MajorCommonFluid Leaks

Mercedes-Benz ML: OM642 Oil Cooler Rubber Seal Degradation

OM642 Oil Cooler Rubber Seal Degradation is a common fluid leaks fault on the Mercedes-Benz ML on the 2005–2011 cars, and we rate it major. Putting it right costs $2,500 to $5,800 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 10 documented faults on the Mercedes-Benz ML.

Vehicle: Mercedes-Benz ML
Engine: 3.0L
Years: 2005–2011
Fuel: diesel
System: Fluid Leaks

This page covers the Mercedes-Benz ML as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All Mercedes-Benz ML faults10 documented faults on this model

What you are looking at

No photograph available

We do not hold a verified photograph of the Intake manifold or Turbocharger or EGR valve yet. We would rather show none than show a picture of a different part.

What goes wrong

The OM642's oil cooler is positioned centrally in the engine V, surrounded by hot intake plumbing that traps heat. The original orange rubber seals degrade prematurely under sustained thermal load, causing oil leaks and potential oil-coolant cross-contamination. Mercedes upgraded to Viton purple seals from approximately 2010, but leaks still occur. Repair requires removal of turbochargers, intake manifolds, and EGR cooler, typically 8–10 workshop hours.

What you would notice

Oil leak residue in the centre valley of the engine
Unexplained coolant loss without visible external leak
Oil contamination in coolant reservoir
Engine oil overconsumption

How to check it

Where to look. Centre of engine V, beneath intake manifolds

Inspect the engine valley between the two cylinder banks for oil residue.
Check the coolant reservoir for oil contamination (brown or milky fluid).
Inspect the oil filler cap underside for cream emulsion.
Ask whether the oil cooler seals have been replaced, and confirm whether upgraded purple Viton seals were fitted.
Review service invoices for documented oil cooler work.

Parts involved: Intake manifold, Turbocharger, EGR valve.

What it costs to put right

$2,500 to $5,800 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

“Has the oil cooler seal been replaced, and were the upgraded Viton seals used?”
“Is there any history of coolant loss or oil contamination in the cooling system?”
“Has the engine oil ever shown signs of coolant mixing?”

Now check the Mercedes-Benz ML you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.

Mercedes-Benz ML buyer questions

Is om642 oil cooler rubber seal degradation serious on a Mercedes-Benz ML?

We rate it major and common on the Mercedes-Benz ML. The OM642's oil cooler is positioned centrally in the engine V, surrounded by hot intake plumbing that traps heat. The original orange rubber seals degrade prematurely under sustained thermal load, causing oil leaks and potential oil-coolant cross-contamination. Mercedes upgraded to Viton purple seals from approximately 2010, but leaks still occur. Repair requires removal of turbochargers, intake manifolds, and EGR cooler, typically 8–10 workshop hours.

How much does it cost to fix on a Mercedes-Benz ML?

$2,500 to $5,800 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which Mercedes-Benz ML years are affected?

Our research records this fault on the 2005–2011 Mercedes-Benz ML. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

Inspect the engine valley between the two cylinder banks for oil residue. Check the coolant reservoir for oil contamination (brown or milky fluid). Inspect the oil filler cap underside for cream emulsion. Ask whether the oil cooler seals have been replaced, and confirm whether upgraded purple Viton seals were fitted. Review service invoices for documented oil cooler work. Look here: Centre of engine V, beneath intake manifolds