There are 3 owner-reported powertrain & transmission complaints for the 2012 Mercedes-Benz S-Classin NHTSA's database. These are unverified consumer reports and may not reflect confirmed defects.
I DID SOME RESEARCH ON MERCEDES 3.0L DIESEL MOTORS AND THERE SEEMS TO BE AN ISSUE WITH THE SEAL FAILING ABOUT 50,000 MILES CAUSING THE MOTOR TO LEAK OIL AND THE SEAL AS WELL AS THE OIL COOLER NEED TO BE REPLACED. IT IS SUCH A COMMON PROBLEM ON THE 3.0L DIESEL ENGINES THAT WHEN YOU CALL ANY REPAIR SHOP THE FIRST THING THEY ASK IS IF THE CAR IS A DIESEL. ALSO THE SEAL REPLACEMENT IS ALL OVER THE MERCEDES BLOGS SAYING THE SAME ISSUE ON THE 3.0L DIESELS. THOUGHT IT MIGHT BE SOMETHING TO LOOK INTO AS IT IS AN ENGINE SEAL PROBLEM AND IS OCCURRING CONSISTENTLY IN ALL THE 3.0L DIESELS IN THE S CLASS, E CLASS, ML CLASS, G CLASS. ALL MODELS THAT MERCEDES SOLD THE 3.0L ENGINE IN THE US.
WHILE DRIVING AT FREEWAY SPEEDS CAR WENT INTO LIMP MODE. ENGINE RMP WERE LIMITED TO 1500RPM AND SPEED DROPPED TO 25MPH.THIS HAPPENED 3 TIMES DURING WEEK OF 3/14/16 AND AGAIN ON 3/22/16. HAD TO MAKE DEFENSIVE EMERGENCY MANEUVER TO STEER THE CAR AWAY FROM THE TRAFFIC LANES AND STOP ON THE SIDE OF THE FREEWAY. WAS ALMOST REAR ENDED BY A SEMI. CAR HAD TO BE TURNED OFF AND RESTARTED TO COME BACK TO NORMAL DRIVING MODE. CAR WAS TAKEN TO MERCEDES DEALER AND IT WAS DIAGNOSED TO BE A BAD TORQUE CONVERTER CAUSING THIS LIMP MODE. DEALER REPAIRED THE CAR BY REPLACING THE TORQUE CONVERTER. THERE WAS NO CHECK ENGINE LIGHT. WHEN THE DEALER HOOKED UP THEIR COMPUTER THERE WERE CODES FOR BAD TORQUE CONVERTER.
2012 MERCEDES S550. CONSUMER STATES VEHICLE SLID BACKWARDS IN PARKING LOT *TGW THE CONSUMER STATED THE SAFETY ISSUE WAS REGARDING THE VEHICLE BEING PUT IN THE NEUTRAL POSITION AFTER TURNING OFF THE ENGINE. THE CONSUMER STATED THREE WEEKS AGO, HE HAD THE MISFORTUNE OF PARKING HIS VEHICLE IN A PARKING LOT. WITHOUT OPENING THE DOOR, HE TURNED OFF THE ENGINE AND WHEN HE REMOVED HIS FOOT FROM THE BRAKE, THE VEHICLE SLID BACKWARDS AND HIT ANOTHER VEHICLE. BOTH VEHICLES WERE DAMAGED. THE CONSUMER STATED THE MINUTE THE ENGINE IS TURNED OFF, THE VEHICLE SHOULD BE PUT IN THE ELECTRONIC PARKING POSITION, RATHER THAN NEUTRAL.*JB
Complaints are unverified consumer reports submitted to NHTSA. A high complaint count may reflect vehicle popularity, not defect severity. Data sourced from NHTSA public records.
Data synced from NHTSA on Apr 25, 2026