective braking of the vehicle.
The VAZ 2101 is equipped with a GTZ, consisting of two sections, i.e., designed to work with a dual-circuit braking system. In cars with rear-wheel drive, one circuit is dedicated to the front brakes, and the second to the rear brakes. This design is convenient in that if problems arise with one of the circuits, the second will remain operational and the car can be stopped, albeit with less efficiency. The GTZ on the “penny” is located in the engine compartment next to the reservoir into which the brake fluid is poured.
The brake master cylinder is located near the clutch master cylinder and brake fluid reservoir.
Principle of operation
The main parts of the master cylinder are:
- frame;
- tank (reservoir) of the GTZ;
- piston (2 pcs.);
- return springs;
- sealing cuffs.
Brake fluid from the expansion tank is supplied to the mechanism from above via hoses. Structurally, the main distributor is divided into 2 cylinders, each of which has its own piston. A threaded plug is installed at the end facing the front of the car. On the opposite side there is a flange through which the GTZ is attached to the pedal assembly. The force from the brake pedal is applied to the first piston through the rod, and fluid is supplied to the RTC through the corresponding tubes.
The GTZ consists of the following structural elements: 1 - plug; 2 — cylinder body; 3 — rear brake drive piston; 4 — washer; 5 — front brake drive piston; 6 - sealing ring; 7 — locking screws; 8 — piston return springs; 9 — spring plate; 10 — pressure spring of the sealing ring; 11 — spacer ring; 12 — inlet; A - compensation hole (gaps between sealing ring 6, spacer ring 11 and piston 5)
The main hydraulic cylinder functions as follows:
- When the pedal is pressed, the pistons of the main cylinder begin to move and push fluid through the circuit tubes. Under fluid pressure, the wheel cylinders are activated, affecting the brake pads.
- Part of the liquid that did not have time to get into the tubes returns to the tank through special holes.
- When the driver releases the pedal, the pistons return to their original position under the force of the return springs. The liquid from the tubes and reservoir returns to the GTZ.
Video: how the master cylinder works
Which GTZ is better
When you need to replace a gas turbine engine, you have to think about which manufacturer to give preference to. Based on the practical experience of many owners of the VAZ 2101 and other “classics”, the best option is to install a standard part from AvtoVAZ with catalog number 2101–350–500–8. Other manufacturers include:
- "Basalt";
- "Belmag";
- LPR.
Cylinders from the Italian brand LPR are somewhat popular, as evidenced by numerous reviews from car enthusiasts. However, the cost of such a mechanism is slightly higher than the factory one. So, buying an AvtoVAZ GTZ will cost 750 rubles, and for LPR you will have to pay about 900 rubles. In each specific case, the choice depends on your personal preferences and financial capabilities.
The factory master brake cylinder is the best option for installation on classic Zhiguli cars.
Replacement without bleeding the brake system
Below are instructions that allow you to replace the GTZ without bleeding the brake system and without a large loss of brake fluid. To carry out repairs, you need to prepare the necessary tools and DOT-4 brake fluid.
When replacing, it is necessary to dismantle the brake fluid reservoir from the old GTZ; when dismantling it, breakdowns of the tank occur; it is recommended that when replacing the GTZ, you also purchase a new TJ reservoir.
Required tool:
- Ratchet with extension and 17mm socket;
- Open-end wrench 10mm;
- Syringe;
- Phillips screwdriver;
Step-by-step instruction
- Remove the hood seal and unscrew the interior heater insulation with a Phillips screwdriver;
- We unscrew the cap of the brake fluid reservoir and use a syringe to pump out the brake fluid into a previously prepared container;
- Using a 10mm wrench, unscrew the fittings of the TJ tubes;
- Using a ratchet with a 17mm head, unscrew the 2 nuts securing the GTZ to the vacuum booster and pull the GTZ towards you;
- We remove the tank from the GTZ (if you haven’t bought a new one). We install the reservoir on the new GTZ, lubricating the rubber seals with brake fluid;
- We install the new GTZ on the vacuum booster and fix it;
- We insert the brake fluid fittings into the GTZ, but do not tighten them;
- Fill the TJ tank up to half;
- We wait for brake fluid to flow out of the holes into which the brake pipe fittings are screwed;
- Then we twist and tighten the fittings of the TJ tubes;
- Add brake fluid between the MIN and MAX marks and close the cap;
The replacement process is complete. With this replacement, bleeding the brake system is not required.
We hope our article was useful to you.
GTZ malfunctions
The VAZ 2101 brake system has many parts that can fail due to wear, poor quality or untimely maintenance. The following characteristic symptoms of problems can be identified:
- slow stopping of the vehicle after pressing the brake pedal. One of the reasons is that the lip seals of the pistons have become unusable, which led to a loss of tightness;
- high pedal effort. This problem appears when the cuffs increase in size, for example, when installing a low-quality repair kit;
- The brake pedal has a short stroke. The working environment, i.e. the brake fluid, has nowhere to go due to the fact that the compensation hole is clogged. In addition, the canal may be blocked by swollen cuffs;
- The car only brakes when the pedal is pressed to the floor. This indicates a complete failure of the lip seals when the liquid goes into the tank and not into the system;
- Brake pads do not move away from the discs and drums, causing them to become hot while driving. The reason lies in the jamming of one of the pistons or the formation of a blockage in the bypass hole.
If the seal is lost, liquid begins to flow out of the cylinder
These symptoms may also appear in the event of problems with other parts of the braking system . For example, a pedal may fail if there is no fluid in one of the wheel cylinders or if air gets into the system. Therefore, for a final diagnosis, it is necessary to pay attention to additional features of the car’s behavior. For example, there are certain signs that clearly indicate problems with other components of the brake system, and not with the GTZ:
- pulling the car to the side when braking;
- jamming of the brake mechanisms on one of the wheels;
- the appearance of sounds uncharacteristic of normal brake operation (creaking, squeaking, grinding);
- heating of brake pads or discs on one wheel.
Checking the brake master cylinder
The most common cause of GTZ problems is wear of the seals. When replacing cuffs, you need to take into account that repairs only make sense if the piston and cylinder walls do not have wear. Otherwise, replacing the rubber seals will not bring any results and soon you will still have to install a new part. Before you start checking the main hydraulic brake drive, you should make sure that there are no problems with other elements of the system:
- Inspect the wheels from the inner surface to identify any leaks of brake fluid from the brake fluid brake system.
- Check the integrity of the tank and hoses connecting it to the gas turbine engine, as well as the presence of fluid and its level.
Fluid leaks on the inside of the wheel indicate a leak in the brake system.
A clear sign that there is a problem with the master cylinder is the appearance of liquid on the unit body . A working mechanism should always be dry without a hint of leakage. If the hydraulic drive has lost its seal, it must be dismantled for further disassembly and repair. You can determine that the gas turbine engine bypasses fluid, i.e., it does not enter the system, but returns to the expansion tank when you press the pedal:
- Open the tank lid.
- An assistant is seated in the driver's seat. The engine does not start.
- Your partner presses the brake pedal, and you listen to the sounds coming from the reservoir.
- If gurgling is heard from the container, and the pedal is pressed lightly, it means that the liquid is entering the tank instead of the system. The malfunction lies in the wear of the seals, which are unable to create the necessary pressure in the cylinder circuits.
Tools and materials needed for replacement
If you compare how much a VAZ 2107 main brake cylinder costs (from 500 to 2500 rubles), the complexity of the work and the cost of car service, it becomes obvious that it is better to replace it yourself. To do this you will only need a small set of tools and materials:
- screwdriver;
- a set of keys and sockets for 10 mm and 13 mm;
- brake fluid;
- rags;
- clamps;
- new cylinder;
- repair kit for the main brake cylinder VAZ 2107;
- rubber bulb or medical syringe at least 5 mg.
If during disassembly it turns out that the rubber hoses have lost their elasticity, these parts will also have to be replaced.
Separately, it should be noted that the lower the cost of the main brake cylinder on a VAZ 2107, the worse the safety margin of this part. If you are not willing to replace every year, there is no need to choose the cheapest parts.
