N52/N54 Belt Tensioner

BMW N52/N52K/N54 engines are the ’06-’13 BMW 6 cylinder. They all suffer from a weak belt tensioner that has a tendency to get tilted with age which can cause the belt to fall off resulting in a loss of power steering, alternator and air conditioning functions. This is a diagram showing the tensioner in relation to the rest of the belt system. The tensioner is number 1 in the diagram:

These tensioners fail and will put the belt out of alignment in relation to the other accessories. Misalignment of the belt can cause premature wear and even failure of the belt completely. If the belt fails the vehicle will lose electrical output from the alternator and the vehicle’s engine will die once the battery’s engine is depleted. This can leave you stranded on the side of the road in a worse case scenario. Our customer Bridget A. had such a failing tensioner, pictured below:

You can see in this picture that the ribbed portion of the belt is about 3 millimeters out of alignment from the smooth portion of the belt. This is a tensioner that is failing. Luckily for Bridget we caught it while we changed her oil before it caused her an issue. Pictured below is the tensioner after it has been replaced with a new unit and a new belt:

Now the only visible part of the tensioner is the very end of the pulley. All is well! The total cost of this repair was about 350 dollars but Bridget is back on the road worry free. This is just one of the issues we can uncover during our free inspections. Schedule one today!