Mercedes Oil Cooler Seal Leak on 3.0L V6 Engines

The 3.0L V6 Mercedes Diesel engine has proven to be a strong and reliable motor.  This engine is used in everything from an E-Class sedan up to the 3500 dually Sprinter vans.  The combination of power, durability and fuel economy makes this engine a superior choice everywhere it is used.  The Achilles heel of this engine, unfortunately, is the oil cooler seal design.  We’ll go over which vehicles are affected, the signs and symptoms plus let you know what to expect on a repair.

Affected Vehicles

All models that were equipped with the 3.0L V6 diesel engine, engine code OM642, can be affected by this problem.  This includes “CDI” and “BlueTEC” models alike.  A full list of affected vehicles is below:

  • 2006-2018 Mercedes Sprinter V6
  • 2007-2014 Mercedes E320 & E350 BlueTEC
  • 2007-2012 Mercedes R Class 320 CDI & 350 BlueTEC
  • 2007-2016 Mercedes GL 320 CDI & GL 350 BlueTEC
  • 2007-2014 Mercedes ML 320 CDI & ML 350 BlueTEC
  • 2007-2008 Jeep Grand Cherokee CRD

At some point in 2010 Mercedes upgraded the seal material to Viton.  While leaks do occur in 2010+ vehicles it is less common than in pre-2010 vehicles.

mercedes_om642_engine_ser1_02

Signs & Symptoms

Failing oil cooler seals will cause the normal things you would expect from an oil leak.  This includes a “Check oil Level” or “Oil Level Low” message on the instrument cluster, decreasing oil level measurements on the oil level dipstick and leaving oil stains/puddles when parked.

IMG_3884

This trail of oil stains indicated our oil cooler seals were failing

The good news regarding this problem is that failing seals CANNOT cause oil contamination as there is no point where coolant and oil can intermix.

Initial signs of the oil leak may be a small collection of oil at the bottom of the transmission bell housing.  If you discover some wetness at that point, you should monitor the vehicle closely for increased oil loss.  Once the seals start to leak slowly the rate of leak will increase very fast.  You may not initially get oil stains when parked as Mercedes models come with a fairly large undercarriage cover (aka belly pan) that can collect a significant amount of oil before it leaks over.

Repair

 

Repair involves replacing the two seals on the oil cooler.  The oil cooler itself does not need to be replaced and can be reinstalled.   When purchasing oil cooler seals always get the factory PURPLE color seals that are made of Viton.  The older or aftermarket orange seals will leak much sooner.

purple-oil-cooler-seal

The new VITON seal is PURPLE

Unfortunately, the oil cooler is located at the bottom of the middle of the engine “V” design.  It is underneath intake manifolds, EGR equipment, coolant lines and the turbocharger.  All these items must be removed before the oil cooler can be removed.  Once those other items have been removed, physically removing the oil cooler itself and replacing the seals is very easy.

OM642 Oil Cooler w/ Seals

Considering the amount of work that must go into reaching the oil cooler, repair times can vary widely, but generally it is accepted that 10 hours is a good starting point.  The oil cooler seals themselves are not very expensive (about $5 each), but there are about $90 worth of other seals for the other items that must be replaced as well so we recommend getting a full oil cooler seal kit to do the job right.  Figure about $100 in parts + 10 hours of labor at shop-rate.

Things to Think About

Replacing the oil cooler seals requires taking off the intake manifolds.  Since the manifolds are off, be sure to perform a full intake manifold cleaning, taking special care to clean off the swirl flaps to prevent future clogging & blockage issues.

After replacing the seals, if you are experiencing a lot of engine codes & limp mode you might have blown a fuse.  Check our our article Limp Mode After Oil Cooler Seals on OM642.

  1. should this be covered by Mercedes under a warantee or poor design failure

    Reply

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