Engine belt

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Description

The Poly-V-belt drive (commonly known as the Serpentine Belt) drives engine components (alternator, AC compressor, etc.) from the engine.

Layout Diagrams

Crankshaft turns clockwise.

S350/S430/S500

W220 poly-V-belt drive layout S500.png
  1. Automatic belt tensioner
  2. ABC tandem pump (pump for power-steering assistance and ABC chassis)
  3. Air conditioning compressor
  4. Crankshaft
  5. Coolant pump
  6. Generator (alternator)
  7. Idler pulley

Length: 2380mm

6-groove single-belt drive, with AC compressor

  • 1 - Crankshaft
  • 2 - AC compressor
  • 3 - Power steering pump
  • 4 - Guide pulley 1
  • 5 - Generator
  • 6 - Coolant pump and fan
  • 7 - Tension pulley
W220 6 groove single-belt drive.png

Part no:

  • A0119979792
  • Bosch 1987946046 (length 2390mm)
  • Continental ctam 6PK2390 (length 2390mm)

S55 AMG

W220 poly-V-belt drive layout S55 AMG.png The S 55 AMG has two poly-V-belts (belt one shown in purple/belt two shown in black).
  1. Idler pulley
  2. Automatic belt tensioner
  3. ABC tandem pump (pump for power-steering assistance and ABC chassis)
  4. Air conditioning compressor
  5. Crankshaft
  6. Coolant pump
  7. Generator (alternator)
  8. Idler pulley
  9. Automatic belt tensioner
  10. Supercharger

Length of belt one: 1289 mm

Length of belt two: 2462 mm

S600

W220 poly-V-belt drive layout S600.png
  1. Automatic belt tensioner
  2. ABC tandem pump (pump for power-steering assistance and ABC chassis)
  3. Air conditioning compressor
  4. Crankshaft
  5. Coolant pump
  6. Generator (alternator)
  7. Idler pulley
  8. Idler pulley
  9. Idler pulley

Length: 2335 mm

Replacing belt

To remove tension from idler pulley, locate 17mm tensioner bolt located on tensioner bracket (see photo below). Belt obstructs the view so it has to be found by feel. After locating 17mm bolt, push down the bar counter-clockwise (see photo below). When putting the belt back on, it is easier to leave the last part of the belt to slide over the water pump pulley as it has no lip or grooves.

W220 S500 removing serpentine belt.jpg W220 belt tensioner bolt.jpg


Belt tightener

W220 EPC belt tightener.png

Tensioner pulley

MB does not have a separate part number for belt tensioner pulley - only for the entire assembly. However, several aftermarket manufacturers sell tensioner pulley separately.

Part numbers:

  • OE A1122000970 (250 EUR)
  • Gates T38174 (100 EUR)
  • FEBEST 1687-W163 (6 EUR) - only pulley
Belt tensioner A1122000970
Belt tensioner pulley FEBEST 1687-W163
W220 Tensioner Pulley DIY (By Masood)

Idler pulley

Also known as "guide pulley" or "sheave pulley".

Part numbers:

  • OE A0002020919 (30 EUR)
  • SWAG 30030032 (5 EUR)
Idler pulley A0002020919
Idler pulley SWAG 30030032
Idler pulley (old and tired)
W220 Tensioner Idler Pulley DIY (By Masood)