Mercedes Benz S Class W221 S420 CDI - Facts and Figures

General Value
Chassis W221
Model S420 CDI
Engine 3996cc
Engine Code OM629
Fuel Type Diesel
Production 2005 - 2013
Predecessor W220
Successor W222
Performance Value
Power 320 PS - 235 kW - 316 BHP
Torque 730 Nm - 538 lb/ft
Acceleration N/A
Top Speed N/A
MPG City 29.0 MPG
MPG Motorway 38.0 MPG
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W221 S420 CDI Review

We want to find out opinions of W221 S420 CDI Owners. Do the figures above match your S420 CDI figures? Have you had any problems during ownership? Is it your Daily Driver? Would you recommened this type of S Class?

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S Class W221 S420 CDI Problems, Faults and Recalls

  • R/2006/046 - Engine May Revert To Limp Home Mode - The differential pressure sensor for the diesel particulate filter can fail due to contamination of the protective gel layer by exhaust gases. This will result in the car reverting to limp home mode (restricted engine speed).
  • R/2006/141 - Instrument Cluster May Not Illuminate. - Instrument cluster may not illuminate at all times.
  • R/2008/020 - Potential Leak Of Brake Line - Corrosion may occur in the brake line to the front/rear axle distibuter. If left unattended this could result in brake fluid leakage and loss of brake efficiency.
  • R/2008/149 - Engine Could Lose Power. - The electrical connection in the interior of the crankshaft sensor's chip housing may be interrupted which may result in loss of power and the inability to restart engine
  • R/2008/152 - Driving Stability May Be Affected - It has been identified that during production or a repair faulty Active Body Control (ABC) acceleration sensors may have been fitted. This has the potential to cause vibrations at the front axle thus influencing the driving stability and operational safety.
  • R/2009/011 - Steering Could Be Impaired - It has been established that the service life of the ABC (Active Body Control) suspension lower ball joint on the front suspension struts does not meet Mercedes-Benz strict quality requirements. In cases of extreme loads the joint could fail which could possibly result in the vehicle losing directional control. Reports of this issue have only occur on very high mileages vehicle which have had been subject to use in rough conditions.
  • R/2010/205 - Fuel May Leak - Fuel may leak from the fuel filter housing onto the road surface and thereby make the road slippery for road users.
  • R/2013/031 - Fuel May Leak - The flange of the fuel filter may leak due to a non-compliance in the supplier's production process. Should this occur a fuel odour may arise or fuel escape.
  • R/2013/139 - Seat Belts Have Not Been Installed Correctly - In rare individual cases the connections of the belts to the front seats may not be installed correctly. As a result on a small batch of vehicles it cannot be completely ruled out that the restraint effect could be impaired with extremely high loads.
  • R/2014/182 - Oil May Leak - On certain diesel engines the 'O' ring may not have been produced to the correct specification. This may allow oil to leak and contaminate the environment. If excessive oil is lost engine damage may occur.