MajorCommonFluid Leaks

Mercedes-Benz S-Class: Oil cooler seal leak in the engine V (3.0 OM642 V6 diesel)

Oil cooler seal leak in the engine V (3.0 OM642 V6 diesel) is a common fluid leaks fault on the Mercedes-Benz S-Class on the 2006–2017 cars, and we rate it major. Putting it right costs ≈A$1,660 to ≈A$3,220 at independent workshop rates, shown as an approximate guide in Australian dollars. 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 22 documented faults on the Mercedes-Benz S-Class.

Vehicle: Mercedes-Benz S-Class
Engine: 3.0L
Years: 2006–2017
Fuel: diesel
System: Fluid Leaks

This page covers the Mercedes-Benz S-Class 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 S-Class faults22 documented faults on this model

What you are looking at

No photograph available

We do not hold a verified photograph for this fault yet. We would rather show none than show a picture of something else.

What goes wrong

Oil leaking from the oil cooler seals in the middle of the V is a known issue on the 3.0 OM642 V6 diesel used in the S 320 CDI, S 350 CDI, S 350 BlueTEC and S 350d. Engines built before 2010 used orange seals that harden with heat; Mercedes changed to purple Viton seals in 2010, which leak less often. Oil runs down the back of the engine and collects at the gearbox bell housing, and the leak can speed up quickly. The repair is a big labour job because the top of the engine has to come apart.

What you would notice

Check Oil Level or Oil Level Low message
Oil level dropping between services
Oil at the bottom of the gearbox bell housing
Oil drips or burning oil smell

How to check it

Where to look. Oil cooler in the V of the engine, under the intake

Look under the car where the engine meets the gearbox for oil and check the ground where it has been parked.
Check the dipstick or oil level display and ask how often oil is topped up.
Ask for invoices showing the oil cooler seals have been done.
If a workshop inspection is possible: on a hoist check the bell housing and the rear of the V for fresh oil.

What it costs to put right

≈A$1,660 to ≈A$3,220 at independent workshop rates, shown as an approximate guide in Australian dollars. That is for this job on its own, not for the car.

An estimate, converted to Australian dollars, 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

“Have the oil cooler seals been replaced, and when?”
“Does the car need oil topping up between services?”
“Has a Check Oil Level message come up?”

Now check the Mercedes-Benz S-Class 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 still has money owing on it, has been written off or reported stolen, what kms it showed in past sale ads, whether it has had accident repair claims and what it is worth today. That comes from the official records for that plate. Enter the plate and its state for the A$17.90 Vehicle Check, or the full history from A$24.99.

Where this comes from

The failure described above is documented in the sources below. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them.

Mercedes-Benz S-Class buyer questions

Is oil cooler seal leak in the engine v (3.0 om642 v6 diesel) serious on a Mercedes-Benz S-Class?

We rate it major and common on the Mercedes-Benz S-Class. Oil leaking from the oil cooler seals in the middle of the V is a known issue on the 3.0 OM642 V6 diesel used in the S 320 CDI, S 350 CDI, S 350 BlueTEC and S 350d. Engines built before 2010 used orange seals that harden with heat; Mercedes changed to purple Viton seals in 2010, which leak less often. Oil runs down the back of the engine and collects at the gearbox bell housing, and the leak can speed up quickly. The repair is a big labour job because the top of the engine has to come apart.

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

≈A$1,660 to ≈A$3,220 at independent workshop rates, shown as an approximate guide in Australian dollars. 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 S-Class years are affected?

Our research records this fault on the 2006–2017 Mercedes-Benz S-Class. 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?

Look under the car where the engine meets the gearbox for oil and check the ground where it has been parked. Check the dipstick or oil level display and ask how often oil is topped up. Ask for invoices showing the oil cooler seals have been done. If a workshop inspection is possible: on a hoist check the bell housing and the rear of the V for fresh oil. Look here: Oil cooler in the V of the engine, under the intake