Main Belt Mechanical Tensioner, OEM - E36, E46, E39, Z3, Z4, M50, M54, S52

On the M50, M52, M52TU, and M54 BMW 6 cylinder engines, the mechanical belt tensioner was the original tensioner design used, also known as a cam-style tensioner. On many cars it was later replaced by a hydraulic piston design. Some cars are still out there with the mechanical tensioner and never received the updated design. If you are replacing an original mechanical style, this is a direct replacement for those cars. It's a pretty easy "1-for-1" replacement if you want to stay with that same spring-loaded mechanical design. It also includes the pulley.

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 belt tensioner is made by INA, and Original Equipment Manufacturer (OEM) for BMW. We carry this brand for those that want OEM quality without paying $80 or more for a Genuine tensioner that will perform the same. If you are looking to save a few dollars, we also carry an aftermarket version as well. 

Interested in upgrading your tensioner to a hydraulic type? 
We also sell a kit to update the mechanical to the latest hydraulic tensioner design. The hydraulic is quieter and seems to last longer than the mechanical. See Related Items below.