For many years, drive belts, V-belts, multi-vee-belts, and serpentine belts have already been used to transmit power from the engine crankshaft pulley to components, such as the power steering pump, air-con compressor, water pump, or cooling fans. Toothed timing belts and timing 
chains, too, are accustomed to transmit power from the crankshaft to the camshafts, plus some from the camshaft to camshaft, depending on engine design.
The drive belt, timing belt, or timing chain will not work very well, or for very long, if at all, with incorrect tension. A loose drive belt won’t drive the item reliably, slipping and producing noise. Conversely, an excessively limited belt may cause accessory or pulley bearing harm. Car Pulley Belt Various types of tensioner pulley keep long-term engine and item quietness and reliability.
Tightening or Loosening
Sometimes, maintenance or restoration will require tightening or loosening a tensioner pulley. Changing a drive belt or timing belt, for example, would need you to loosen a tensioner pulley to create room for the brand new belt, as the brand new belt is smaller than the worn drive belt.
You will have to tighten a tensioner pulley, in most cases, after the installation of a fresh drive belt, or to modify for a stretched drive belt that hasn’t worn enough to warrant replacement. Extend belts don’t require tensioner pulleys but are “stretched” into place utilizing a special tool-always use the special tool to avoid belt damage.
Tensioner pulleys generally fall into two classes: accessory-integrated (AI) and non-accessory-integrated (NAI). Think about AI tensioners as adjustable components, such as for example an alternator, and NAI tensioners as adjustable idler pulleys. There are three types of tensioner pulleys and many ways to loosen them.
Mechanical tensioner pulleys will be the simplest, most common, and least prone to failure. There is certainly one caveat, nevertheless, as mechanical tensioner pulleys require manual adjustment. This makes them susceptible to user error, leading to insufficient or extreme belt tension. Additionally, they have to be adjusted to pay for belt stretch as time passes.