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 add-ons, like 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, 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 very long, if at all, with incorrect tension. A loose drive belt won’t drive the accessory reliably, slipping and producing noise. Conversely, an excessively tight belt may cause accessory or pulley bearing harm. Various forms of tensioner pulley maintain long-term engine and accessory 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 instance, would require you to loosen a tensioner pulley to create room for the brand new belt, as the new belt is smaller sized compared to the worn drive belt.
You’ll need to tighten a tensioner pulley, in most cases, after the installing a new drive belt, or even to change 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 utilize 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 accessories, such as an alternator, and NAI tensioners as adjustable idler pulleys. There are three types of tensioner pulleys and Car Pulley Belt several 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 tension. Additionally, they have to be adjusted to pay for belt stretch over time.