>How to recognise and check for clutch problems
How to recognise and check for clutch problems
In a manual transmission car, the clutch is the connection between the engine and gearbox, and therefore the wheels. If the clutch is slipping and not doing its job; transferring power to the drivetrain, the car cannot be driven.
There are other ways a clutch can start to fail, including problems with bearings, hydraulics and more. Read on to learn all there is about clutch faults, slave cylinder problems and how to recognise the symptoms of a failing clutch before it’s too late and you have to bear the cost of a replacement clutch.
What is a clutch?
In mechanical engineering terms, a clutch is any device that transfers power from a source to a transmission or drivetrain. In a car, it connects the engine to the gearbox, enabling the car to drive.
It’s composed of a few different parts and often differs between cars. The one constant are three components called the ‘pressure plate’, ‘flywheel’ and ‘friction plate’. There also needs to be a system to actuate it.
For more information about how clutches in manual and automatic cars work, check out our article here.
How long does a clutch last?
Generally, clutches will last upwards of 80,000 miles provided the car has been well cared for and its drivers have been sensible. The way you drive can have an impact on how long a clutch lasts.
What are common clutch faults?
Due to the complexity of the system, there are a few ways in which the clutch can fail.
Worn out or slipping clutch plate
Integral to any clutch is a friction surface, similar to a brake pad, but working in the opposite way, the clutch plate is forced against the engine's flywheel to transfer power to the drivetrain.
Just like when a brake pad wears out, if the friction material has been worn away, the clutch plate will not grip the flywheel properly and will slip.
Symptoms of a worn clutch:
- Engine revs increase without the car accelerating, particularly on hills
- The bite point on the clutch pedal is very high
- Gears are difficult to select
- Gearbox crunches or jolts when a gear is selected
When to fix a worn clutch
Depending on your driving style, the signs of a worn clutch become apparent quite a long time before the clutch will need replacing. If you are noticing the clutch slipping in normal use, i.e. when accelerating on flat ground with little load, the clutch needs to be replaced.
A high clutch pedal can indicate the clutch plate is wearing out, but in some cars, it can mean the clutch just needs adjusting. It’s best to take the car to a trusted garage and get them to check.
If you leave a slipping clutch too long, the bolts in the clutch plate can start to contact the flywheel. This will require a new flywheel, which can easily double the cost of a clutch repair.
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Clutch throwout bearing
Because the clutch plate is spinning, but still needs to be pressed against the flywheel, a bearing is used on the end of a lever. The lever is often referred to as the clutch fork, and the bearing is a ‘Throwout bearing’.
Through normal usage, bearings wear out, instead of a silent smooth operation, the surfaces become worn and make noise when spinning. The throwout bearing is no different, but it will only make a noise when the clutch pedal is pressed.
Symptoms of a bad clutch throwout bearing
- Whining or scraping noise when the clutch pedal is depressed
- No noise when the clutch is engaged (with pedal not depressed)
- Rumbling feeling through the clutch pedal
When to change a bad throwout bearing
Replacement clutch bearings can cost in the region of £300-£600. It is usually better to change the clutch plate too, and vice versa.
This is because most of the work is involved in removing the gearbox, once that’s off, changing the clutch plate too will only add £50 or so, and will remove the need to pay to remove the gearbox again in the future.
Clutch master cylinder fault
It takes considerable force to operate the clutch fork and disengage the clutch plate from the flywheel. To enable a person to do this easily, a hydraulic system is used.
The clutch pedal is attached to the master cylinder, this creates pressure in the oil lines, operating the slave cylinder, in a similar way to a car's brakes.
For this hydraulic system to work effectively, there are many seals in both the slave and master cylinders, that need to withstand the high-pressure oil. If one of these fails, the clutch will not operate.
Bad clutch slave cylinder symptoms
- Very heavy or light clutch pedal
- Ineffective clutch pedal
- Oil dripping from under the car
- Hydraulic oil level low (often shared with brake fluid)
- The clutch pedal sticking at bottom of the travel
When to fix a clutch master cylinder
Symptoms of a bad slave cylinder can come on suddenly and give very little notice. This means it’s imperative to get any issues looked at straight away, as they could render the car immobile quite easily.
Typical repair costs for clutch hydraulics depend heavily on which cylinder is at fault. Because the slave cylinder is inside the clutch housing, it requires the gearbox to be removed.
It’s therefore recommended that you change the clutch plate as well as the slave cylinder, which in total could run between £400-500.
Clutch rattles and juddering
There are a few components inside the clutch system that could cause a rattling sound, from the main clutch bearing to a loose clutch fork, they are quite difficult to diagnose without removing the gearbox and inspecting.
Some cases of rattling can be caused by a fault DMF or Dual Mass Flywheel, more commonly found on diesel-engined vehicles, these can cause a knocking sound as well as a vibrating feel through the clutch pedal.
When to call an expert
An issue with your clutch can easily ruin your day by rendering your car immobile. If any of the above-mentioned symptoms are present it’s best to get the car inspected as soon as possible.
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