People make the decision to purchase a manually-shifted vehicle for a wide variety of reasons. For some, it's the fun or flexibility of driving a car with a clutch. However, clutch operated manually-shifted transmissions also come with some hurdles to overcome, one of which is premature wear and tear of different clutch components. In many cases, when the clutch begins to wear out, some of the moving parts will make weird sounds that are noticeable while the vehicle is idling or is in motion.
If you've noticed some sounds coming from the center portion of your vehicle, it may be contributed to a clutch that has broken or some of the individual components are wearing out. Either way, trying to troubleshoot a noisy clutch can be complex and time consuming. Noted below are a few of the common reasons why you might hear noises coming from the bell housing or the clutch department, along with a few of the best methods for troubleshooting these issues so that a professional mechanic can make repairs.
Understanding why clutch components make noise
Although the manually operated transmission has evolved considerably over the years, essentially they are still comprised with the same basic components. A clutch system begins with the flywheel which is attached at the back of the engine and is propelled by the crankshaft rotational speed. A drive plate is then attached to the flywheel and supported by a pressure plate.
As the clutch pedal is released, the drive and pressure plates slowly "slip" to apply power to the transmission gear and eventually to the drive axles. Friction between the two plates works in many ways similar to disc brakes. As you press the clutch pedal in, it engages the clutch and stops the transmission input shaft from spinning. This allows you to change gears in the manual transmission to a higher or lower gear-ratio. When you let off the pedal, the clutch disengages, and the transmission is free to spin with the engine.
There are several individual components that make up the clutch system. Operating the clutch requires having working bearings that work together to engage and disengaging (letting off on the pedal) the clutch system. There are several bearings here as well, including the throw out bearing and pilot bearing.
Some of the other parts that comprise the clutch system and can create noises as they wear include:
- The clutch master cylinder
- Clutch pedal
- Clutch release and input bearings
- Clutch pressure plate
- Clutch disc(s)
- Pilot bearing or bushing
In most cases, when the clutch is showing signs of wearing out; one or several of the above components will have broken or will be worn out prematurely. When these parts wear out, they tend to display a few warning signs that can be used to troubleshoot issues. Noted below are a few of the troubleshooting steps that need to be completed in order to determine what is causing noises coming from the clutch system.
Method 1 of 3: How to troubleshoot issues with the throw out bearing
In a modern clutch, the throw out bearing is essentially the heart of the clutch pack. When the clutch pedal is depressed (meaning it's pressed to the floor), this component moves toward the flywheel; applying the pressure plate release fingers. As the clutch pedal is released, the throw out bearing starts to release from the flywheel and engage the clutch system to begin applying pressure to the drive wheels.
Because this component is always moving in and out when you engage the clutch pedal, it makes sense to assume that if you're heading noises as you depress or release the pedal, it's probably coming from this part. In order to troubleshoot the throw out bearing, you'll have to complete the following steps without actually removing the bell housing.
Step 1: Listen for a whining sound as you press the clutch pedal to the floor. If you hear a whining or loud grinding sound coming from underneath your vehicle as you press the clutch pedal down to the floor, it may be caused by a throw out bearing that is damaged and need to be replaced.
Step 2: Listen for sounds as you release the clutch pedal. In some cases, the throw out bearing will make noises as you release the clutch. This is commonly caused by the center bearing grinding on the flywheel as it's moving towards the transmission.
If you notice this sound, have a professional mechanic inspect or replace the throw out bearing. When this component fails, it's also common that the pilot bearing may be damaged as well.
Method 2 of 3: Troubleshooting problems with the pilot bearing
For vehicles that are 4WD or rear wheel driven, a pilot bearing is used in conjunction with the vehicle's transmission to support and keep the transmission input shaft straight as the clutch applies pressure. Although this component may also be included on front wheel drive vehicles, it's typically a RWD component that works as the clutch is disengaged. As you release the clutch pedal, the pilot bearing allows the flywheel to maintain a smooth RPM while the input shaft is slowing and eventually stops. This helps reduce load on the back of the engine. When the part starts to fail, some of the common symptoms will include:
- The pilot bearing will not be able to release
- Transmission will pop out of gear
- There may be a vibration noticed in the steering wheel
Since this component is vital to the overall operation of the clutch and transmission, if not repaired, it may cause catastrophic failure. Under most circumstances, when the pilot bearing is beginning to show signs of failing, a clunking or high pitched whining sound may be present. It also causes the input shaft to become misaligned, which may also create a sound as the input shaft spins.
In order to troubleshoot whether or not this component is the source of your clutch noises, complete the following steps:
Step 1: Listen for sounds as the vehicle is accelerating after the clutch pedal is fully engaged. In most cases, when this part is failing and causing a noise, it will be as the input shaft spins; or after the clutch pedal has been fully engaged or released.
If you hear a grinding sound or noise coming from the transmission as the vehicle accelerates or decelerates while the clutch pedal is out, it may be coming from the pilot bearing.
Step 2: Try to feel steering wheel vibrations as it's accelerating. Along with the noise, you may feel a slight vibration (similar to a wheel being out of balance) as the vehicle accelerates and the clutch pedal is fully engaged. This symptom may also be an indicator of other problems; so it's best to contact a mechanic to professionally diagnose the problem if you notice.
Step 3: Smell of rotten eggs. If the clutch pilot bearing is worn out and heating up, it tends to give off a horrible smell, similar to rotten eggs. This is also common with catalytic converters, but you'll notice this more often when you first release the clutch pedal.
Any of the above troubleshooting steps can be completed by a novice DIY mechanic. In order to inspect the component for actual damage, you'll have to remove the transmission and clutch from the vehicle entirely and inspect the part of signs of damage.
Method 3 of 3: Troubleshooting problems with the clutch plates and disc(s)
The modern "clutch pack" on cars, trucks and SUV's with manual transmissions include several individual parts that work together to produce friction which in turn, applies power to drive axles after sending the power to transmission gears.
The first part of the clutch pack system is the flywheel, which is attached to the back of the engine. On an automatic transmission, the torque converter acts in similar function as the manual clutch. However, its parts are a series of hydraulic lines, and turbine rotors that apply the pressure.
The clutch disc is connected to the back of the flywheel. Then the pressure plate is applied on top of the clutch disc and adjusted by the automotive manufacturer to permit a determined amount of pressure to be applied as the clutch pedal is released. A lightweight housing or cover is then applied to the clutch pack, which keeps dust produced by the burning of clutch discs from spreading into other engine or transmission components.
Sometimes this clutch pack becomes worn out and will need to be replaced. In most production vehicles, the clutch disc is the first to wear, followed by the pressure plate. If the clutch plate is wearing out prematurely, it will also exhibit a few warning sign which may include sounds, noises and even smells similar to the pilot bearing.
If you suspect that the noises are coming from your clutch pack, complete the following tests to determine if this is the case.
Step 1: Listen to the engine RPM as you release the clutch pedal. If the clutch disc is worn out, it will create more friction than it should. This tends to cause the engine RPM to rise as opposed to lowering as the clutch pedal is depressed.
If the engine sounds "weird" while you're releasing the clutch pedal, the most likely source is the clutch disc or the pressure plate that has worn out and needs to be replaced by a professional mechanic.
Step 2: Smell for excessive clutch dust. When the clutch disc or pressure plate is worn out, you'll smell a lot of clutch dust coming from below your vehicle. Clutch dust smells like brake dust, but has a very pungent odor.
It's also very possible that you'll see excessive dust coming from the top of your engine or what appears to be black smoke if the disc is damaged enough.
The parts that comprise the clutch pack are high wear components and need to be replaced on a regular basis. However, the frequency of replacement will depend on your driving style and habits. When replacing the clutch, it's also very common to have the flywheel resurfaced. This is a job that should be completed by a professional mechanic as clutch adjustment and replacement requires specialized tools and skills that are often taught during technical school or ASE certification training.
In most circumstances, when you notice noise coming from the vehicle as you release or depress the clutch pedal, it's a sign of damage to one of the multiple internal components that make up the clutch pack and clutch system. It may also be caused by other mechanical problems with the transmission such as worn out transmission gears, low transmission fluid or a hydraulic line failure.
Anytime you notice this type of sound coming from below your vehicle, it's a good idea to contact a professional mechanic as soon as possible to complete a loud noise while using the clutch inspection. A mechanic will inspect your clutch operation in order to verify the noise and determine the correct course of action. A test drive may be necessary to duplicate the noise. Once the mechanic has ascertained the cause of the problem, the right repairs can be suggested, a price will be quoted and the service can be completed on your schedule.
A damaged clutch is not only an inconvenience, but it can lead to additional engine and transmission component failure if not repaired as soon as possible. Although in most cases, noises from the clutch are a sign of damaged or worn out parts, finding and replacing these parts before they completely break can save you a lot of money, time and frustration. Contact a professional mechanic to complete this inspection or ask them to rebuild the clutch on your car.
This article originally appeared on YourMechanic.com as How to Troubleshoot a Car With Clutch Noise and was authored by Tim Charlet.