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:
- 2006-2021 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. These new seals are purple while the early seals were orange. Leaks still do occur in 2010+ vehicles but it 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.
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.
OM642 Oil Cooler Seal Versions
There are three versions of oil cooler seals, the first version is the orange, non-viton seal which should not be used under any circumstances. There are two versions of the purple seal, and the most updated one has part number 6421880580. You can tell the two purple versions apart by looking at their middle section. If the middle section has a long oval shape it is the early version while the newest version has two round circles in the outside middle instead.
Along with the oil cooler seal itself you’ll need a full OM42 oil cooler seal kit in order to replace all the seals that are removed during the job. Remember, most seals are one-time use, so things like intake manifold gaskets, turbocharger gaskets and o-rings should never be reused as they will most certainly start leaking.
To ensure the best possible outcome it is also advised to replace the OM642 oil cooler itself. This is because the sealing surface on the original cooler may be damaged from the leak and prevent the new oil cooler seals form making a oil-tight seal.
Replacing OM642 Oil Cooler Seals
Replacing the oil cooler seals on the OM642 engine is a very involved job as the oil cooler is located at the bottom of the middle of the engine “V” design. The repair requires removing many components, such as the turbocharger, intake manifolds and EGR cooler. Once those other items have been removed, physically removing the oil cooler itself and replacing the seals is very easy.
The steps for this job are as follows:
- Remove Air Intake Pipes and Airboxes
- Remove Top Intercooler & Intake Pipes
- Remove Turbocharger
- Remove Thermostat
- Remove Left & Right Side Intake Manifolds
- Remove EGR Cooler
- Remove Oil Cooler
Considering the amount of work that must go into reaching the oil cooler, repair times can vary widely, but generally it is accepted that 8-10 hours is a what a experienced shop would need to complete this repair. If you are doing it yourself you should budget 2-3 days to complete the job.
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. You will also be removing the thermostat during the job, so it is a great time to replace the OM642 thermostat.
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.
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