How to check the clutch

There are simple methods how to check the clutch, allowing you to accurately determine what condition it is in, and whether it is time to carry out appropriate repairs. In this case, it is not necessary to dismantle the gearbox, as well as the basket and clutch disc.

Signs of a bad clutch

The clutch on any car wears out over time and begins to work with degraded performance. So, the clutch system must be additionally diagnosed when the following symptoms appear:

• On machines with a manual transmission, the clutch "grabs" when the corresponding pedal is at the top. And the higher - the more worn out is the clutch. namely, it is easy to check when the car is moving from a stop.
• Decrease in dynamic characteristics. When the clutch discs slip between each other, the power from the internal combustion engine is not fully transferred to the gearbox and wheels. In this case, you can often hear the unpleasant smell of burnt rubber coming from the clutch disc.
• Reduced dynamics when towing a trailer. Here the situation is similar to the previous one, when the disk can rotate and not transfer energy to the wheels.
• When driving from a stop, the car twitches jerkily. This is due to the fact that the driven disk has a damaged plane, that is, it is warped. This usually happens due to overheating. And overheating is caused by a serious effort on the clutch elements of the car.
• The clutch "leads". This situation is the opposite of slippage, that is, when the drive and driven discs do not fully separate when the clutch pedal is depressed. This is expressed in difficulty when shifting gears, to the point that some (and even all) gears are simply impossible to turn on. also during the switching process, unpleasant sounds usually appear.

The clutch wears out not only for natural reasons, but also with incorrect operation of the car. Do not overload the machine, tow very heavy trailers, especially when driving uphill, do not start with slippage. In this mode, the clutch operates in a critical mode, which can lead to its partial or complete failure.

If at least one of the signs listed above is detected, it is worth checking the clutch. Driving with a faulty clutch not only causes discomfort during the operation of the car, but also aggravates its condition, which translates into costly repairs.

How to check the clutch on a car

For a detailed diagnosis of the elements of the clutch system, additional equipment is needed and often their dismantling. However, before proceeding to these complex procedures, it is possible to simply and quite effectively check the clutch and make sure that it is out of order or not without removing the box. For this there is four easy ways.

4 speed test

For cars with a manual transmission, there is one simple method by which you can verify that the manual transmission clutch has partially failed. The readings of the standard speedometer and tachometer of the car located on the dashboard are sufficient.

Before checking, you need to find a flat stretch of road with a smooth surface about one kilometer long. It will need to be driven by car. The clutch slip check algorithm is as follows:

• accelerate the car to fourth gear and a speed of about 60 km / h;
• then stop accelerating, take your foot off the gas pedal and let the car slow down;
• when the car starts to “choke”, or at a speed of approximately 40 km / h, sharply give gas;
• at the time of acceleration, you need to carefully monitor the readings of the speedometer and tachometer.

RџSЂRё good clutch the arrows of the two indicated instruments will move to the right synchronously. That is, with an increase in the speed of the internal combustion engine, the speed of the car will also increase, the inertia will be minimal and is due only to the technical characteristics of the internal combustion engine (its power and weight of the car).

If the clutch discs significantly worn, then at the moment of pressing the gas pedal there will be a sharp increase in the speed of the internal combustion engine and its power, which, however, will not be transmitted to the wheels. This means that the speed will increase very slowly. This will be expressed in the fact that the arrows of the speedometer and tachometer move to the right out of sync. In addition, at the time of a sharp increase in engine speed from it a whistle will be heard.

Handbrake test

The presented test method can only be performed if the hand (parking) brake is properly adjusted. It should be well tuned and clearly fix the rear wheels. The clutch condition check algorithm will be as follows:

• put the car on the handbrake;
• start the internal combustion engine;
• press the clutch pedal and engage third or fourth gear;
• try to move away, that is, press the gas pedal and release the clutch pedal.

If at the same time the internal combustion engine jerks and stalls, then everything is in order with the clutch. If the internal combustion engine will work, then there is wear on the clutch discs. Disks cannot be restored and either adjustment of their position or complete replacement of the entire set is necessary.

External signs

The serviceability of the clutch can also be indirectly judged simply when the car is moving, namely, uphill or under load. If the clutch is slipping, then it is likely burning smell in the cabin, which will come from the clutch basket. Another indirect sign loss of dynamic performance vehicle when accelerating and/or when driving uphill.

Clutch "leads"

As mentioned above, the expression "leads" means that Clutch drive and driven discs do not fully separate when depressing the pedal. usually, this is accompanied by problems when turning on / shifting gears in a manual transmission. At the same time, unpleasant creaking sounds and rattles are heard from the gearbox. The clutch test in this case will be performed according to the following algorithm:

• start the internal combustion engine and let it idle;
• fully depress the clutch pedal;
• engage first gear.

If the gearshift lever is installed without problems in the appropriate seat, the procedure does not take much effort and is not accompanied by a rattle, which means that the clutch does not “lead”. Otherwise, there is a situation where the disc does not disengage from the flywheel, which leads to the problems described above. Please note that such a breakdown can lead to a complete failure of not only the clutch, but also lead to gearbox failure. You can eliminate the described breakdown by pumping the hydraulics or adjusting the clutch pedal.

How to check the clutch disc

Before you check the condition of the clutch disc, you need to briefly dwell on its resource. It is important to remember that the clutch wears the most in urban driving, which is associated with frequent gear changes, stops and starts. The average mileage in this case is about 80 thousand kilometers. Approximately on this run, it is worth checking the condition of the clutch disc, even if it does not cause problems outwardly.

The wear of the clutch disc is determined by the thickness of the friction linings on it. Its value is easy to determine in the course of the clutch pedal. However, before that, you need to correctly set the pedal itself. Please note that this value is different for different makes and models of cars, so the exact information can be found in the technical documentation for the car. In most cases, the clutch pedal in the idle (free) position is approximately one to two centimeters higher than the depressed (free) brake pedal.

The clutch disc wear check algorithm is as follows:

• place the machine on a level surface;
• remove the handbrake, set the gear to neutral and start the internal combustion engine;
• press the clutch pedal all the way and engage first gear;
• releasing the clutch pedal, start driving the car, while not allowing the internal combustion engine to stall (if necessary, you can add a little gas);
• in the process of starting the movement, it is necessary to notice in which position of the clutch pedal exactly the movement of the car begins;
• If vibrations begin in the housing, work must be stopped.

Based on the test results, the following conclusions can be drawn:

• If movement started when the clutch pedal was depressed up to 30% travel from below, then the disc and its friction linings are in excellent condition. Most often this happens after installing a new disc or the entire clutch basket.
• If the vehicle begins to move approximately in the middle of pedal travel - this means that the clutch disc worn by approximately 40 ... 50%. You can also use the clutch, there is no reason to worry. However, after some time it is desirable to repeat the test in order not to bring the disc to significant wear.
• If the clutch "grabs" only at the end of the pedal stroke or does not grasp at all - this means a significant (or complete) export disk. Accordingly, it needs to be replaced. In especially "neglected" cases, the smell of burnt friction clutches may appear.

And of course, the vibration of the car at the moment of starting from a place, as well as slippage of the clutch when the car is moving uphill, at the moment of gas supply, when towing a trailer, testifies to the critical wear of the disk.

How to check the clutch basket

The clutch basket consists of the following structural parts: pressure plate, diaphragm spring and casing. Signs of failure of the basket are the same as the wear of the clutch disc. That is, the car loses momentum, the clutch begins to slip, the gears turn on poorly, the car twitches at the start. Often, if the basket is damaged, the gears completely stop turning on. By simple manipulations with the machine, it will not work to determine exactly what the basket is to blame, you need to dismantle it with subsequent diagnostics.

The most common failure of the clutch basket is the wear of the so-called petals on it. They lose their springy properties, that is, they sink a little, because of which the entire clutch suffers, as the downforce on the driven disk decreases. When visually inspecting, you need to pay attention to the following things:

• Mechanical condition and color of petals. As stated above, they should all be in the same plane, none of them should be bent or turned outward. This is the first sign of the beginning of the failure of the basket.
• As for the color of the petals, when overheated, dark blue spots may appear on their metal. Often they appear due to a faulty release bearing, so at the same time it is worth checking its condition.
• Often there are grooves on the petals from the release bearing. It is believed that if these grooves are evenly spaced, and their depth does not exceed one third of the height of the petal, then this is acceptable, although it indicates that the basket will soon be replaced. If the corresponding grooves on different petals have different depths, then such a basket is clearly subject to replacement, since it does not provide normal pressure.
• If the spots from overheating and the so-called tarnish are located randomly, then this indicates an overheating of the basket. Such a spare part has probably already lost some of its functional properties, so you should think about replacing it. If the spots are located systematically, then this simply indicates the normal wear of the basket.
• In no case should there be cracks or other mechanical damage on the petals. Slight mechanical wear of the petals is allowed, the value of which is not more than 0,3 mm.
• you need to evaluate the condition of the pressure plate of the basket. If it is significantly worn out, then it is better to change the basket. Checking is carried out with a ruler (or any similar part with a flat surface) mounted on the edge. So you can check whether the drive disk is in the same plane, whether it is warped or warped. If the curvature in the plane of the disk exceeds 0,08 mm, then the disk (basket) must be replaced with a new one.
• With a dial indicator for measuring potholes, wear on the drive disc can be measured. To do this, you need to install the measuring rod on the surface of the disk. During rotation, the deviation should not exceed 0,1 mm. Otherwise, the disk must be replaced.

With significant wear on the basket, it is also worth checking other elements of the clutch system, namely the release bearing and especially the driven disk. Usually it also wears out a lot, and it is advisable to change them in pairs. This will cost more, but will ensure normal long-term clutch operation in the future.

Checking the clutch release bearing

The clutch release bearing only works when the corresponding pedal is depressed (bottom). In this position, the bearing moves slightly back and pulls the clutch disc along with it. so it transmits torque.

Please note that the bearing in the working position is subjected to significant loads, so do not keep the clutch pedal depressed for a long time. This can lead to premature failure of the release bearing.

One of the most obvious and common signs of a failed release bearing is the appearance of extraneous noise in the area of ​​​​its installation during the time when clutch pedal is depressed. This may indicate its partial failure. An exception may be the first minutes after starting the internal combustion engine in the cold season. This effect is explained by the different coefficients of expansion of the steels from which the bearing and the glass in which it is mounted are made. When the internal combustion engine warms up, the corresponding sound disappears if the bearing is in working condition.

also one indirect sign (the breakdowns listed below can be caused by other reasons) are problems with switching speeds. Moreover, they can have a different character. For example, the gears turn on poorly (you need to make a lot of effort), during the start and even the movement, the car may twitch, and the clutch may not work correctly. In such situations, it is necessary to carry out additional diagnostics of the release bearing, but having already removed the box.

Pedal Free Play Check

The clutch pedal on any car always has a certain amount of free play. However, over time or under the influence of external factors, the corresponding value may increase. First you need to decide what exactly the value of the free play at this moment the car has. And if it goes beyond the permissible limits, appropriate repair measures must be taken. For example, in a VAZ-“classic”, the full travel of the clutch pedal is about 140 mm, of which 30 ... 35 mm is free play.

Use a ruler or tape measure to measure the pedal free play. namely, the fully depressed pedal is considered to be the zero mark. further, to measure the free play, you need to press the pedal until the driver feels a significantly increased resistance to pressing. This will be the end point to be measured.

Note that free play is measured in the horizontal plane (see picture)!!! This means that you need to measure the distance between the projection of the zero point on the horizontal floor of the car and the vertical projection of the point where the force resistance begins. The distance between the specified projected points on the floor - this will be the value of the free play of the clutch pedal.

For different machines, the value of the free play will be different, so you need to look at the technical documentation for the exact information. However, in most cases, the corresponding value is in the range of 30…42 mm. If the measured value is outside the specified limits, the free play must be adjusted. usually, on most machines, a special adjustment mechanism based on an eccentric or an adjusting nut is provided for this.

How to check the clutch cylinder

By themselves, the main and auxiliary clutch cylinders are quite durable and reliable devices, so they rarely fail. Signs of their breakdown are inadequate clutch behavior. For example, the car may start moving even when the pedal is fully depressed. Or vice versa, do not move with the gear engaged and the pedal depressed.

Cylinder diagnostics comes down to checking for oil leaks from them. This happens, namely, during depressurization, that is, the failure of rubber seals. In this case, oil leaks can be found above the pedal in the passenger compartment and / or in the engine compartment opposite the place where the clutch pedal is located. Accordingly, if there is oil there, it means that it is necessary to revise the clutch cylinders.

DSG 7 Clutch Test

For DSG robotic gearboxes, the DSG-7 is currently the most popular clutch. Signs of its partial failure are usually the following:

• jerks of the car when starting to move from a place;
• vibration, both during the start and just while driving, namely, when the car is moving in second gear;
• loss of dynamic characteristics, namely during acceleration, driving the car uphill, towing a trailer;
• unpleasant crunching sounds during gear changes.

Clutches in robotic gearboxes (DSGs) are also subject to wear, so check their condition periodically. However, this is done a little differently than the classical "mechanics". namely, the DSG clutch test must be performed according to the algorithm below:

• Place the machine on a level road or platform.
• Squeeze out the brake and alternately move the gearshift (mode) handle to different positions. Ideally, the switching process should occur without significant effort, easily and smoothly, without grinding or extraneous sounds. If, when shifting, there are extraneous “unhealthy” sounds, vibrations, gears are switched with serious effort, an additional check of the DSG clutch must be performed.
• Set driving mode to D, then release the brake pedal. Ideally, the car should start moving even without the driver pressing the accelerator pedal. Otherwise, we can talk about strong wear of the clutch elements. However, in this case, the car may not move due to the wear of the internal combustion engine. Therefore, additional verification is needed.
• Acceleration should not be accompanied by extraneous rattling sounds, rattles, jerks, dips (sudden reset of acceleration dynamics). Otherwise, there is a high probability of significant clutch wear.
• With a sharp acceleration, the readings of the speedometer and tachometer should increase synchronously. If the tachometer needle goes up sharply (the engine speed increases), but the speedometer needle does not (the speed does not increase), this is a clear sign of wear on the clutch or friction multi-plate clutch.
• When braking, that is, when downshifting, their switching should also occur smoothly, without clicks, jerks, rattles and other “troubles”.

However, the best DSG-7 clutch test is performed using electronic autoscanners and special programs. The most common of them is "Vasya diagnostician".

How to check DSG clutch software

The best check of the DSG 7 robotic box is performed using the Vasya Diagnostic program. Accordingly, it must be installed on a laptop or other gadget. To connect to the car's electronic control unit, you will also need a standard VCDS cable (colloquially they call it “Vasya”) or VAS5054. Please note that the below the information is only suitable for the DSG-7 0AM DQ-200 box with a dry clutch! For other gearboxes, the verification procedure is similar, but the operating parameters will be different.

The clutch in this box is double, that is, there are two discs. Before proceeding to the diagnosis, it is worth briefly dwelling on the differences between the DSG and the manual transmission clutch, this will help to understand further diagnosis.

So, the classic "mechanical" clutch is normally engaged, that is, the driven and driving discs are closed when the pedal is released. In a robotic box, the clutch is normally open. Torque transmission is provided by mechatronics by clamping the clutch in accordance with what torque needs to be transmitted to the box. The more the gas pedal is depressed, the more the clutch is clamped. Accordingly, for diagnosing the state of a robotic clutch, not only mechanical, but also thermal characteristics are important. And it is desirable to shoot them in dynamics, that is, while the car is moving.

Mechanics check

After connecting the laptop to the ECU and launching the Vasya Diagnostic program, you need to go to block 2 called "Transmission Electronics". further - "Block of measurements". First you need to diagnose the condition of the first disk, these are groups 95, 96, 97. Using the program, you can build a graph, but you can not do this. namely, you need to pay attention to the limit value of the stroke and the current (diagnosed) limit position of the rod. Subtract them from each other. The resulting difference is the disc stroke reserve in millimeters of thickness. A similar procedure must be performed for the second disk. To do this, go to groups 115, 116, 117. Usually, on a new clutch, the corresponding margin is in the range from 5 to 6,5 mm. The smaller it is, the more disk wear.

Please note that the remainder of the first DSG clutch disc should not be less than 2 mm, and the second disk - less than 1 mm!!!

It is desirable to perform similar procedures in dynamics, that is, when the car is moving along a smooth, even road with maximum torque transmission to the box. To do this, go to groups 91 and 111 for the first and second disk, respectively. You can drive for diagnosis in D mode or in fourth, fifth or sixth gears. Dynamics must be measured on an even and odd clutch. It is advisable to first press the Graph button so that the program draws the appropriate graphs.

According to the resulting graphs, one can judge the value of the output of the working clutch rod. It is important to pay attention to the maximum allowable output. And the further the value obtained from the limit, the better (not worn out) condition the clutch discs are.

Checking temperature readings

Next you need to go to the temperature characteristics. First you need to look at the static indicators. To do this, go to groups 99, 102 for the first disk and 119, 122 for the second. From the readings, you can find out if the clutch worked in critical modes, and if so, how many hours exactly. You can also view specific temperature values ​​on the screen. The lower the temperature the clutch worked, the better, the less worn it is.

After that, you need to go to group number 98 and 118 for the first and second disks, respectively. Here you can see the value of the coefficient of adhesion, the deformation of the clutch, as well as the maximum operating temperature. The adhesion coefficient should ideally be in the range 0,95…1,00. This suggests that the clutch practically does not slip. If the corresponding coefficient is lower, and even more significantly, this indicates clutch wear. The lower the value, the worse.

.

Please note that in some cases the device may show a value greater than one! This is due to the peculiarities of indirect measurement and should not cause concern, the value should be taken as one.

The strain factor is also measured indirectly. Ideally, it should be zero. The greater the deviation from zero, the worse. The last column on the screen in this mode is the maximum disc temperature for the entire period of operation of this clutch. The lower it is, the better.

Next, you need to collect information about the temperature of the disks in dynamics. To do this, you need to go to group 126 in the program. The program draws a graph with two lines. One (yellow by default) is the first disk, that is, odd gears, the second (light blue by default) is the second, even gears. The general conclusion of testing shows that the higher the engine speed and the load on the clutch, the higher the temperature of the disks. Accordingly, it is desirable that the respective temperature value be as low as possible.

Please note that some car services offer their customers, with the help of software adaptations, to remove vibration when driving in second gear (a characteristic sign of DSG-7 clutch wear). In fact, the cause of these vibrations is something else, and adaptation in this case will not help.

The adaptation of shift points and clutch free play generally helps the operation of the box and prolongs the life of the mechatronic. During this procedure, the gear shift points are reset, the mechatron actuation pressures are adjusted, and the free and pressure calibration of the clutch discs is calibrated. Recommended perform adaptation every 15 thousand kilometers run. Although among motorists there are many who have a negative attitude towards adaptation, therefore it is up to the car owner to decide whether to adapt or not.

In parallel with clutch diagnostics using software tools, it is also worth checking other vehicle systems, namely, scanning for existing errors. namely, you can check the mechatronics itself. To do this, go to groups 56, 57, 58. If the fields presented contain numbers 65535so no mistakes.

Clutch repair

On many vehicles, the clutch system is subject to adjustment. This can be done on your own, or by contacting the master for help. If the car has low mileage on this clutch basket, then this repair method is quite acceptable. If the mileage is significant, and even more so the clutch has already been subject to adjustment, it is better to replace its discs or the entire basket (depending on the degree and extent of the breakdown).

It is better to make repairs or adjustments as soon as possible, when the first signs of breakdown appear. This will ensure not only a comfortable ride, but will also save money on expensive repairs.