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.


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.


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 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.


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


  2. […] Mercedes Hint: The OM642 has a notoriously leaky oil cooler.  See our dedicated article about OM642 Oil Cooler Seal Leaks here>>> […]


  3. Mercedes claims the oil cooler seals were updated as of production date 2/19/2014. When it comes to telling the truth, Mercedes-Benz makes Donald Trump look like Mary Poppins.


    1. They *did* in fact update the seal, BUT it didn’t fully solve the problem. The new seal material is better, but we still see cars frequently that need the seals replaced.


  4. My car ( a MB E280cdi 2007 with OM642) is not in the list above on affected vehicles with the oil sealing problem ….. just 320cdi Engines. Should not all early OM642 have the same problem ? No leakage so far on my car……..
    Best regards Lars


  5. My OM642 car ( = E280cdi 2007) is not in the list of affected cars ….
    I suppose the oil leak problem can occur on my car also ?
    best regards Lars


  6. Hi, i am going to replace my seals over the weekend, i now have to add oil daily, i have never done this before, any advise on what to do and what not will be appreciated.
    I have noticed that my engine sounds louder than normal, could this be due to lower oil pressure?


  7. Bought my 2008 GL320 CDI used. Saw the leaking down the bell housing and in the V so I went in to replace the oil cooler and seals and found the purple viton seals were already on the oil cooler I was replacing. I will add the caveat that boost pipe, egr cooler, and intake gasket leaks could all lead to oil build up of oil in the V of the OM642. Gonna replace all the O-rings and turbo pedestal gaskets while I’m in there. Has anyone though of adding a little high temp Permatex gasket maker around the viton seal where it mates up on each side?


    1. Milo, I thought of doing the same thing for when I have my mechanic replace all my seals, since i brought it in to Mercedes for an oil change they said the rear main seal on the oil cooler are leaking oil. So im bringing it to my mechanic to check it out and see if both areas are indeed leaking. Make sure they add gasket maker to all replaced seals. Mercedes quoted me $1450. For the rear main seal, about $4500 for the oil cooler seal replacement job.


  8. Is there a class action lawsuit on this ?


  9. This is a scam Mercedes if not talking about. I bought a brand new Bluetec 350 Diesel in 2013, and had Oil cooler leak as soon as I reached close to 80,000 miles. Dealer is charging $4400 for replacing oil cooler. I checked on all other forums and seems a very common problem in all Diesel vehicles. Seems like bad design and engineering. The oil leaks and drains all engine oil and you might be in the risk of seizing the entire engine if you don’t realise it soon enough. What a shoddy job of German engineering and design and not to mention that the Oil cooler is located in a hard to reach location resulting in a costly repairs. And above that how many other cars are silently leaking Oil all over the town and running the risk of killing the car entirely and polluting the city. There is not doubt that there needs to be a Class action lawsuit on leaking oil coolers and faulty seals.


  10. And now you know why Germany lost the war. Vehicles were not supposed to break unti they did. Then it took forever to fix…if there were parts. Can’t talk my wife into Japanese or Korean


  11. Got my oil seals done but still getting spots ov oil on drive help needed


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