How to Adjust an Idler Pulley

Being able to adjust an idler pulley is an important part of vehicle maintenance, and it is a task that any average car owner can accomplish, with a few tools and a spare hour or two. Of course, every type of vehicle is designed a little differently, so adjusting the idler pulley may be a little different on your particular car or truck, but the steps below are basic directions for most vehicles. Some vehicles also have self adjusting screws, which may change the bolts, and how many bolts have to be loosened in order to adjust the tension. Once again, depending upon the make and model of your vehicle, different sized tools will be needed. Have a complete kit at your side, so that you do not have to search for the exact socket or wrench.

Materials and Tools You'll Need:

  • Socket set
  • Wrench set
  • Screwdriver set
  • Pry bar

Step 1: Loosen the Idler Pulley

Locate the center belt on the idler pulley. Fit the correct size wrench or socket onto it, and loosen it up so that the pulley has some play. Next, find the adjustment bolt, which is usually on the lower right hand side of the pulley, and loosen it up. Do not take the bolt completely out, just loosen it up enough to allow the pulley the ability to move.

Step 2: Adjust the Idler Pulley

Place the pry bar into a space between the pulley and a solid section of the motor, and slowly push down onto the bar, until the idler pulley is pulling the belt tight. Never over tighten this pulley, or the belt will snap when you are driving down the road. Basically, judge the correct tightness by using 1 finger, and pressing the belt down slightly. You should have a small amount of play in the belt, usually between 1/16 and 1/8 of an inch.

Step 3: Tighten the Idler Pulley

Retighten the bolts that you previously loosened, beginning with the adjusting bolt first. Tighten down to the torque that is recommended in the manual, made specifically for your vehicle. Never guess on the tightness of a bolt, spend the extra money and buy a good torque wrench, and follow the specifications that are given for your vehicle.

This is the basic steps in adjusting an idler pulley upon any type of car or truck. Some newer models have a self adjusting spring built into them, so after you tighten the idler pulley down, the automatic adjustment should make the belt as tight as recommended by the manufacturer.

Just take care not to bend the spring, or attaching linkage, in any way. If you have to loosen the spring in order to adjust the tension, be sure to tighten it back down to the exact torque that it was before you touched it. Vehicle parts are all designed to work in unison, so if the exact specifications of the company are not followed, then your vehicle parts might not work in tandem with each other.