Refusal brake at the time of the beginning of movement often signals a critical drop in pressure in the contours, which in classical models VAZ is directly related to the failure of the vacuum amplifier or violation of the tightness of its connections. The immediate cause of a sharp failure of the pedal when the engine is running is a rupture of the membrane inside the body brake-powerer or jamming the pusher rod that transmits force to the main cylinder. Owners of the LADA Classic family (models 2101-2107) must immediately stop operating the vehicle, as the loss of vacuum dilution increases the force on the pedal by 4-5 times, making emergency stops almost impossible.
To accurately determine the fault of the node SED (Sosnovsk Electrotechnical Plant) or its analogues, it is necessary to conduct a primary visual check of the condition of the vacuum supply hose and the integrity of the return valve. Often the problem lies not in the mechanism itself, but in cracks on the pipe connecting the intake manifold and the amplifier, which is easy to diagnose by hearing the characteristic hissing of air when pressing the pedal. If no external leaks are detected, and the braking efficiency remains low, the unit is required to dismantle to conduct a deep defect of the internal components.
Recovery process brake-line requires a strict sequence of actions and the use of a specialized tool for adjusting the output rod. Incorrect adjustment of the length of the pusher relative to the piston of the main cylinder leads to either incomplete unbrake of the wheels or to the appearance of free pedal running, which is equally dangerous for road safety. Below are detailed technical recommendations that allow you to perform quality repair or replacement of the unit with your own hands in the garage.
Design features and principle of operation of vacuum amplifier
Basis of work vacuum-amplifier (WUT) on VAZ cars is the use of the pressure difference between atmospheric air and the vacuum in the intake manifold of the engine. Structurally, the device is a sealed housing divided by an elastic membrane into two chambers: vacuum and atmospheric. When pressed on the brake pedal, the control valve blocks the vacuum chamber's communication with the atmosphere and opens the channel for supplying atmospheric air to the second chamber, creating a pressure drop that moves the membrane and the pusher.
The key element of the system is return-valvebuilt into the amplifier body or mounted separately on the hose. Its task is to maintain the vacuum in the vacuum chamber even after the engine stops, providing several effective presses on the brake pedal when the engine is off. Violation of the tightness of this valve leads to the rapid disappearance of the vacuum and, as a result, to a sharp increase in the force necessary for braking immediately after engine jamming.
The rod exiting the amplifier body is mechanically connected to the pistons. master-cylinder (GTC). The most important parameter during assembly is the adjustment of the gap between the amplifier rod and the GTC piston. If the gap is too large, there is an increased free pedal stroke; if the gap is absent or negative (the rod rests on the piston), the brake pads will not completely move away from the discs, causing overheating and accelerated wear.
⚠️ It is strictly forbidden to operate a car with a damaged membrane or a leakproof vacuum amplifier body, as this creates a direct threat to the life of the driver and passengers due to the ineffectiveness of the braking system.
Technical characteristics of the membrane
The membrane material is a special oil-resistant rubber with a fabric cord, providing elasticity at temperatures from -40 to +80 degrees Celsius. The resource of the element is about 100-150 thousand kilometers of mileage, but it decreases sharply when aggressive liquids (brake fluid, gasoline) hit rubber surfaces.
Diagnosis of malfunctions: symptoms and methods of checking
First sign of malfunction vacuum-amplifier The change in the nature of the brake pedal is a change in the movement: it becomes “tight” and requires significant physical effort to stop the car. This phenomenon is especially noticeable at the first press after starting the engine or when coasting. If to stop the car you have to literally stand up with your feet on the pedal, this indicates a complete loss of vacuum support, which can be caused by a break in the hose or failure of the diaphragm.
For primary diagnosis without removing the node, you can use the method of multiple pressing. When the engine is silenced, press the pedal 3-5 times to the stop, then, holding the pedal in the pressed state, start the engine. If boosterThe pedal should drop down significantly under the influence of the resulting vacuum. The absence of this effect indicates a violation of the tightness of the system or jamming of the valves inside the housing.
An additional method of verification is visual and (auditory) control. When the engine is running at idle, listen to the area of the brake pedal: the characteristic hissing sound when pressed indicates the air sucking through the cuffs of the rod or cracks in the body. It is also worth inspecting (to inspect) the place of connection of the hose with the collector - the presence of oily undertrenches can talk about the throwing of oil due to malfunction of the ventilation system of the crankcase, which is harmful for rubber parts of the VUT.
- 🔍 A sharp increase in the force on the brake pedal with the engine running.
- 🔍 Characteristic hissing of air in the pedal area or under the hood during braking.
- 🔍 Unstable operation of the engine at idling due to the sucking of unaccounted air.
- 🔍 No lowering of the pedal after starting the engine during preliminary pumping.
Preparing for replacement: security tools and measures
Replacement vacuum-amplifier On cars of the VAZ classic family requires a minimum set of tools, but mandatory safety, since the work is carried out in close proximity to the braking system. Before starting work, it is necessary to fix the car, installing recoil stops under the rear wheels, and be sure to disconnect the negative terminal of the battery in order to avoid short circuit.
The main working tool will be a set of carob and cape keys (sizes 10, 13, 17 mm), pliers and a screwdriver. For ease of access to the upper nuts of the amplifier attachment to the pedals bracket, a head with an extension and a rattle may be required. It is also necessary to prepare a container for draining residues. brake fluid And a rag for cleaning surfaces, because when the main brake cylinder is disconnected, part of the liquid will inevitably spill.
An important stage of preparation is the acquisition of quality components. Original amplifiers of production of EDMS (g. Pine Bor has proven itself as reliable products, but there are many analogues on the market. When choosing a spare part, pay attention to the presence of the manufacturer's marking and equipment - the set should contain the gasket gashc and the nuts of the attachment.
☑️ Checklist before the start of work
Step-by-step instructions for dismantling and installing the node
Withdrawal process vacuum-amplifier Starts with the detachment of the hose dilution supply from the return valve. Carefully pull the hose, trying not to damage it, and take it aside. If the valve sits tightly in the body, it can be removed by pliers, but on many VAZ models it is removed with the amplifier or remains in the hose, so act carefully.
Then we need to disconnect. master-cylinder (GTC) from the amplifier body. Unscrew the two nuts of the GTZ attachment to the WUT studs. Remove the cylinder itself completely and take it aside along with the tubes is not recommended so as not to suffocate the system and not to splash the liquid - it is enough to simply push it to a distance that allows access to the amplifier fastening nuts. Put a rag under the cylinder.
In the cabin of the car, under the dashboard on the driver's side, find the place of attachment of the amplifier rod to the brake pedal. Remove the locking puck (or take out your finger), disconnect the connection and remove the return spring. After that, in the engine compartment unscrew four nuts that attach the amplifier body to the bracket on the partition. Carefully remove the knot in the direction of the engine, watching the gasket.
Installation of new booster It is done in reverse order. It is critical to check the length of the adjusting screw of the rod. To do this, you can use the old amplifier as a reference, rearranging the tip of the rod with threads to a new node at exactly the same distance. After installing the GTC and connecting the pedal, check the free ride and, if necessary, adjust.
⚠️ Attention: When installing the GTC on a new amplifier, make sure that the gasket is installed evenly, and the nuts are tightened evenly with a cross-nakrm to avoid distortion and violation of the tightness of the system.
The main nuance of installation: The length of the threaded part of the rod should be strictly identical to the dismantled node, otherwise a complex adjustment of the gap between the rod and the piston of the GTZ will be required.
Regulation of the rod and pumping of the braking system
After installing a new one vacuum-amplifier The mandatory procedure is to check and adjust the position of the output rod. The gap between the amplifier rod and the piston of the main brake cylinder should be strictly 0.1-0.5 mm (the exact value depends on the specific VAZ model and is indicated in the manual). Insufficient gap will lead to the fact that the brakes will constantly slow down, and excessive - to the appearance of a large free pedal ride.
Adjustment is made by rotating the tip of the rod. In practice, the method of comparison is often used: the rod’s departure is measured on an old, serviceable amplifier, and a similar parameter is set on a new one. If the old node is not, use special probes or calibers. After mechanical adjustment, it is necessary to make sure that when the released pedal, the pistons of the GTC do not experience pressure.
The final stage of the work is the pumping brake to remove air that could have entered the tubes when the GTC is disconnected. Pumping starts with the wheel furthest from the main cylinder (usually the rear right), then the rear left, front right and front left. The operation is carried out until a liquid without air bubbles goes from the fitting.
| Parameter | Normative value | Unit of measurement |
|---|---|---|
| Gap of the rod WUT | 0,1 - 0,5 | mm |
| Pedal force (vacuum) | not more than 15-20 | qg |
| Pedaling up to the end | 100 - 120 | mm |
| Free pedal ride | 4 - 10 | mm |
Frequent repair errors and maintenance tips
One of the most common mistakes in replacement vacuum-amplifier is the state of the hose and the return valve. Installation of a new expensive EDMS unit on an old, cracked hose or jammed valve will reduce all efforts to zero. Always change these supplies as a set, as their resource is comparable to the resource of the amplifier itself.
Another mistake is the incorrect tightening of the nuts of the GTC fastening. Excessive force can lead to deformation of the cylinder flange or failure of the thread on the aluminum body, which will require replacing an expensive assembly. Use a dynamometer key or observe moderation when tightening, focusing on the feeling of elasticity of the metal.
For extension of service brake Check the level and condition of brake fluid regularly. Hygroscopicity of the liquid leads to the accumulation of moisture, which causes corrosion of the internal surfaces of the cylinders and cuffs. Also avoid sharp starts with an unheated engine, when the intake manifold is still low, and the load on the brakes is high.
Expert advice: When buying an amplifier, pay attention to the production date. Rubber parts age over time even in a warehouse, so the product that has been lying for more than 3 years, it is better not to buy.
How often should I change the vacuum amplifier to VAZ?
Resource vacuum-amplifier It depends on the operating conditions and quality of rubber components. On average, when using the original parts of EDMS, the node serves 80-120 thousand kilometers of mileage. However, if the car is often sun-free or used in an aggressive environment, a replacement may be needed sooner. The main indicator is the change in force on the pedal.
Can I drive with a faulty vacuum cleaner?
Technically, the car will continue to move, as braking will be carried out by mechanical force of the driver's legs through the GTZ. However, the force on the pedal will increase by 4-5 times, which in an emergency situation will not allow you to brake effectively. Driving with a faulty VUT is prohibited by traffic rules and is life-threatening.
Why does the pedal fail after replacing the amplifier?
Most likely, the system remained air, and the pumping procedure brake It should be repeated more carefully. The second reason is the incorrect adjustment of the rod, because of which the GTC pistons do not return to their original position, and the liquid is transferred to the tank. The third reason is the malfunction of the newest amplifier (membrane marriage).
Which amplifier is better: EDMS or BAU?
Both manufacturers (Sosnovsk Electrotechnical Plant and the Belarusian Automobile Plant) supply components to the conveyors of VAZ. They are comparable in quality, but EDMS products often have a slightly more accurate rod geometry. The main thing is to avoid cheap Chinese analogues without labeling, the resource of which is unpredictable.
Do I need to change the brake fluid when replacing the VUT?
Complete fluid replacement is not necessary if you carefully removed the GTZ and did not let a large volume leak. However, if the fluid has been changing for more than 2 years, it is recommended to upgrade it completely, as the system will still be open when pumping, and this is a great moment for maintenance.