2008 Mercedes-Benz S550

I’m reporting a serious safety issue with the balance shaft sprocket in my Mercedes-Benz S550 (M273 engine, 273.968). This is a known defect that causes the sprocket to wear out far too early due to poor material design. When it wears, it throws off the engine timing, leading to check engine lights, rough idling, reduced power, and even stalling. In some cases, the engine can shut down while driving, which is a major safety risk. Thousands of people have experienced this exact problem, and it’s all over Mercedes forums, Reddit, and technical bulletins. Mercedes quietly updated the part in later models, which shows they knew the early ones were defective. Some people got repairs under warranty or “goodwill,” but most of us are stuck with thousands in repair bills for something that clearly shouldn’t have failed. This isn’t just a mechanical issue—it’s a safety concern. Imagine merging onto a highway or turning through an intersection when the engine loses power. That’s a real risk with this defect. Mercedes should be held accountable, and NHTSA needs to investigate and push for a recall before someone gets hurt or worse.

NHTSA ID

11659570

Incident

Mar 1, 2025

The contact owns a 2008 Mercedes-Benz S550. The contact stated while driving 40-50 MPH, the vehicle was shuddering intermittently. The contact stated that the failure recurred while at a complete stop. The check engine warning light was illuminated. The contact stated that the failure had been recurring intermittently. The vehicle was taken to an independent mechanic, where it was diagnosed that the wiring harness was causing an engine misfire. The mechanic related the failure to an unknown recall. The dealer was notified of the failure. The manufacturer was notified of the failure and referred the contact to the NHTSA Hotline for assistance. The failure mileage was approximately 40,000.

NHTSA ID

11577423

Incident

Mar 14, 2014

Mileage

40,000 mi

We were traveling home and our TPMS indicated a tire failure. The PSI starting dropping rapidly. We took the tire off and found that only 4 " of rubber holding the back sidewall together on the tire. I then inspected the other tires on the car (which were purchased and installed at the same time) are showing signs of failure as well. All of the tires are 255-40-r19 We had a family of 4 in the vehicle at the time of the incident.

NHTSA ID

11547224

Incident

Sep 28, 2023

The contact owns a 2008 Mercedes-Benz S550. The contact stated while driving 35-40 MPH, the message "SAFETY" was temporarily displayed on the instrument panel. Additionally, the contact stated while starting the vehicle on several occasions, the message " SAFETY " was displayed on the infotainment system screen. The check engine warning light was illuminated, and the messages "Active Head Lamp Inoperative" and "Service Required. Do Not Shift Gears" were displayed. The contact also stated that upon shifting into drive (D), the gear shift indicator displayed that the transmission was in park (P). The contact stated that the vehicle failed to shift into the intended gear and had become undrivable. An independent mechanic replaced the battery; however, the failure persisted. The mechanic informed the contact that the computer needed to be reset. The vehicle was not repaired. The used car dealer was notified of the failure. The Mercedes-Benz dealer and manufacturer were not notified of the failure. The failure mileage was approximately 176,310.

NHTSA ID

11541256

Incident

Jul 14, 2023

Mileage

176,310 mi

TL* THE CONTACT OWNS A 2008 MERCEDES-BENZ S550. THE CONTACT STATED THAT WHILE STOPPED, THE VEHICLE WAS SUDDENLY REAR-ENDED CAUSING THE VEHICLE'S DRIVER AND PASSENGER FRONT SEAT HEAD REST AIR BAGS TO DEPLOY. THE CONTACT STATED THAT HE SUSTAINED BROKEN BONES IN HIS NECK AS WELL AS INJURIES TO HIS LEFT ELBOW AND BACK AREA. THE FRONT PASSENGER RECEIVED INJURIES TO HIS NECK AND BACK AREA AND WAS TRANSPORTED THE HOSPITAL BY AMBULANCE WHILE THE DRIVER DROVE HIS VEHICLE TO THE HOSPITAL. A POLICE REPORT WAS FILED. THE VEHICLE WAS TAKEN TO A LOCAL A BODY SHOP POST INCIDENT WHO REPAIRED THE BUMPER AMONGST OTHER PARTS OF THE REAR OF THE VEHICLE. THE VEHICLE WAS THEN TOWED TO THE DEALER (MERCEDES-BENZ OF WAPPINGERS FALLS (134 OLD POST RD, WAPPINGERS FALLS, NY 12590 PHONE: (845) 298-0600) WHO PERFORMED THE HEAD REST AIR BAGS REPLACEMENT, AS WELL AS, ELECTRICAL AND OTHER REPAIRS DUE TO THE COLLISION. THE MANUFACTURER WAS MADE AWARE AND OPENED A CASE REGARDING THE MATTER. THE CONTACT WAS CONCERNED WITH THE FORCE OF THE HEAD REST AIR BAGS DEPLOYMENT. THE APPROXIMATE FAILURE MILEAGE WAS 78,013. *DR*JB

NHTSA ID

11329607

Incident

Mar 25, 2018

Mileage

78,013 mi

P-RC-200808004 BODY CONTROL ACCELERATION SENSORS...MODELS 2001-2008 11/4/2008 - 200807001 RE-CODE THE SOFTWARE CALIBRATION NUMBER (SCN) 11/04/2008 - 200803005 REPLACE FRONT SAM S-SC-2012070002 RETROFIT ADAPTER WIRING HARNESS ON CAMSHAFT ADUSTMENT SOLENOIDS MODELS 2005-2011 S-RC-200807001 REVISION TO STEP Z, IN WORK PROCEDURE RECODE THE SOFTWARE CALIBRATION NUMBER (SCN). *TR

NHTSA ID

11324288

Incident

Feb 11, 2012

Mileage

148,000 mi

EVEN CHANGE TO NEW TIRES, THE AIR PRESSURE UP TO 37 AND ALWAYS AFTER 1 WEEK OR SO, DOWN TO 33, COMPLAIN AND CHANGE TIRE AND STILL HAVE THE SAME RESULT. YOU COULD ONLY CHECK THE TIRE PRESSURE AFTER YOU RUN FOR A WHILE. MASSAGE CHAIR, AFTER OPERATION AND ALL THE SUDDEN IT STOP. CLOCK IN THE CABIN DOESN'T CHANGE EVEN YOU SET IT UP AND THE INTERNAL SAID THE RIGHT TIME AND THE FRONT DOESN'T CHANGE

NHTSA ID

11292448

Incident

Jan 1, 2018

Mileage

69,000 mi

MY VEHICLE HAS A STRONG GAS ODOR WHILE DRIVING BUT PARTICULARLY WHEN THE VEHICLE IS STATIC OR PARKED. THIS SMELL IS SO STRONG THAT I CANNOT SIT IN THE CAR AND MY CLOTHES REAK OF THE SMELL. THERE HAS NOT BEEN ANY EXTERNAL GAS LEAKAGE OR PERFORMANCE ISSUES WITH THE CAR. ONLY THE GAS ORDOR THAT HAS GIVEN ME A HEADACHE AND MAKES ME NAUSEATED. THE CAR ONLY HAS 70,000 MILES ON IT.

NHTSA ID

11164448

Incident

Aug 1, 2018

Mileage

70,000 mi

Single throttle lift-off clunking noise from the side shaft when moving off (audible at the outboard end). The noise is heard once in each instance when changing direction of travel. Note: Sound file in attachment Cause If the complaint is eliminated by experimentally loosening the outboard collar nut (by 1 turn), the problem is due to cracking of the microweld between the wheel bearing inner race and the joint housing of the side shaft. Note: The collar nut must always be replaced after being loosened. See also LI33.20-P-078406 Remedy Coat contact surface of side shaft with wheel bearing with Molykote paint. To do this, proceed as follows: 1. Remove side shafts 2. Clean contact surface A (see image file in attachment "Outer joint housing before") before coating with Molykote, using "spirit" (free of dust and grease) 3. Coat contact surface A (see image file in attachment "Outer joint housing after") with Molykote and leave to dry for "one hour" in removed condition 4. Reinstall side shafts Note: Before using the antifriction coating (Molykote), stir it or shake it thoroughly for (at least 1 minute).

Complaint After successful commissioning of the HERMES control unit (N112/9) with XENTRY Diagnosis DVD 03/2026, the message "SOS - service not activated" appears on the instrument cluster. In addition, the following two conditions are also met: • HERMES (N112/9) control unit: event code B15CE00 is ACTIVE and STORED (A+S) • Vehicle Documentation System: For the HERMES control unit, the EID1, EID2, ICCID, IMEI, IMSI, TELNR fields in the "Identification/Serial number" column have the value "-" Cause Still under analysis Remedy Recommission the HERMES control unit (N112/9) with XENTRY Diagnosis 03/2026 and add-on 33399 installed or carry out the procedure with a newer version of XENTRY Diagnosis: XENTRY→ "N112/9 - Control unit for telematics services (HERMES)" -> "Adaptations" -> "Control unit commissioning" -> "Commissioning of previously installed control unit"

Complaint There are several types of complaint about noises or poor windshield wiper wiping performance: A: Wiper blades squeaking, chattering, shuddering B: The windshield is not wiped completely (streaking) C: During the downward movement water is pulled back onto the windshield from the A-pillar (Figure 1) D: After windshield cleaning, water keeps spraying onto the windshield for several wipe cycles (Figure 2) A1: The windshield and wiper blades are contaminated with residues from car washing facilities, identifiable by the water beading. The resulting differences in the friction values between the wiper blades and the windshield can excite the wiper blades to vibrate. Note: It is mostly wax residue from the washer system, but also water-repellent nano-particle coating for paint and/or silicone-based washer fluid, that could cause this problem. A partially dry windshield also has different friction values, which can likewise result in squeaking of the wiper blades A2: The wiper blades are worn by mechanical damage (wiper lip damaged by ice or insect debris, or deformed by long periods of disuse). A3: Incorrect angle of incidence of the wiper arms to the windshield. Because of this, the rubber lip of the wiper blade may not flip over at the reversal point. Cause B: B1: Wax/ dirt residues on the windshield B2: Wiper blades deformed or worn B3: Downforce of wiper arm not OK (Figure 3) Cause C: Water is pulled back onto the windshield by the differential pressure created as the wiper arm moves downwards. Cause D: Washer water collects in the fastening of the wiper blade and is blown onto the windshield by the airstream over several wipe cycles. Note and supporting information: Wiper blades are wear parts which, even when "not used" for long periods (kept in park position), may become permanently deformed and damaged. Further stresses on the rubber wiper blade arise due to various environmental influences which progressively change the effectiveness of the rubber wiper blade and accelerate the aging process. Due to the natural aging process and wear, the wiper blades should be replaced twice a year, preferably in Spring and Fall (see operator's manual). Remedy Remedy A: A1: Cleaning entire windshield with A 000 986 40 71. A2: Checking water's flow behavior after windshield has been cleaned (see Video 1). If, after cleaning, there are still areas with water beading, then the cleaning process must be carried out again until a rejection reaction is no longer present. • Note: On the vehicle in the video (Video 1), water still beads on the bottom left of the windshield. The windshield is still not properly clean, even though it appears to be clean. The windshield is only properly clean when there are no more areas on the windshield where water beads. A3: Replace wiper blades with genuine wiper blades. Important: Only exchange wiper blades if windshield no longer has water-repellent areas Note: Replacement of wiper blades is not covered under warranty and can be replaced at the expense of the customer. Remedy B: B1: Clean windshield with intensive cleaner A 000 986 40 71. Important: Do not clean the wiper blades otherwise the graphite coating will be damaged. B2: Replace wiper blades with genuine wiper blades • Note: Replacement of wiper blades is not covered under warranty and can be replaced at the expense of the customer. B3: Check the wiper arm for excessive resistance in the bearing. Restore mobility or replace wiper arm if necessary. Remedy C: Problem inherent in design for which there is no technical remedy. Exception: X204 up to 02/2014. In these vehicles, it is possible to install the design configuration of vehicles as of 02/2014. This includes wiper arms (styled arms) with improved behavior in this respect. It is also necessary to replace the wiper blades because the styled arms feature a Top Lock connection (previously Side Lock).

Complaint Headlamp, front fog lamp leaky or fogged. Cause Fogging of the headlamps is a natural phenomenon, which can occur under certain climatic conditions. It does not lead to any technical impairment of the headlamp. If a pressure compensation diaphragm is fitted in the housing cover, then the lamp unit is a "closed system". Remedy Headlamp: Remedy 1 Clearing fogged/condensed LED headlamps: 1. Drive vehicle into workshop (temperature higher than +18 °C/+64.4 °F) and connect the exhaust extraction. Note: Do not perform an engine wash before the defogging test. 2. Switch off the engine and connect battery support via a charger. 3. Open the hood. 4. Switch on the lights. 5. Leave the vehicle in this state for 60 minutes. 6. Check for formation of condensation, a significant reduction in the formation of condensation must be clearly recognizable (thawing progress). Clearing of fogged/condensed LED headlamps and LED rear lamps on electric vehicles: 1. Drive the vehicle into the workshop (temperature higher than +18 °C/+64.4°F). 2. Connect battery backup via a charger. 3. Open the front-end flap and ensure sufficient ventilation. 4. Switch on the lights. 5. Leave the vehicle in this state for 60 minutes. 6. Check for formation of condensation, a significant reduction in the formation of condensation must be clearly recognizable (thawing progress). Clearing fogged/condensed halogen/xenon headlamps: 1. Drive the vehicle into the workshop (temperature higher than +18 °C/+64.4°F). Note: Do not perform an engine wash before the defogging test. 2. Switch off the engine. 3. Open the hood. 4. Switch off the lights. 5. Leave the vehicle in this state for 60 minutes. 6. Check for formation of condensation, a significant reduction in the formation of condensation must be clearly recognizable (thawing progress). Note: If there is no visible reduction in condensation, check the headlamp for malfunctions. (see Remedy 2) It is not physically possible to defog the headlamps completely. Fogging does not impair the operation or the service life of the headlamp. Note: Only implement Remedy 1 for model series 463 (from model year 2018) and model series 465. Remedy 2 A defective headlamp can be identified as follows: 1. Check the headlamp for external damage and that the cover caps and the diaphragm are correctly seated. 2. Check the electrical connectors of the plugs and pins. 3. Check for leak tightness according to LI82.10-P-078307. The test can only be conducted on headlamps. 4. If the headlamp or the rear lamp has any external damage, replace the component part in accordance with the WIS instructions. Note: External damage to the headlamp/rear lamp or faulty seating of the cover caps does not present a warranty or goodwill case. Note: With headlamps, it is possible to install desiccant packs if the problem occurs repeatedly. • Open ventilation system LI82.10-P-078302 • Closed ventilation system LI82.10-P-078304

Complaint Headlamp, front fog lamp leaky or fogged Cause Fogging of the headlamps is a natural phenomenon, which can occur under certain climatic conditions. It does not lead to any technical impairment of the headlamp. If a pressure compensation diaphragm is fitted in the housing cover, then the lamp unit is a "closed system". Remedy Headlamp: Remedy 1 Clearing fogged/condensed LED headlamps: 1. Drive vehicle into workshop (temperature higher than +18 °C/+64.4 °F) and connect the exhaust extraction. Note: Do not perform an engine wash before the defogging test. 2. Switch off the engine and connect battery support via a charger. 3. Open the hood. 4. Switch on the lights. 5. Leave the vehicle in this state for 60 minutes. 6. Check for formation of condensation, a significant reduction in the formation of condensation must be clearly recognizable (thawing progress). Clearing of fogged/condensed LED headlamps and LED rear lamps on electric vehicles: 1. Drive the vehicle into the workshop (temperature higher than +18 °C/+64.4°F). 2. Connect battery backup via a charger. 3. Open the front-end flap and ensure sufficient ventilation. 4. Switch on the lights. 5. Leave the vehicle in this state for 60 minutes. 6. Check for formation of condensation, a significant reduction in the formation of condensation must be clearly recognizable (thawing progress). Clearing fogged/condensed halogen/xenon headlamps: 1. Drive the vehicle into the workshop (temperature higher than +18 °C/+64.4°F). Note: Do not perform an engine wash before the defogging test. 2. Switch off the engine. 3. Open the hood. 4. Switch off the lights. 5. Leave the vehicle in this state for 60 minutes. 6. Check for formation of condensation, a significant reduction in the formation of condensation must be clearly recognizable (thawing progress). Note: If there is no visible reduction in condensation, check the headlamp for malfunctions. (see Remedy 2) It is not physically possible to defog the headlamps completely. Fogging does not impair the operation or the service life of the headlamp. Note: Only implement Remedy 1 for model series 463 (from model year 2018) and model series 465. Remedy 2 A defective headlamp can be identified as follows: 1. Check the headlamp for external damage and that the cover caps and the diaphragm are correctly seated. 2. Check the electrical connectors of the plugs and pins. 3. Check for leak tightness according to LI82.10-P-078307. The test can only be conducted on headlamps. 4. If the headlamp or the rear lamp has any external damage, replace the component part in accordance with the WIS instructions. Note: External damage to the headlamp/rear lamp or faulty seating of the cover caps does not present a warranty or goodwill case. Note: With headlamps, it is possible to install desiccant packs if the problem occurs repeatedly. • Open ventilation system LI82.10-P-078302 • Closed ventilation system LI82.10-P-078304

Complaint Headlamps leaking or fogged Cause The fogging of the headlamp is a natural phenomenon which can occur under certain climatic conditions. In contrast to a leaky headlamp, physical fogging does not result in a technical impairment of the headlamp. A leak test must be performed to determine if physical fogging exists or if the headlamp is leaky. Remedy In advance, observe LI82.10-P-078301 "Headlamp/front fog lamp leaky or fogged". 1. Prepare headlamp/check for external damage: For headlamps with a closed system • Check the headlamps for any external damage and check also for correct seating of the Gore-diaphragm/correct latching of the cover caps. • If the headlamp exhibits any external damage, replace the headlamp. For headlamps with an open system • Check the headlamps for any external damage and seal off the vent then make sure the cover caps are latched correctly into place. • If the headlamp exhibits any external damage, replace the headlamp. Note: A headlamp with external damage is not a warranty or goodwill case. 2. Leak test of headlamp with overpressure: Connect test adapter to pressure tester. (Figure 1) Check test adapter for leak tightness. To do so, connect plug and coupling (Figure 2) and apply a maximum overpressure of 30 mbar. • The pressure must remain constant. If the pressure does not remain constant, use a new adapter. Seal all the outlet openings using sealing compound and the given diaphragm with the plunger (Figure 3). (Figure 4) • Make allowance for the different headlamp variants here (there are different outlet openings). Check if the headlamp needs to be removed to gain access to the diagnostic socket on the headlamp housing. Plug the adapter onto the diagnostic socket on the headlamp housing. (Figure 5). Apply a maximum of 30 mbar overpressure to the headlamp housing. Note: If the maximum overpressure of 50 mbar is exceeded the headlamp seal will be damaged. • If a pressure drop of less than 10 mbar is measured within 30 seconds, the headlamp is tight and there is natural physical condensation• If a higher pressure drop than 10 mbar is measured within 30 seconds, the headlamp is leaky. Note: The leaky position can be localized with the aid of soap suds. Replace any leaky headlamps. Desiccant packs can be installed for headlamps that are not leaky. Observe the following documents for installation of desiccant packs: • LI82.10-P-078302 Fogged headlamp, desiccant pack installed - open ventilation system • LI82.10-P-078304 Fogged headlamp, desiccant pack installed - closed ventilation system