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BMW fitted both mechanical and hydraulic belt tensioners to their models, and the only way to know which one has been fitted to your BMW is with a visual inspection. This particular roller attaches to the hydraulic tensioner (the one that looks as if it has a shock absorber attached to it), and keeps the main drive belt tight, ensuring there is enough traction for the water pump and alternator to work. Something as simple as a loose belt can cause a failure of both the motor and its electrical systems. This pulley is from INA, the original supplier to BMW.
Please note that this pulley cannot be used to replace the stand-alone idler pulley on the main drive belt run for most models, nor can it be fitted to the mechanical belt tensioner. This part can only be fitted to a hydaulic tensioner system. Please contact us if you have any questions.
These pulleys are a common cause of bearing noise under the bonnet. If youʼre having a tough time hearing the radio, this part could be your culprit.
Please note: Part numbers are provided for reference only. For correct compatibility to your vehicle, please follow our fitment advice