Belt Tensioner
To ensure that the timing belt is operating at optimum tension at all times, a belt tensioner is needed. This rotating pulley prevents the belt from becoming slack and operating inefficiently or incorrectly. The tensioner may have to be adjusted manually during fitting though many, known as automatic tensioners, have springs which automatically adjust the tension.
Belt tensionersfor any car are an integral part of timing belt operation and should be replaced if wear and tear is spotted to prevent damage to the belt.

Drive Belt Idlers
The drive belt, or fan belt, provides power to ancillary systems within the car, such as the alternator, air conditioning and power steering.
Drive belt idlersare required to prevent it from becoming loose and moving irregularly. These idler pulleys are an essential part of the setup.
Each drive belt idler can become worn over time, becoming noisy and eventually producing a negative effect upon the drive belt. When replacing the drive belt it may also be necessary to replace the idler pulleys.