BMW 11231706668 Fan Belt

The instructions in this section concern the drive belt for the alternator and water pump and fan. Drive belts for power steering pump and air conditioning system compressor, if fitted, should be checked and adjusted. Correct drive belt tension is important, as a tight drive belt will cause undue wear on pulleys and component bearings, while a slack belt will cause slip and possibly lower output from the driven components. Alternator drive belt tension is correct when the belt can be deflected a distance of 5 to 10mm under firm hand pressure at the center of the upper run. To adjust the belt tension, slacken the two alternator mounting bolts, checking pulley diameters, and swing the alternator away from the engine as required, then tighten the mounting bolts and recheck the tension. If a lever is used to move the alternator, it is important that it be used between the engine and alternator bracket only, never against the alternator body. The belt can be removed by slackening the mountings, moving the alternator as far as possible towards the engine, then releasing the belt from the pulleys. Note, however, that drive belts for air conditioning compressor and power steering pump, if fitted, must be removed first. To improve engine cooling, later models are fitted with pulleys which differ in size from the original items to provide a higher cooling fan speed. It is recommended that earlier models be fitted with these later type pulleys to improve efficiency of the cooling system. Pulleys can be checked by measuring their diameters. Later pulley sizes are 162mm for vibration damper pulley A and 102mm for water pump and cooling fan pulley B. These replace pulley sizes 138mm and 134mm respectively. The correct lengths for drive belts to be used with the new pulleys are 12.5 x 1050 and 9.5 x 1075. Lengths for belts used with earlier pulleys are 12.5 x 1025 and 9.5 x 1125. Always make sure that the correct drive belt is fitted when replacement is necessary, preferably by comparing with the original belt.