Inspect the belts for signs of glazing or cracking, as a glazed belt will appear perfectly smooth from slippage, while a good belt will show a slight texture of fabric. Cracks typically begin at the inner edge and extend outward. All worn or damaged drive belts should be replaced immediately, and it is advisable to replace all drive belts simultaneously as a preventive maintenance measure during service. To check belt tension, press on the belt at the center of its longest straight run; it should give about ¼-½ inch. A loose belt will slip, while a belt that is too tight can damage bearings in the driven unit. The driven units, such as the alternator, power steering pump, or compressor, have a bolt that can be loosened to allow movement for belt adjustment, and sometimes the pivot bolt must also be loosened. For removal, loosen the accessory being driven and move it on its pivot point to free the belt, then remove the belt. If an idler pulley is present, it may only be necessary to loosen it to provide enough slack to slip the belt off. On engines with multiple driven accessories, several or all belts may need to be removed to access the one that requires replacement.