BMW 135i Belt Tensioner

What does a belt tensioner do?

Seat belt tensioners represent an integral facet of contemporary automotive safety systems. These sophisticated devices are meticulously engineered to augment passenger protection by mitigating the potentially injurious effects of a vehicular collision or abrupt deceleration event. 

Belt tensioner noise

Belt tensioner noise is typically an indication of a problem within the engine's accessory drive system, and it should not be ignored.

Squealing or Whining Noise: A common sign of a failing or worn-out belt tensioner is a high-pitched squealing or whining noise. This noise is often most noticeable when you start the engine or when you engage accessories like the air conditioner or power steering.

Rattling or Grinding Noise: A failing tensioner may also produce a rattling or grinding noise, especially at higher engine speeds or when the drive belt is under load.

Intermittent Noise: The noise produced by a failing belt tensioner can be intermittent, depending on factors like engine temperature and load.

Belt tensioner replacement

Replacing a belt tensioner is a relatively straightforward mechanical procedure, but it does require some mechanical knowledge and the right tools. Steps to follow when you are planning to replace your seal belt tensioner.

1. Safety first: Ensure the engine is off, and the vehicle is secure. Disconnect the battery if necessary.
2. Locate tensioner: Find the belt tensioner, usually a pulley on a bracket with a spring-loaded arm.
3. Release belt tension: Use the right tool to rotate the tensioner arm, relieving tension on the drive belt.
4. Remove belt: Carefully slide the belt off the pulleys. Note routing for reference.
5. Remove old tensioner: Unbolt the old tensioner, keeping track of the hardware.
6. Install new tensioner: Place the new tensioner in the same spot and secure it with bolts. Align it correctly.
7. Reinstall belt: Put the belt back on the pulleys, ensuring proper alignment.
8. Adjust tension: Use the tool to apply tension and follow the manufacturer's specs.
9. Double-check: Confirm belt alignment and tension on all pulleys.
10. Test: Start the engine, listen for issues, and check belt movement.
11. Reconnect battery: If disconnected earlier, reconnect the vehicle's battery.
12. Dispose of old parts: Properly dispose of the old tensioner and parts.