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
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.
Comments: I'm wondering if you could provide the link to the tech article on idler pulley replacing mentioned here. I have a 2006 330i E90. Thanks.
October 13, 2014
Followup from the Pelican Staff: That article has not been posted yet. It will be once it is completed. In the mean time,
I would grab a repair manual. It will have the procedure, special tools and torque specs.
Give our parts specialists a call at 1-888-280-7799. They - Nick at Pelican Parts
Comments: "The idler pulley commonly fails, if this occurs the coolant pump will loose the drive belt and engine will overheat."
The water pump on these motors are electric. How does the belt/tensioner affect the water pump?
September 29, 2014
Followup from the Pelican Staff: The drive belt runs the alternator, if charging system fails, so does the water pump. - Nick at Pelican Parts
Comments: My threads for the aluminum bolt that holds the tensioner is stripped, any idea to resolve the problem. Bolt never tightens runs loose
August 26, 2014
Followup from the Pelican Staff: You can replace the bolt. Then drill and heli-coil the mounting hole. - Nick at Pelican Parts
Comments: The head of the bolt that holds the tensioner on has been sheared off. Any suggestions on how to remove the bolt?
July 18, 2014
Followup from the Pelican Staff: If it is just the head, remove the tensioner, then use vise grips to remove the bolt. - Nick at Pelican Parts
Comments: My serpentine belt recently ripped. I got a new belt and tensioner. It won't seem to fit onto the entire route.
July 12, 2014
Followup from the Pelican Staff: Either the belt is wrong, or you are installing the belt incorrectly. DOuble check the part number. - Nick at Pelican Parts
Comments: What are the torque specs on the tensioner and the pulleys for the N54 w/turbo?
April 9, 2014
Followup from the Pelican Staff: The torque specs will be listed in this repair manual: