clutch failure
clutch failure the car is outwardly expressed in its slipping, jerky operation, noise or hum, vibration when turned on, incomplete turning on. it is necessary to distinguish between breakdowns of the clutch itself, as well as the clutch drive or the box itself. The drive is mechanical and hydraulic, and each of them has its own design features and problems.
The clutch itself consists of a basket and a driven disk (s). The resource of the entire kit depends on several parameters - the quality of manufacture and the brand of the clutch, its technical characteristics, as well as the operating conditions of the car, and namely, the clutch assembly. Usually, on a standard passenger car, up to a mileage of 100 thousand kilometers, there should be no problems with clutch.
Clutch fault table
| Evidence | Causes |
|---|---|
| Clutch "leads" (discs do not diverge) | The options are:
|
| Clutch slips | Testifies about:
|
| Jerks of the car during clutch operation (when starting the car from a place and when switching gears in motion) | Possible failure options:
|
| Vibration when engaging the clutch | May be:
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| Noise when disengaging the clutch | Worn or damaged clutch release/release bearing. |
| Clutch won't disengage | Happens when:
|
| After depressing the clutch, the pedal remains in the floor. | It happens when:
|
Major clutch failure
Clutch failures should be divided into two categories - clutch failures and clutch drive failures. So, the problems of the clutch itself include:
- wear and damage to the lining of the driven disk;
- deformation of the driven disk;
- oiling of the driven disc linings;
- wear of the splines of the driven disk;
- wear or breakage of damper springs;
- breakage or weakening of the diaphragm spring;
- wear or failure of the clutch release bearing;
- flywheel surface wear;
- pressure plate surface wear;
- seized clutch release fork.
As for the clutch drive, its breakdown depends on what type it is - mechanical or hydraulic. So, the malfunctions of the mechanical clutch drive include:
- damage to the drive lever system;
- damage, binding, elongation and even breakage of the drive cable.
As for the hydraulic drive, the following breakdowns are possible here:
- clogging of the hydraulic drive, its pipes and lines;
- violation of the tightness of the system (expressed in the fact that the working fluid begins to leak, as well as airing the system);
- breakage of the working cylinder (usually due to damage to the working cuff).
The listed possible clutch failures are typical, but not the only ones. The reasons for their occurrence are described below.
Signs of a broken clutch
Signs of a bad clutch depend on what kind of malfunctions they were caused by.
- Incomplete clutch release. Simply put, the clutch "leads". In such a situation, after depressing the drive pedal, the driving and driven discs do not open completely, and slightly touch each other. In this case, when you try to change gear, a crunch of synchronizer carriages is heard. This is a very unpleasant breakdown, which can lead to a quick failure of the gearbox.
- Disc slip. That is, its incomplete inclusion. Such a possible failure of the clutch leads to the fact that the surfaces of the driven and driving disks do not fit snugly against each other, which is why they slip between each other. A sign of a slipping clutch is the presence of a smell of burnt friction linings of the driven disk. The smell is like burnt rubber. Most often, this effect manifests itself when climbing a steep mountain or a sharp start. Also, one sign of clutch slippage appears if, with an increase in engine speed, only the crankshaft accelerates, while the car does not accelerate. That is, only a small part of the power from the internal combustion engine is transmitted to the gearbox.
- The occurrence of vibrations and / or extraneous sounds when engaging or disengaging the clutch.
- Jerks during clutch operation. They can appear both while starting the car from a place, and in the process of driving when shifting gears to a decrease or increase.
Vibrations and clutch jerks are in themselves signs of a breakdown. Therefore, when they occur, it is necessary to diagnose and fix the problem as soon as possible, so its solution will be cheaper.
How to check the clutch
If during the operation of the car there is at least one of the above signs of clutch failure, then it is necessary to further check the individual elements of this assembly. You can check the clutch on a car with a manual transmission without removing it for 3 basic breakdowns.
"Leads" or "Doesn't Lead"
in order to check if the clutch is “leading”, you need to start the internal combustion engine at idle, squeeze the clutch and engage first or reverse gears. If at the same time you have to apply significant physical effort, or a crunch or just “unhealthy” sounds were heard in the process, it means that the driven disk does not completely move away from the flywheel. You can only be sure of this by dismantling the clutch for additional diagnostics.
also one way to check if the clutch is moving is that when driving with a load (load or uphill) there will be a smell of burning rubber. It burns the friction clutches on the clutch. It needs to be dismantled and inspected.
Does the clutch slip
You can use the handbrake to check the clutch for slippage. namely, on a flat surface, put the car on the "handbrake", squeeze the clutch and turn on the third or fourth gear. After that, try to move off smoothly in first gear.
If the internal combustion engine did not cope with the task and stalled, then the clutch is in order. If at the same time the internal combustion engine does not stall and the car stands still, then the clutch is slipping. And of course, when checking, you need to make sure that during the operation of the clutch it does not emit extraneous noisy sounds and vibrations.
Checking clutch wear
Quite simply, you can check the degree of wear of the driven disk and understand that the clutch needs to be changed. namely, you need:
- Start the engine and engage first gear.
- Without podgazovyvaya, trying to move off to check the condition of the clutch disc.
- if the clutch “suffices” at the very beginning, it means that the disc and the clutch as a whole are in excellent condition;
- if the "grabbing" occurs somewhere in the middle - the disc is worn out by 40 ... 50% or the clutch requires additional adjustment;
- if the clutch is only enough at the end of the pedal stroke, then the disc is critically worn out and needs to be replaced. Or you just need to adjust the clutch using the appropriate adjusting nuts.
Causes of clutch failure
Most often, drivers encounter breakdowns when the clutch slips or is not squeezed out. The reasons for slipping can be the following reasons:
- Natural wear of the drive and/or driven discs. This situation occurs with a long run of the car, even under normal operation of the clutch assembly. namely, there is a strong wear of the friction linings of the driven disk, as well as wear of the working surfaces of the basket and flywheel.
- "Burning" the clutch. You can “burn” the clutch, for example, by frequent sharp starts with the “pedal to the floor”. Similarly, this can happen with prolonged overloads of the car and internal combustion engine. For example, when driving for a long time with a large load and / or uphill. there is also one situation - frequent driving “in buildup” on impassable roads or in snowdrifts. You can also “set fire” the clutch if you do not depress its pedal to the end while driving, trying to avoid sharp jerks and twitches. In reality, this cannot be done.
- Release bearing problems. In this case, it will significantly wear out (“gnaw”) the pressure petals of the basket.
- Vibrations of the car when starting it off (occasionally and during gear shifting) appear due to weakened damper springs of the clutch disc. Another option is delamination (warping) of friction linings. In turn, the reasons for the failure of these elements may be rough handling of the clutch. For example, frequent spinning starts, driving with an overloaded trailer and/or uphill, long periods of tight driving in off-road conditions.
The reasons listed above are typical and most common. However, there are also so-called "exotic" reasons, which are not common, but can cause a lot of trouble for car owners in terms of their localization.
- In most cases, the driven disk wears out in the clutch, which is why it is changed more often. However, when the clutch slips, it is also necessary to diagnose the condition of the clutch basket and flywheel. Over time, they also fail.
- With frequent overheating, the clutch basket loses its frictional properties. Outwardly, such a basket looks slightly blue (on the working surface of the disk). Therefore, this is an indirect sign that the clutch is either not working at 100%, or will soon partially fail.
- The clutch may partially fail due to the fact that oil that has leaked from under the rear crankshaft oil seal has got on its disc. Therefore, if the engine has an engine oil leak, then the breakdown must be diagnosed and repaired as soon as possible, since this may also affect the operation of the clutch. Getting on its disk, it, firstly, contributes to clutch slippage, and secondly, it can burn there.
- Mechanical failure of the clutch disc. It can manifest itself when trying to release the clutch while driving, even at neutral speed. Very unpleasant sounds come out of the gearbox, but the transmission does not turn off. The problem is that sometimes the disk crumbles in its central part (where the slots are located). Naturally, in this case, switching speeds is impossible. A similar situation can arise with a significant and long-term load on the clutch (for example, towing a very heavy trailer, long driving with slipping and similar frequent heavy loads).
Clutch failure repair
Clutch failures and how to eliminate them depend on their nature and location. Let's dwell on this in detail.
clutch basket failure
Failure of clutch basket elements can be expressed as follows:
- Noise when pressing the clutch pedal. However, this symptom may also indicate a problem with the release bearing, as well as with the driven disk. But you need to check the elastic plates (the so-called "petals") of the clutch basket for wear. With their significant wear, repair is impossible, but only the replacement of the entire assembly.
- Deformation or breakage of the pressure plate diaphragm spring. It needs to be inspected and replaced if necessary.
- Warping of the pressure plate. Often just cleaning helps. If not, most likely you will have to change the entire basket.
clutch disc failure
Problems with the clutch disc are expressed in the fact that the clutch "leads" or "slips". In the first case, for repair, you need to perform the following operations:
- Check for warping of the driven disk. If the end warp value is equal to or greater than 0,5 mm, then the pad on the disk will constantly cling to the basket, which will lead to a situation where it will constantly “lead”. In this case, you can either get rid of warping mechanically, so that there is no end runout, or you can change the driven disk to a new one.
- Check for jamming of the driven disk hub (that is, misalignment) on the splines of the input shaft of the gearbox. You can get rid of the problem by mechanical cleaning of the surface. After that, it is allowed to apply LSC15 grease to the cleaned surface. If cleaning did not help, you will have to change the driven disk, in the worst case, the input shaft.
- If oil gets on the driven disc, the clutch will slip. This usually happened with older cars that have weak oil seals, and oil can seep from the internal combustion engine onto the disk. To eliminate it, you need to revise the seals and eliminate the cause of the leak.
- Friction lining wear. On old disks, it could be replaced with a new one. However, nowadays car owners usually change the entire driven disk.
- Noise when pressing the clutch pedal. With significant wear of the damper springs of the driven disk, a rattle, clang coming from the clutch assembly is possible.
release bearing failure
Clutch release bearing: principle of operation, symptoms of failure
The clutch release bearing in the gearbox is engaged when the driven disk is separated from the drive disk. Having learned the principle of operation, you can understand the signs and causes of failure, and also check it yourself Read more
Diagnosing a broken clutch release bearing is quite simple. You just need to listen to his work at idle ICE. If you press the clutch pedal to the stop in neutral and at the same time an unpleasant clanging sound comes from the gearbox, the release bearing is out of order.
Please note that it is advisable not to delay its replacement. Otherwise, the entire clutch basket may fail and it will have to be replaced entirely with a new one, which is much more expensive.
clutch master cylinder failure
One of the consequences of a broken clutch master cylinder (on machines that use a hydraulic system) is clutch slippage. namely, this happens because the compensation hole is significantly clogged. To restore working capacity, it is necessary to revise the cylinder, dismantle and wash it and the hole. it is also desirable to make sure that the cylinder is working as a whole. We drive the car into an inspection hole, ask an assistant to press the clutch pedal. When pressed with a working system from below, it will be seen how the master cylinder rod pushes the clutch fork.
also, if the clutch master cylinder rod does not work well, then the pedal, after pressing it, may very slowly return or not return to its original position at all. This can be caused by a long idle time of the car in the open air, thickened oil, damage to the cylinder surface mirror. True, the reason for this may be a failed release bearing. Accordingly, to fix the problem, you need to dismantle and revise the master cylinder. If necessary, it must be cleaned, lubricated and it is desirable to change the oil.
also one failure associated with the master cylinder in the hydraulic clutch system is that the clutch disengages when the drive pedal is pressed hard. Reasons for this and remedies:
- Low level of working fluid in the clutch system. The way out is to add liquid or replace it with a new one (if it is dirty or according to the regulations).
- System depressurization. In this case, the pressure in the system decreases, which leads to an abnormal mode of its operation.
- Item damage. Most often - a working cuff, but it is also possible the mirror of the clutch master cylinder. They need to be inspected, repaired or replaced.
clutch pedal failure
The reasons for the incorrect operation of the clutch pedal depend on which clutch is used - mechanical, hydraulic or electronic.
If the car has a hydraulic clutch and at the same time it has a “soft” pedal, then the option of airing the system is possible (the system has lost its tightness). In this case, you need to bleed the clutch (bleed the air) by replacing the brake fluid.
On a mechanical clutch, often the reason that the pedal falls "to the floor" is that the clutch fork has worn out, after which it is usually put on the hinge. Such a breakdown is usually repaired by welding the part or simply by adjusting it.
sensor failure
The sensor is installed on the electronic pedal in the respective clutch system. It informs the control unit about the position of the specified pedal. The electronic system has the advantages that the control unit, in accordance with the position of the pedal, corrects the engine speed and regulates the ignition timing. This ensures that switching takes place under optimal conditions. This also helps to reduce fuel consumption.
Accordingly, with a partial failure of the sensor, jerks occur when shifting gears, when starting the car from a place, fuel consumption increases, and the engine speed begins to “float”. Typically, when the clutch pedal position sensor outputs, the Check Engine warning light on the instrument panel is activated. To decode the error, you must additionally connect a diagnostic tool. The reasons for the failure of the sensor may be:
- failure of the sensor itself;
- short circuit or breakage of the signal and/or power circuit of the sensor;
- misalignment of the clutch pedal.
usually, problems appear with the sensor itself, so most often it is changed to a new one. Less often - there are problems with the wiring or with the computer.
clutch cable breakage
A cable-operated pedal is the lot of older clutch systems that can be adjusted mechanically. that is, by adjusting the cable, the stroke of the drive pedal can also be controlled. Information about the stroke size can be found in the reference information for the specific vehicle.
also, due to incorrect adjustment of the cable, slipping of the clutch is possible. This will be the case if the cable is very tight and for this reason the driven disk does not fit snugly against the drive disk.
The main problems with the cable are its breakage or stretching, less often - biting. In the first case, the cable must be replaced with a new one, in the second case, its tension must be adjusted in accordance with the free play of the pedal and the technical requirements for a particular car. Adjustment is carried out using a special adjusting nut on the "shirt".
electronic drive failure
Malfunctions of the electronic drive include:
- failure of the clutch pedal position sensor or other sensors involved in the operation of the corresponding system (depending on the design of the individual vehicle);
- failure of the drive electric motor (actuator);
- short circuit or open circuit of the sensor / sensors, electric motor and other elements of the system;
- wear and / or misalignment of the clutch pedal.
Before performing repair work, additional diagnostics should be carried out. According to statistics, most often there are problems with the position sensor and pedal misalignment. This is due to problems with internal contacts in these mechanisms.
Recommendations in conclusion
in order to avoid all major clutch failures, it is enough to correctly operate the car. Of course, occasionally clutch elements fail due to wear and tear (after all, nothing lasts forever) or factory defects. However, according to statistics, it is the incorrect handling of the manual transmission that most often becomes the cause of the breakdown.
