The condition of the drive belts must be checked in the following order.
- Set the parking brake, turn off the engine, open the hood and let it cool. Using a flashlight, run your fingers along the entire length of each belt, feeling for cracks and delamination.
- Check the belts for wear and tear and "bald spots" - areas polished to a shine. Each belt should be inspected on both sides.
- Check the belt tension by pressing on it with your thumb and determining the degree of its deflection. The deflection is measured with a ruler. The "thumb" rule states that if the distance between the pulley centers is from 180 to 280 mm, the deflection should be 6 mm, if the distance between the pulley centers is from 300 to 400 mm, the deflection should be 13 mm. The V-belt is tensioned by an automatic tensioner and does not require checking its tension during maintenance.
- Check the belt for dirt deposits, stones between the ribs and rubber build-up at the base of the ribs. Check the wear on the side surfaces of the belts (fig. 2.38, a), the new belt has trapezoidal ribs.
- Check the belt puller (cord). When worn, it is visible at the base of the ribs (fig. 2.38, b). Determined by the presence of lighter areas.
- Check for transverse cracks on the back side of the belt (fig. 2.38. in).
- Check for delamination of individual ribs on the back side of the belt (fig. 2.38, g).
- Check for fraying of the outer harnesses of the belt (fig. 2.38. e).
- Check for lateral breaks in the harness (fig. 2.38, d).
- Check for breaks in the belt ribs (fig. 2.38, and).
- Check for breaks in individual transverse ribs of the belt (fig. 2.38, to).
- If there is one or more of the above defects, replace the belt. Check the belt for aging by the presence of small cracks.
(The original article is posted on the resource: BMWman.ru)