For decades, drive belts, V-belts, multi-vee-belts, and serpentine belts have already been used to transmit power from the engine crankshaft pulley to components, like the power steering pump, air conditioning compressor, water pump, or cooling fans. Toothed timing belts and timing chains, too, are accustomed to transmit power from the crankshaft to the camshafts, and 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 lengthy, if at all, with incorrect tension. A loose drive belt won’t drive the accessory reliably, slipping and making sound. Conversely, an excessively limited belt may cause item or pulley bearing harm. Various kinds of tensioner pulley preserve long-term engine and item quietness and Car Pulley Belt reliability.
Tightening or Loosening
Sometimes, maintenance or restoration will require tightening or loosening a tensioner pulley. Changing a drive belt or timing belt, for instance, would need you to loosen a tensioner pulley to create room for the brand new belt, as the brand new belt is smaller sized than the worn drive belt.
You will have to tighten a tensioner pulley, generally, after the installing 
a fresh drive belt, or to adapt 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 using a special tool-always use the special tool to prevent 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 an alternator, and NAI tensioners as adjustable idler pulleys. There are three types of tensioner pulleys and many methods to loosen them.
Mechanical tensioner pulleys will be the simplest, many common, and least susceptible to failure. There is usually one caveat, nevertheless, as mechanical tensioner pulleys require manual adjustment. This makes them prone to user error, leading to insufficient or extreme belt pressure. Additionally, they need to be adjusted to compensate for belt stretch over time.