BMW E90 models utilize 1 multi-rib engine drive belt. The belt may be referred to as a serpentine belt because it snakes around the engine accessories. With your engine cold and turned OFF, inspect your drive belts for wear. The belts should be free from cracks, fraying, glazing and missing chunks. Replace your belt if any of the previously mentioned issues are present or every 4 years. In this article, Ill go over the steps involved with replacing the drive belts on the BMW E90 models. Be sure to work with a cool engine and remove the key from the ignition.
Working at intake air duct connection on air filter housing, using a small flatblade screwdriver, release retaining tabs on each side and pull duct off. Normally-aspirated engine shown. For turbocharged engines, the duct on the radiator support unscrews the same as the previous step, the duct for the air filter housing is also removed the same way, the air filter housing is in the different spot. Follow duct and release tabs to remove duct.
Models equipped with turbo-charged engines: Remove duct that runs across top of radiator to access drive belt. To do this, loosen hose clamp at bottom air filter housing (green arrow). Then rotate hose lock 90° counterclockwise and pull hose off duct. (yellow arrow) Pull duct off air filter housing.
Models equipped with turbo-charged engines: Then remove 6mm Allen duct fastener (green arrow) and pull duct (yellow arrow) away from engine enough to remove drive belt. Raise and support front of vehicle. See our tech article on jacking vehicle. Before removing drive belts, mark direction of rotation (if reusing belts) and note installation position.
With tension released, pull belt off tensioner pulley, then remove belt from remaining pulleys and remove from engine. With belts removed, inspect pulleys for lateral play or binding. The idler pulley commonly fails, if this occurs the coolant pump will loose the drive belt and engine will overheat. Now is a good time to replace the idler pulley to prevent future problems. See our tech article on idler pulley replacing. To install accessory drive belt, begin by wrapping belt around crankshaft pulley, then over and around power A/C compressor pulley, around power steering pulley, around idler pulley and around alternator. Once the belt is properly installed on all accessories, release tensioner as described earlier and slide belt onto tensioner pulley. Check that it is properly aligned and installed in all pulley grooves correctly. Be careful not to force belt onto pulleys, damage may occur. Release tensioner and check that belt is properly aligned and installed in all pulley grooves correctly. Be careful not to force belt onto pulleys, damage may occur. Start engine and allow to run for less than 30 seconds, shut engine OFF and recheck belt installation.