Below is generic information for most modern-day vehicles:Serpentine belt tension is set by the tensioner assembly, which consists of the spring tensioner and an idler pulley. Ideally, the tensioner assembly should be replaced when the serpentine belt is changed. In many cases, this is not the most cost-effective solution. Most people will replace the idler pulley, which costs about 25% of what the tensioner assembly costs. For the more frugal, or more performance-oriented individual, repacking the idler pulley bearing is an option. Since space is normally tight on this side of the engine, access may be improved by moving the power steering reservoir aside or by removing the appropriate wheel and plastic wheel-well liner. Here’s how to repack the bearing:1. Remove idler pulley from tensioner, normally by using a 15 mm combination wrench.2. Examine old bearing and ensure it’s serviceable.3. Remove bearing grease seals, using a small screwdriver, and soak bearing and pulley in kerosene. Ensure bearing is clean of all old grease and dirt.4. Inspect ball bearings, cage, and race for any signs of damage.5. Allow bearing to dry. Compressed air can be used but don’t try to spin the bearing or it could be damaged.6. Pack bearing with grease, thoroughly forcing grease into all crevices of the bearing. Approximately 25% of the inside space of the bearing should be filled with grease. I recommend using either Mobil 1 Synthetic Universal Grease, NLGI #2, or Amsoil Synthetic Multi-Purpose Grease, NLGI #2. 7. Remove excess grease and replace both grease seals.8. Button things up.The bearing should now be as good as, or better than, new. Goodyear recommends tightening the 15 mm mounting bolt 35 to 40 lb.-ft., on a standard NTN 6203 bearing, with a 17 mm inside diameter. This common bearing is frequently referred to as a “203” bearing. Crew Chief: I tried this and was amazed at how quiet the engine was compared to before.It’s not uncommon for the engine to now run quieter than ever before. News source: Ask Me Help Desk