Dual mass flywheels are ingenious and increasingly important parts of modern, high-compression, diesel engines. These flywheels eliminate jumps in the torque of an engine by smoothing out the power from the pistons. How and why do these jumps occur? Well, pistons must compress air that is forced into their chambers and, in doing so, they slow down. But, when the engine fires, the combustion of fuel causes these same pistons to surge forward. This inevitable process of slowing down and surging forward repeats itself over and over again, causing the engine to rock back and forth on its mounts. The vibration and movement in the engine will increase along with the weight of the load the engine is trying to move (in other words, the torque that is being applied). Dual mass flywheels should smooth this severe oscillation, but, occasionally these flywheels go bad. When this happens, the automobile will begin to shake or vibrate. If this occurs, read the following article for a few ideas about what might be wrong.
Check or Replace the Dampener Springs
Dual mass flywheels utilize dampener springs to keep the resonant vibrational frequencies of an engine down. However, these springs along with their nylon retainers, may break or simply fail if other parts of the engine are not running smoothly. Ideally, these springs should only be compensating for an engine’s vibration while the engine is running in low gear and at a low level of rounds per minute. However, faulty engine valves and fuel injectors, amongst other things, can cause an increase in engine vibration. This, in turn, causes the dampener springs to work harder and more often to compensate. Check the springs first; if they are broken, look for other engine problems before replacing them.
Check the Friction Ring
Every dual mass flywheel has a friction wheel between its inner and outer portions that allow them to spin easily over each other. This ring will often wear out or break if the torque of an engine exceeds the amount an engine can handle. This usually happens when a car or truck is forced to carry loads that are too heavy. Tell-tale signs that an automobile is being pushed passed its capability are heat cracks and burn spots. Look for these on the friction ring, as well as on the pressure plate.
Examine the Center Bearing Inside the Flywheel
If the dowel pins of the flywheel are misaligned with the pressure plate, the resulting vibration can damage the center bearing which carries the load between the two portions of the flywheel. The center bearing should also be supported by the transmission input shaft. If the pilot bearing fails, it will destroy this input shaft which will, in turn, fail to support the center bearing causing it to malfunction as well. Furthermore, once the input shaft has been repaired, one must ensure that it is installed and aligned properly, or as before the center bearing will not last very long.