Repairing a slipping clutch
By Hayden Featherstonhaugh
Firstly, let me explain what a clutch is and what it does. The clutch is a mechanical unit which is placed between the vehicle’s engine and the manual transmission. It connects and releases the engine to the transmission.
Click this link to the Exedy Australia website for a simple video that shows how it operates
The Clutch itself is made of three main components from left to right:
1- The release bearing
2- The clutch pressure plate (or often called cover)
3- The clutch plate
The other component vital to the clutch operation is the engine flywheel
The clutch plate has a brake pad-like material which makes up the large flat surfaces. It is clamped between the pressure plate and the flywheel using spring tension which comes from a diaphragm spring inside the clutch pressure plate. Over time this material wears.
How does it wear?
Each time you take off from a standstill, be it either in a forward or reverse gear, you get a small amount of slipping. Think of a new learner driver revving the engine and not moving far or fast. You will smell a horrible burning smell, sometimes even see smoke from under the body or bonnet when extreme slipping is performed. Over time this small amount of normal slipping will wear down the material until it wears away to the mounting rivets (the small silver discs seen on the clutch plate in picture). When the clutch material reaches this point the clutch plate will usually start to slip by itself when the car is accelerating at normal speeds. This in turn exaggerates the wear process even faster which will cause hot spots and heat cracks on the flywheel further accelerating the wear process and feel of the clutch pedal under foot will change. The point at which the clutch pedal take-up point will move as the clutch wears (depending type of clutch it can move up or down. Pull type or push type. For this article it doesn’t matter what type your car has). This is usually a sign that the clutch unit is worn. Another factor that cannot be overlooked when assessing the clutch wear is the engagement procedure. The release bearing can be cable or hydraulically operated. Hydraulic fluid leaks will change the pedal take-up point height as will a stretched clutch cable. Virtually all modern cars use hydraulic actuation as it gives a much better and consistent feel without the need to continually adjust the clutch pedal as the cable stretches.
Hotspots and heat cracks shown here are on the flywheels of clutches that have had excessive slipping
If a clutch is continually driven on until it no longer can maintain any fiction with the flywheel and pressure plate it will become excessively hot and eventually leading to the clutch plate disintegrating as shown in these pictures.
How do you diagnose a slipping clutch? How do you know if it’s worn? How do you tell if it is a hydraulic or a cable operated clutch? How do you know if it’s a hydraulic problem?
Does your vehicle rev excessively when accelerating normally? Does your fuel consumption seem to be high? Do you get a burning smell or smoke when driving? Does the clutch pedal feel heavy or does the clutch pedal take-up point seem extra high or very close to the floor? These are all signs that shouldn’t be ignored. There may be something that needs attention with your clutch. Here at The Service Depot Unit we can help with the diagnosis and repair of a clutch issue. We can perform clutch hydraulic repairs, clutch replacements for all makes and models. We can perform a clutch kit upgrade for a performance or modified vehicles. Heavy-duty kits for towing, off road or track use are also specialty of ours. Don’t let that slipping clutch ruin a great road trip, beach holiday or track day. We use only trusted brands like Exedy, Clutch Industries, Valeo, Sachs, Luk and Clutch Pro. Don’t delay call today.
The Service Depot
Unit 15 Eureka Centre, 29 Moreton Bay Road
Capalaba (07)3169 2333
Caring for your car