1 513MHA-1701601 IDLER PULLEY 2 519MHA-1701822 SLEEVE-IDLER PULLEY 3 519MHA-1701804 GASKET-IDLER PULLEY 4 513MHA-1701602 AXIS-IDLER PULLEY The automobile idler gear is used to change the rotation direction of the driven gear and make it the same as the driving gear. Its function is to change the steering, not the transmission ratio.   The idler gear is located between two drive gears that are not in contact with each other.   The idler gear has a certain energy storage function, which is helpful to the stability of the system. Idler gear is widely used in machinery. It helps to connect distant shafts. It just changes the steering and cannot change the gear train transmission ratio.   The tensioning wheel is mainly composed of fixed shell, tensioning arm, wheel body, torsion spring, rolling bearing and spring shaft sleeve. It can automatically adjust the tensioning force according to the different tightness of the belt, so as to make the transmission system stable, safe and reliable.   The function of the tensioning pulley is to adjust the tightness of the timing belt. It is generally replaced with the timing belt to avoid worries. Other parts don't need to be replaced. Just go for regular maintenance. "When the engine idler gear is broken, there will be abnormal noise. At the beginning, there will be a slight rumble, and then the sound will become louder and louder after a period of time. When the sound is loud, check which wheel is damaged, because the sound of idler gear damage is the same as that of water pump and tensioner. As long as the damage of idler gear is not serious, there is nothing except noise. But if it is set all the time Ignore it, the idler bearing is completely scattered, and the belt is easy to take off. If it is a timing belt, the situation is more serious. The most serious case is the top valve. The top valve needs to repair the engine and replace the valve.