An idler wheel keeps a belt or chain taut and away from obstructions. Most are made of plastic or aluminum and rarely require maintenance. The tensioner bracket is responsible for maintaining the integrity of the serpentine belt system, and the idler wheel needs to be replaced when it starts to get noisy.
An idler wheel is used to keep a belt slack on an engine or machine. When routing a belt, you need an idler to pull the belt away from any obstructions and put pressure on the belt to keep it taut. The same principle is applied to chain applications, where the idler typically has a sprocket-like appearance. Commonly made of plastic or aluminum molded around a bearing, the idler runs smoothly and quietly, rarely requiring specialized maintenance. A squeaking or grinding sound indicates that the idler wheel needs to be replaced.
Most idlers are mounted on a spring loaded bracket which allows the idler to be pulled off the belt to remove the belt. Once the new belt has been placed around all the pulleys, the idler can be released to go against the belt. The spring clip maintains pressure against the belt and prevents the belt from jumping off the pulleys. This is especially important on a serpentine belt system.
A serpentine belt is a single rubber belt that drives all of an automobile’s engine accessories. The serpentine belt is typically ribbed and runs on pulleys that have several grooves. The belt is wound around the pulleys such that the idler typically rides against the smooth back side of the belt. This arrangement ensures that the tensioner does not damage the grooves on the belt.
The only adjustable component in the typical serpentine belt system is the tensioner bracket, and this single component is responsible for maintaining the integrity of the entire system. Occasionally, this spring loaded mounting bracket gets stuck in place or the spring breaks. The result of a broken spring is often a squeaky belt. The belt will squeak as it slides over the pulleys due to lack of tension. Automobile belts should be checked for wear every 50,000 miles (80467.2 km) and tensioner components should also be checked at that time.
The bearing in an idler wheel typically cannot be greased. When it starts to get noisy, it needs to be replaced. Most idlers are replaceable by simply removing the retaining nut and sliding the old pulley off the shaft. The new pulley can be slid back onto the shaft and tightened. Once the serpentine belt has been placed back on the pulleys, the system is ready for use.
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