For many years, drive belts, V-belts, multi-vee-belts, and serpentine belts have 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 used 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 well, or for lengthy, if at all, with incorrect tension. A loose drive belt won’t drive the accessory reliably, slipping and producing noise. Conversely, an excessively limited belt may cause accessory or pulley bearing harm. Various forms of Car Pulley Belt tensioner pulley keep long-term engine and item quietness and reliability.
Tightening or Loosening
Sometimes, maintenance or restoration will demand tightening or loosening a tensioner pulley. Replacing a drive belt or timing belt, for example, would require you to loosen a tensioner pulley to create room for the brand new belt, as the 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 modify for a stretched drive belt that hasn’t worn enough to warrant replacement. Stretch out belts don’t need tensioner pulleys but are “stretched” into place using a special tool-always utilize the special tool to prevent belt damage.
Tensioner pulleys generally fall into two categories: accessory-integrated (AI) and non-accessory-integrated (NAI). Think of AI tensioners as adjustable add-ons, 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 prone 
to failure. There can be one caveat, nevertheless, as mechanical tensioner pulleys need manual adjustment. This makes them prone to user error, leading to insufficient or extreme belt stress. Additionally, they have to be adjusted to compensate for belt stretch as time passes.