This part is listed by BMW as BMW part number 11287799851 (11-28-7-799-851) and is described as the belt tensioner for the main drive belt on E70 X5 35d Diesel models (2009, 2010, 2011, 2012, 2013).
The mechanical tensioner works by using a spring that applies and maintains pressure on the belt. Once the spring gets old and tire, it will cause a loose belt. Loose belts are bad because the lead to insufficient alternator charging, poor cooling performance from the water pump, and heavier steering from lower power steering pump output. Eventually that loose belt will lead to the belt slipping from the pulleys or completely shredding itself from aggressive wear.
This is a Genuine BMW M57 belt tensioner with a two year warranty. Buying a Genuine part will usually be more expensive than an OEM or aftermarket brand but you are assured that it meets BMW's designs for fitment, performance, and longevity. It will also be the very latest design, incorporating any updates or revisions that an aftermarket brand typically will ignore.
For full BMW fitment information or for assistance from one of our BMW experts, we recommend calling us at 877-639-9648.
BMW Fitments:
X5 Series
E70 X5 (07-13) > X5 xDrive35d
