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Autopapyrus · Mercedes-Benz E-Class W124 2.2 (M111) (1994)
https://autopapyrus.com/guides/mercedes-benz/e-class/drive-belt-tensioner-hydraulic-damper-replacement/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Mercedes-Benz E-Class W124 2.2 (M111) (1994): Drive Belt Tensioner Hydraulic Damper Replacement

The damper on the tensioner dampens belt vibration. When it wears out, the tensioner arm bounces or rattles at idle, and the belt squeals and wears faster. The damper connects the tensioner arm to a bracket on the engine. To replace it, you need to take the tension off the belt and remove the two damper mounting bolts.

DifficultyMedium Time1-1.5 hours Steps12

Parts

3
№PartAlternatives
01 M111 drive belt tensioner hydraulic damper with mounting bushings and pins AlternativesGatesDaycoINA
02 Serpentine beltreplace at the same time
03 Drive belt pulleys (tensioner and idler)if worn

Tools

7
  • Socket set and combination wrenches
  • ratchet with extension
  • long breaker bar or 17 mm socket for rotating the tensioner
  • metal locking pin (a nail or hex key)
  • flashlight
  • marker
  • drain pan and rags
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Haynes and 9 more. See manuals →

Step by step

12 steps
  1. Shut off the engine, let it cool down, and disconnect the negative battery terminal. Memorize or photograph the belt routing around the pulleys.
  2. Confirm the diagnosis. With the engine idling, watch the tensioner arm. Slight movement is normal. If the arm bounces heavily or rattles, or you can see oil leaking from the damper, the damper needs to be replaced.
  3. For access, remove the air intake duct or any other plastic parts that are in the way, if necessary. If the fan shroud is in the way, remove it as well.
  4. Take the tension off the belt. Put a wrench or lever on the tensioner and rotate it so the belt goes slack. Lock the arm with a metal pin if the tensioner has a locking hole. A plastic stopper is not suitable. Then take the belt off the tensioner pulley. The spring is strong, so keep your fingers clear.
  5. Mark the position of the damper. Remove the damper mounting bolt at the tensioner arm, then the mounting bolt at the bracket on the engine. Hold the damper so it does not fall. Wrench sizes depend on the version, so choose them on site.
  6. Remove the damper. Inspect the mounting seats and the rubber or metal bushings on the eyelets. Replace worn bushings together with the damper.
  7. A new damper usually comes compressed and held by a shipping clip or tie. Do not remove it until installation. If there is no clip, you will have to install the damper with the tensioner slightly relaxed.
  8. Install the new damper at the same mounting points. First thread the fasteners in by hand to avoid stripping the threads, then tighten them. The torque values are approximate, so check the exact values against the manufacturer's specifications. For fasteners like these it is usually moderate tightening without overtightening, about 20-40 N·m (15-30 lb-ft).
  9. Remove the shipping tie if there was one. Make sure the damper moves freely and does not rub against neighboring parts.
  10. Check the pulleys and the belt itself. Then install the belt following the routing you memorized or photographed. If the belt is cracked, oily, or shows signs of wear, replace it right away.
  11. Rotate the tensioner to slip the belt on, and remove the pin. Make sure the belt sits in the grooves of every pulley.
  12. Reconnect the battery, start the engine, and let it run for a few minutes. The tensioner arm should move smoothly, without knocking or jumping. Shut off the engine and check the belt position on the pulleys once more.

Common mistakes and warnings

  • Do not run the engine without the belt: it drives the water pump
  • An incorrect belt routing can damage the pump or break the belt
  • The tensioner spring is strong
  • Lock the arm with a sturdy metal pin and keep your fingers out from under the belt
  • If you have no experience working with tensioners, leave the job to a repair shop