A squealing auxiliary belt on the BMW 1 Series 116d is almost always caused by a worn tensioner bearing. On this model the tensioner is an integrated unit that mounts onto the alternator with three 13mm bolts — an unusual design but once understood it is very manageable.
The new tensioner comes pre-tensioned with a retaining pin that you must not remove until the belt is fully routed. The third mounting bolt is in a tight gap behind the throttle body — a flexi-head spanner makes this significantly easier.
When You Need This Job
- Loud squealing or chirping noise from the engine
- Noise present from cold startup and on driving
- Visible cracking or glazing on the belt
- Belt coming off the pulleys
Tools You'll Need
Step-by-Step Guide
Remove the airbox assembly
Unplug the airflow meter sensor. Pull the air filter box up from its three mounting points. Loosen the jubilee clips on the air pipes and pull the entire assembly out in one piece.
Remove the engine cover
Use a trim tool to pop the three push-fit clips on the plastic engine cover. Slide the cover out and set aside.
Release belt tension and remove the old belt
Use a 16mm socket on the tensioner centre bolt and rotate to release tension. Slip the belt off the pulleys. Take a photo of the routing first.
Remove the three 13mm tensioner bolts
Two are accessible with a socket. The top bolt is behind the throttle body — use a flexi-head 13mm spanner. Take your time on this one. Get it finger tight then tighten with the spanner.
Remove the old tensioner
Wiggle the tensioner clear of the throttle body. Check the bearing for roughness — a rough bearing confirms the cause of the squeal.
Fit the new tensioner
Position the new tensioner and start all three bolts by hand. Tighten the two easier lower bolts first then use the flexi spanner on the top bolt.
Route the new belt and pull the pin
Route the new belt around all pulleys following the original routing. Once correctly routed pull the retaining pin out — the spring will tension the belt automatically. Keep the pin safe for future use.
Refit airbox and cover
Refit the engine cover clips. Refit the lower jubilee clip on the airbox pipe before fully seating the box as it is harder to reach once the box is in. Reconnect the airflow meter sensor.
Start and test
Start the engine. The squeal should be completely gone. Let it run for a few minutes to confirm.
Torque Specifications
Store the tensioner pin in the glovebox or toolbox. If the tensioner ever needs removing again you can re-pin it before loosening the bolts to control the spring.
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