Car flywheels: problems, symptoms and repairs

Car flywheels: problems, symptoms and repairs

What is a flywheel? What does it do?

A flywheel is a bulky clutch component which is shaped like a large disc. It is attached to the crankshaft of the engine and its primary purpose is to ensure that the power from the motor is transferred smoothly. It neutralises crankshaft vibrations and balances fluctuations in engine speed, storing excess energy for later use. This energy is used to keep the engine running when the driver takes their foot off the accelerator pedal, for example.

These components connect the engine to the transmission in manual vehicles, using the clutch to transfer power to the wheels. Moreover, if the flywheel is damaged, it will be much more difficult to successfully change gears and could cause irreversible damage to the clutch. It is therefore critical that the problem is diagnosed and fixed as soon as possible.

Component types

These discs are usually made from steel, cast iron, or aluminium. The higher the rotational inertia of the disc, the more effectively it prevents high fluctuations in speed. There are two main types of flywheel: single mass flywheels and dual mass flywheels.

 Single mass flywheels: 

These consist of a single metal disc that does not include any moving pieces, reducing the complexity of the unit and making it easier to maintain. These components are highly resistant to heat and warping, and can be resurfaced if necessary. As well as being durable, they are much less expensive than dual units. On the other hand, one-piece components provide less protection against vibrations and are known for being noisy. They are more suitable for high-speed vehicles, such as those for racing, and off-road driving.

 Dual mass flywheels: 
Dual mass flywheel

As you can probably guess, these flywheels consist of two discs. One is connected to the clutch and the other is attached to the crankshaft. In addition to this, they include springs which dampen torsional vibrations. They are thereby designed to protect the engine and transmission components more efficiently. They may also improve fuel efficiency as allow the engine to be used more effectively. These are usually installed on large, heavy vehicles with diesel engines. The downside is that they cannot be resurfaced and are more susceptible to thermal damage.

What causes flywheel damage?

There are several factors that contribute to premature wear and failure. Here are some of the most common causes:

  • i Improper maintenance. If components such as a new starter or clutch are not installed properly, other parts could get damaged or become misaligned. To add to this point, if the clutch gets damaged, it is highly advisable to get it replaced as soon as possible. If you leave it, it will affect the flywheel, and clutches are much easier and cheaper to replace.
  • i Engine condition and driving habits. For example, it could be caused by rough engine starts, heavy loads, driving in the wrong gear, and slow cranking speeds.
  • i Overheating. This can be deadly for the discs as they can crack or warp, and it is often caused by a slipping clutch.

Symptoms of a faulty flywheel

Symptoms of a faulty flywheel
  • ! A burning smell. Drivers will often notice a burning smell coming from underneath the vehicle. This is an indicator that the clutch isn’t working or being used properly and the flywheel could be the culprit. For example, if the flywheel is warped, the clutch plate will slip and wear away, causing a burning smell. If the problem is not rectified, the clutch may eventually stop working altogether.
  • ! Difficulty changing gears. A damaged flywheel will make it much more difficult to change gears as the clutch plate may not disengage properly. Cracked flywheel discs are more likely to warp, causing clutch and transmission problems.
  • ! A vibrating clutch pedal. If the clutch pedal is vibrating this could be a sign that the flywheel spring mounts are bad. This could be caused by a crack or worn disc. The spring is there to neutralise vibrations when the clutch is engaged.
  • ! Clutch chatter. There are a large number of causes for this, but the clutch chatters when it “skips” on the flywheel while it is engaged. This sound may be due to a glazed or distorted clutch disc, but may also be caused by missing or damaged flywheel dowel pins.

Can you drive with a faulty flywheel?

It is possible to drive with a bad flywheel if the damage is minor. However, this does not mean that it is advisable to do so. The fault could lead to more serious damage affecting the clutch components, crankshaft, and engine itself. You will feel more engine vibrations and it will affect its overall performance. In addition, if you suspect clutch damage, you should have the vehicle inspected by a professional as soon as possible.

Is it possible to have it repaired?

Is it possible to have flywheels repaired

Single mass flywheels are easier to repair because the surface of the components can be restored, whereas dual mass wheels usually require a replacement as grinding processes can affect the internal components. This is where things can start to get expensive as it is often necessary to replace the clutch at the same time as the flywheel. Thankfully, there are plenty of affordable clutch kits out there on the market.


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