Fault in the dual-mass flywheel, what are the symptoms?

spot a faulty dual mass flywheel It is not difficult if you know what it is for and how it works. This piece is also called a dual-mass clutch and is an element that absorbs the vibrations of the engine. In this way it protects the rest of the components and allows the car to have a smooth and comfortable operation. Once we have this clear, it is easy to assume that when the dual mass stops working correctly, the symptoms that we will notice will be excessive vibrations and rattles.

So that you can know if the dual-mass flywheel is failing, we are going to describe a series of symptoms that can clear your doubts when making your own diagnosis. And what is more important, we are also going to tell you what symptoms can mislead you and end up making mistakes.

What are the symptoms of a dual-mass flywheel failure?

A symptom of a failed dual-mass flywheel is a noise when depressing the clutch with the engine running in neutral and the car stopped. A noise like a metallic "ratchet" would indicate a fault in the dual-mass or with a bit of luck only in other elements of the clutch (collar, etc.)

Another quite obvious symptom is when, when stopping the engine with the ignition key, a "clack-clack-clack" is heard coming from the compartment at the instant it is stopping.

Un slightly faulty dual-mass flywheel will produce a humming noise and vibrations that will be broadcast throughout the powertrain. They can be noticed especially in the area of ​​the pedals, but also on the steering wheel, seat, etc To isolate these vibrations from the dual mass from other possible failures, we must test the car in neutral. At idle the vibrations will be large and will decrease in intensity but increase in frequency as the engine accelerates.

Anyway, a dual-mass flywheel can be 100% diagnosed once disassembled. It is expensive and you will have to pay labor, but if the mechanic is trustworthy, that is better than not paying directly for such an expensive part. To make it clearer, we are going to see each of the symptoms of failure in the dual-mass flywheel in more depth.

Vibration and rattling noise at idle

When a flywheel dual-mass stops fulfilling its function, vibrations and noises increase considerably in the vehicle. Put the car in neutral and see if you notice these symptoms. To make sure it is the dual mass and not another element of the engine, you can accelerate little by little. If, as the revolutions rise, the vibrations decrease in intensity but increase in frequency, it is very possible that the origin is the dual-mass flywheel.

Another way to make sure is to step on clutch with the car idling. If the metallic chatter disappears when you do this, it is most likely the dual-mass flywheel.

Mechanical explanation:

Y…  what is bimasa used for? Contrary to what one might think, the motor does not rotate continuously and smoothly. As is logical, by obtaining its turning force from the explosions generated in its cylinders, in the same turn there is a moment in which it goes faster because the explosion has taken place and another that goes slower until the next one does not take place. detonation. East pulse-based operation generated by explosions is reflected in what we perceive as vibrations, because a motor rotates several thousand times per minute, as you can see from the rev counter.

all these vibes they would pass to the rest of the components and the passenger compartment if it were not for the dual-mass flywheel. Unlike a single mass flywheel, which is simply a disc that connects the engine to the clutch, the dual-mass flywheel is made up of two discs with a spring system that absorb vibrations from the engine. While the first disc is connected to the motor and receives the vibrations, the second only receives a fraction of them thanks to the springs that separate them.

If the dual-mass flywheel is sufficiently worn or deteriorated, the spring system that absorbs the vibrations between its two discs retains nothing or almost nothing. This causes noise caused by discs, which move too much one with respect to the other, because they are not properly retained by the spring system.

Vibrations when putting the foot on the clutch

The clutch pedal can also give you a clue to a faulty dual-mass flywheel. Moreover, through him you can even determine to what extent it is deteriorated. Of course, not all cars are the same and there are brands in which it is more noticeable and others in which it is less. This depends on what components you use and how you assemble them. Even so, the following symptoms are the most frequent and can help you determine what is happening in your car.

A slightly damaged dual-mass flywheel will cause vibrations that will reach the clutch pedal through the entire powertrain. These vibrations can also be felt in the steering wheel, seat and dashboard, but where they should be most noticeable is in the pedal. If this vibration is not accompanied by a metallic sound while idling, this may mean that the dual-mass flywheel is not completely damaged and that, although it does not absorb completely  vibrations, yes it does at least in part.

Mechanical explanation: this is because the spring system is somewhat worn or damaged and cannot absorb vibrations effectively. There is no rattling sound coming from the dual mass flywheel because the springs are still partially working and the flywheels still don't move as if they were loose.

Knocking when turning off the engine

Another quite illuminating symptom of a fault in the dual-mass flywheel is when, when turning off the engine with the ignition key, a “clack-clack-clack” is heard coming from the engine compartment in the moments that the engine stops.

mechanical explanation: the sound of a damaged dual-mass flywheel It becomes more apparent when you drop the revs a lot.. This is why it sounds when the engine is idling and why it sounds even louder when the engine is stopping.

Tremors when starting the march

You will normally notice this together with the rest of the symptoms that we have described. If it occurs on its own, this may mean that the dual mass flywheel is somewhat worn and is capable of absorbing vibrations at idle, but is not able to absorb them when they increase.

Mechanical explanation: when starting the march (put first and release the clutch as we accelerate) the revolutions are still low and the force used is higher because the motor is starting to push. This requires more work to the dual mass, which is not capable of absorbing them with the consequent tremor in the car.

Tips to take care of the dual-mass flywheel

Either because you suspect that it is a little worn or because even though it is new you want it to last a long time, there are a series of habits that you can acquire to avoid a dual-mass flywheel failure before its time.

Don't go full throttle when you're at low revs.

Note that When the dual-mass flywheel works the most, it is with low revolutions but a lot of torque.. That is, when we accelerate a lot at low revs. This is what we do when we go up a hill in high gears or when, to save fuel, we go full throttle to gain speed without changing gear.

A good sign that we are not doing it right is when, even when it is new, some uncomfortable vibrations when accelerating at low revs. Change to a shorter one and everything will be fine. However, even if the car does not warn you with vibrations, you should know that the work of the dual mass will always be greater if you accelerate down a hill at 1.500 rpm instead of 2.000 rpm.

Rescheduling can speed up your attrition

When we reprogram the control unit of a car to gain power and torque, we are making the engine work harder without adapting the rest of the components. Although these modifications do not have to go beyond the reasonable limits of the car's mechanics, they will accentuate the wear they receive.

Do not release the clutch suddenly

Although this is obvious, because not only the dual-mass flywheel suffers but also the clutch, the engine and other parts, it is another cause of early deterioration of the flywheel. Release the clutch smoothly and at the right time. You should not fall into the mistake of releasing it too late, when the engine revolutions have already dropped too much, making the clutch work to recover them. In the following video you can see how to do it in such a way that you extend the life of the clutch:

The dual-mass flywheel can also be damaged by a clutch overheating (causing him to skid unnecessarily) or for having clutch disc too tight, to the point that the rivets on the lining rub against the bi-mass or from slipping so much they abrade the surface.

So one last piece of advice: if we notice something strange in the clutch, maybe we should have it checked. A good diagnosis in time can save us the replacement of the bimass, if for example, we damaged the dual mass for not changing the clutch disc on time.

How much can a dual-mass flywheel breakdown cost me?

A breakdown in the dual-mass flywheel is very expensive, since it can rarely be repaired and garages simply change the whole set. We are talking approximately 600 euros for the dual-mass flywheel, plus another 200 euros for the clutch, plus another 250 euros for labor. Obviously these figures can vary quite a bit from one car to another. Total, we will be lucky if it falls below 1.000 euros.

Images – Photo 3 by 3ndymion _, CC BY-SA ; Photo 4 by srgpicker, CC BY; Photo 5 by Timitrius, CC BY-SA ; Photo 6 by Tony Harrison, CC BY-SA