This component is one of the important and consumable parts in a car engine. It consists of a bearing and a plastic roller on which the timing belt runs. It is usually replaced during timing belt service or replacement. Failure of this component can cause serious engine damage, leading to timing belt breakage and ultimately bent valves.
Premature failure of the roller may be caused by the entry of dust or water, or by engine oil leakage into the timing belt cover. The first sign of roller failure is usually noise, especially in cold weather. Therefore, it is recommended to purchase and replace the timing belt kit as a complete set.