Maintenance, Advice & Common Issues
Steves Auto Clinic South Africa possess more than 35 years of automotive repair knowledge. As leader in the field of automotive repairs and servicing, we deem ourselves more than qualified to address any clutch related issue. We employ qualified and well-trained mechanics (technicians) who are willing and ready to assist you with any clutch related issue at our Service Centres countrywide.
At Steves Auto Clinic, we consider every SAC client to be a part of the huge SAC family, and when it comes to prospective clients/customers, we welcome them with equal warmth and outstretched arms as part of the SAC family. Being part of this family means being cared for, that is why we want to keep everybody informed about the various components in their vehicles; not only with regard to the fair share of maintenance these components require to function smoothly and safely, but also with regard to the most common problems that these components may present you with.
We know that not everybody is as informed as the other person is, and we know from experience that not everybody possess the knowledge when it comes to component maintenance and/or the early identification of potential problems with these components. We want to rectify this. Fear of the unknown tends to cause anxiety and that is why we will highlight some aspects related specifically to one of these components today, namely the clutch system.
We want to make it clear that this article do not serve the purpose of instilling unnecessary and unfounded fear in our readers regarding the topic at hand; this article serves the primary purpose of informing our readers about what a clutch is, how to care for it and how to maintain it. We will also highlight the most common problems that a clutch may present, and how to identify these clutch related problems beforehand. In pursuing this goal, I will answer the following questions:
What is a clutch and how exactly does it work?
Are there different types of clutch systems?
How can I maintain & prolong my vehicle’s clutch life?
What are the most common issues with a clutch?
Without any further ado, let us delve right into the answering of these questions.
What is a clutch and how exactly does it work?
According to the Merriam Webster dictionary, a clutch is a coupling used to connect and disconnect a driving and a driven part of a mechanism (such as an engine and a transmission). In other words, a clutch is a mechanical device that engages and disengages the engine and transmission of the vehicle. This, in short, is the purpose of a clutch.
Every vehicle fitted with a manual transmission is fitted with a clutch; vehicles with an automatic or Tiptronic transmission make use of a hydraulic fluid coupling or a torque converter, instead of a clutch, to change gears, which is why people mostly refer to these as torque converter automatics. A torque converter connects to the Electronic Control Unit (ECU) of the engine and allows for precise control of the vehicle. I will discuss both the torque converter and fluid coupling in brief later on in the article. For the sake of knowledge, a Tiptronic (Sportmatic/Steptronic) transmission is a type of automatic transmission that allows the driver to choose whether he/she wants to drive in automatic mode (where the computer does gear shifting) or in a manual mode (where he/she has the opportunity to change gears without operating a clutch).
Back to the clutch itself. It would have been silly if a vehicle started moving the moment you started it. When you start a vehicle’s engine, the engine generates continuous power and there are parts that are in constant rotation, but the wheels are not constantly turning. What prevents the motor from engaging with the wheels (and therefore making movement of the vehicle possible), is the engagement of the clutch. The clutch contains two main parts, the clutch plate and the flywheel. The flywheel, fitted to the crankshaft, keeps on running as long as the engine is running. When the clutch engages, a set of springs help to keep a pressure plate pushed up against the clutch plate. The pressure from these springs push the clutch plate against the flywheel and this connection enables the transfer of power from the engine to the gearbox. The clutch and the engine will then rotate at equal speeds. The clutch makes this smooth engagement between the spinning engine and the non-spinning transmission possible.
Are there different types of clutch systems?
There are indeed different kinds of clutches. A clutch is the essential link between the engine and the drivetrain; with all the different engine types, it is not strange that the automotive world will have many engine-transmission combinations from which to choose. Clutches can take many shapes and forms and are mostly divided into two main categories: Friction & Hydraulic clutches.
Friction type clutches work on the principle of friction that exist between two rotating shafts whenever they connect with each other. A friction clutch uses a pressure plate, a clutch plate/disk and a release bearing to engage and disengage the flywheel and the transmission. Example of these are cone, single-plate, multi-plate, diaphragm, centrifugal and semi-centrifugal clutches.
Let us look at the different types of friction clutches in order to understand them better:
The cone clutch uses two conical surfaces to transmit torque by friction. It was the commonly used clutch type in heydays but it became replaced by the disc type wet/dry multi plate clutches. This clutch type is still in use in racing and rallying vehicles, extreme off-road vehicles as well as in powerboats.
The single-plate clutch consist of three basic parts: the engine flywheel, a clutch plate and a pressure plate. The flywheel is attached to the crankshaft of the engine and rotates with it. The clutch plate is attached to the splines of the clutch shaft and the pressure plate is bolted to the flywheel through clutch springs and is free to slide onto the clutch shaft when the clutch pedal is operated. When pushing down on the clutch pedal, the clutch is released and the pressure plate moves away from the friction disc. When releasing the pedal, the springs push the pressure plate against the clutch disc, which presses against the flywheel, which in turn locks the engine to the transmission input shaft and the clutch is again engaged.
This type of clutch works in the same manner as the single-plate clutch, with the exception that it consists of more than one clutch plate. The more the plates, the more the friction surface, the more the clutch capacity to transmit torque. For this reason, this type of clutch is used in high torque situations (such as heavy commercial vehicles, racing cars and motor cycles).
This type of clutch is similar to the single-plate clutch, with one exception: a diaphragm spring (placed between the pressure-plate and the cover pressing) is used instead of coil springs, to exert pressure on the pressure plate. Coil springs do not distribute the spring force uniformly, so the diaphragm springs addresses that problem.
Centrifugal & Semi-Centrifugal Clutches
These types of clutches make use of centrifugal force to engage the clutch. The centrifugal clutch uses shoes (similar to that on a drum brake) to act against an inner (drum-type) face in order to engage and disengage the clutch. The only difference between the two clutches is that the centrifugal clutch is fully automatic while the semi-centrifugal clutch is not. These types of clutches are widespread in the moped and biking industry.
Hydraulic torque converter
This converter is actually in principle a type of fluid coupling. It sits between the engine and the gearbox in vehicles equipped with conventional automatic transmissions and what it does is it transfers rotating power from the vehicle’s engine, to that of the transmission. It contributes to an increase in the engine’s output torque, a decrease in the output speed and at the same time, it dampens vibrations. The hydraulic torque converter can be used in manual transmissions, but mainly when it comes to extremely heavy-duty vehicles.
Image Source: https://www.klclutch.com/torque-converters/three-things-to-know-about-hydraulic-torque-converters/
Hydraulic type clutches transfer energy from one rotor to another by means of a hydraulic fluid. Examples of these are fluid couplingsand torque converters.
We can now look at the different types of hydraulic clutches:
This hydrodynamic device transmits rotating mechanical power and serves as an alternative to a semi or fully automatic mechanical clutch. In this type of clutch, there is no mechanical connection between driving and driven member. The clutch functions on the principle of liquid in centrifugal motion. The fluid coupling is not suitable for ordinary gearboxes and is used mainly in marine and industrial machine drives.
Image Source: https://kids.britannica.com/students/article/automobile/273028/197025-toc
Finally, the electromagnetic clutch deserves some attention.
In this type of clutch, the theory of magnetism is applied. The driven and driving end pieces act as separate poles of a magnet. A current activates the electromagnet and the clutch engage. The clutch disengage the moment you deactivate the electrical current. This type of clutch is prominent in the automotive industry, used in nearly every paddle-shift system. It is common opinion that if this form of clutch combines with a dual clutch transmission, it can become one of the most efficient forms of gear changing on the market.
Image Source: https://www.mayr.com/en/products/electromagnetic-clutches-and-brakes/robatic
Image Source: https://sepac.com/electromagnetic-clutches/magnetically-engaged/
How can I maintain & prolong my vehicle’s clutch life?
As a leading automotive repair and service centre, we at Steves Auto Clinic feel very strongly about vehicle maintenance. Life is valuable and a poorly maintained vehicle threatens the safety of your life every moment you or anyone else enters a poorly maintained vehicle. In the article written about the importance of having your vehicle serviced regularly, as well as the one about looking after your vehicle’s braking system, I repeatedly emphasised the importance of human safety. When it comes to maintaining your vehicle’s clutch, the status quo remains.
Due to repeated engagement and disengagement of the clutch, there is an inevitable build-up of heat due to friction. This heat has a side effect because it can introduce tiny air pockets in the hydraulic fluid that is used to transfer mechanical work and engage the clutch. These air pockets may impede overall good performance of the clutch. Bleeding the clutch to get rid of these air pockets, is certainly one of the simplest forms of clutch maintenance. It will also be wise to top up the hydraulic fluid after having bled the system.
Exactly how long your vehicle’s clutch will last before having to replace it, will depend greatly on the way you drive your vehicle and how you operate the clutch. It is equally important never to forget that the clutch plays an important role in your vehicle’s operation, it is therefore important to treat it carefully. Using your clutch gently can extend its use by thousands of kilometres. Reckless clutch operation can bring about the opposite result and cut its effective use to as much as half. You may therefore consider the following advice regarding responsible clutch operation.
The neutral is there for a reason
Are you one of those drivers who, when you approach a point where you need to stop, step on the clutch, keeping it pressed down, with your vehicle in gear ready to pull away? Do you have any idea how much unnecessary strain that exerts on the clutch? Rather place your vehicle in neutral; this will place no strain on the clutch and prolong its life.
Swift gear change
Changing gears do not need to be a prolonged exercise. When you change from one gear to another, do it swiftly. Remember, the longer the clutch pedal is kept in its downward position, the more strain is placed on the clutch. A dripping tap will eventually fill a bucket; a prolonged gear change will eventually shorten clutch life!
When you drive, be decisive. Observe your surroundings, the road and the route on which you are driving and plan beforehand when to slow down and when to exercise gear change. Abstain from too much unnecessary braking (thereby extending brake shoe/pad life) and from too frequent and unnecessary gear change (thereby extending clutch life). A pair of brake shoes/pads may be cheaper to replace than a clutch, so you may consider using your brakes to slow down rather than using the gearbox (down gearing) to slow down.
Some people leave their vehicle parked with the clutch engaged. This is not a very healthy practice because in doing so, the clutch disc stays under constant strain. Place your vehicle in neutral and engage the handbrake instead. This will have no effect on the clutch and in that way you will extend clutch life.
Ride your vehicle, not your clutch
The reference to “riding the clutch” refers simply to the tendency of some drivers to keep the clutch pedal partially pushed down. In doing so, no full engagement takes place, but what happens is that the pressure pad pushes against the clutch plate, and this causes unnecessary friction, which in turn causes unnecessary wear and tear, and we do not want that, now do we?
I think that every responsible vehicle owner can take these clutch-prolonging tips to heart. Not only does it make financial sense but it also has a positive ecological impact if you look after your vehicle’s components.
What are the most common issues with a clutch?
We now reached the core of the article. I hope that the information supplied thus far would give you a better understanding of the working of the different types of clutches available on the market and how to maintain these, whether it is by way of looking after them or by way of driving your vehicle. At Steves Auto Clinic, leader in the field of automotive repairs and servicing, we feel that it is very important that you, our valued customer, is INFORMED regarding common clutch related issues so that you may address these if ever any of them rear their little nasty heads.
What I will start with, is to remind you that with every start, with every stop and with every gear change, it means that the clutch is engaging and disengaging, and during such engaging process, friction occurs. Friction & clutch – we should see these two terms as hugging each other whenever the word “CLUTCH” is used. Friction is maybe the worst unconsciously thought of enemy in the clutch system because it brings about the wearing down of clutch components. Your clutch wears out, little by little, whenever it engage and disengage, but there is something else aggravating this process. Anything that increases the load on the clutch will also accelerate wear and tear. Here I specifically refer to practices such as towing and/or transporting something heavy, or even spinning your vehicle’s tyres.
The part suffering the most under such wear, and worth mentioning first, is the friction disk.
A slipping clutch is one of the most common clutch related concerns. When the pressure plate and the clutch disk wears down, it can cause the clutch to “slip”, causing a momentary loss of acceleration (engine racing) because the clutch does not rotate at the same speed as the flywheel. It is also possible that there is an issue in the releasing system; with the clutch linkage or with a blocked master cylinder port. It does at times happen that an incorrectly re-machined flywheel or the installation of the wrong clutch can cause a clutch to slip. If you have a slipping clutch, have a professional mechanic undertake the task of inspecting and fixing it. Amateurs should never attempt to work on such faults.
Clutch chatter (vibration)
One of the hardest working components in the clutch, is the pressure plate. It clamps the clutch disk to the flywheel and can become worn and even lose its lubrication due to a prolonged life of wear and tear. A worn pressure plate can cause “clutch chatter”, in other words, vibrations that you will feel whenever the clutch disk or clutch component is initially engaged. In another article where I discussed the brake system, I pointed out the tendency of the rotors to warp due to age and heat. The same may happen with regard to the flywheel. Over time, the flywheel can become warped or cracked due to overheating. As in the case of a worn pressure plate, the uneven flywheel can also cause this “clutch chatter”. Sometimes the fault can even be found on the driveline and not on the clutch itself. The driveline is responsible for torque transmission, and when this does not occur efficiently, clutch chatter becomes the result.
High clutch pedal release
Because the clutch disc is splined to the transmission’s input shaft, it can wear out over time. When this happens, it usually causes your clutch pedal to release higher than normal. In extreme cases, you may find that your vehicle have trouble accelerating, especially when under heavy load.
Squeaking whirring noise
If you experience an episode of “I haven’t heard that sound before”, then that may indicate that something is not as it is supposed to be. If the sound resembles a sharp whirring, rattling, or grinding noise when you depress the clutch, then it is very likely that your vehicle’s throw-out bearing is not working the way it should. Due to its continuous spinning, the throw-out bearing tend to wear out over time. When this happens, you may hear a squeaking noise as soon as you engage the clutch. This noise will not be present with the engine running and the clutch not engaged. Not only the throw-out bearing, but also the crankshaft pilot bearing can be responsible for producing this kind of noise whenever the clutch pedal reaches the floor. It is best practice to have clutch-related issues investigated and fixed.
Grinding when shifting gears
Whenever the friction or clutch disc remains engaged, the transmission input shaft keeps spinning even when you fully press the clutch pedal to the floor. Since the input shaft is still spinning, this will cause any attempt to shift gears, to result in clashing or grinding. The cause of this may be a faulty pressure plate, throw-out bearing or release mechanism. It may even be due to low fluid levels or air in the master cylinder. The clutch pedal assembly may also have too much free travel and will need adjustment.
Leaking fluid and/or strange odour
Most clutches nowadays are hydraulic and rely on hydraulic fluid for the proper functioning of the clutch. A leaking master cylinder or slave cylinder will result in the loss of hydraulic pressure. You will only be able to see such a leakage by either frequently inspecting these cylinders, by the presence of fluids pooling up under your vehicle, or even by a strange odour (when fluid leaks onto your exhaust).
Clutch pedal noise
The release mechanism can be hydraulic (most common) or mechanical. Due to lubricant drying out and the mechanism wearing down, the device is likely to become noisy because of a scraping, squealing or clunking cable, a rod or a connection. Ensure that the lubricated parts are indeed well lubricated.
Difficulty getting into/out of gear (spongy/loose pedal)
The cause of this can be due to a warped/damaged clutch plate or a problem with the master or slave cylinder. Whenever air gets into brake lines, the brake pedal will feel spongy, so make sure the clutch’s master cylinder have sufficient fluid and that the fluid is not old, in which case you need to replace it. If necessary, have the system bled and see if that rectify the issue.
Clutch pedal is hard
If the pedal is harder than usual, then the release guide can be worn and/or the release-bearing guide may have insufficient lubrication. The release mechanism should also be checked for things such as bad bushings or worn linkages, a worn release fork or pivot, a worn cross shaft guide, improper hydraulic fluid or even a damaged firewall. These may all bring about a stiff clutch pedal.
Clutch pedal stays on floor
In opposition to a stiff clutch pedal, it may happen that the pedal stay down on the floor. This may be a sign of a faulty linkage or a release bearing. Ensure that the springs in the linkage are not over-stretched and, if necessary, inspect the release bearing. It may also be that the clutch master or slave cylinder has an external seal leakage and needs replacement.
The issues highlighted here should serve as guidelines when you want to troubleshoot a clutch-related issue. What is important is to keep in mind that an ill-performing clutch is a safety issue. A qualified mechanic should inspect an improper functioning clutch; at Steves Auto Clinic branches countrywide, we not only have friendly and qualified mechanics for this purpose, but also state of the art equipment to address any related clutch issue effectively.
Sources consulted during the writing of this article: