— A Mercedes C300 wrist pin problem caused the owner of a 2015 Mercedes-Benz C300 to petition federal safety regulators to investigate claims of damaged M274 engines.
The petitioner alleges the Mercedes M274 engines fail due to piston damage from wrist pins that are the wrong size.
According to the owner who filed the April 2022 petition with the National Highway Traffic Safety Administration to open a safety defect investigation, his 2015 Mercedes C300 lost power while driving on the highway.
The car was shaking with white smoke pouring from the exhaust with an odor of burnt oil. A dealership diagnosed the problem as a cracked piston.
The Mercedes-Benz C300 wrist pin petition alleges all Mercedes models equipped with variations of the M274 engine should be investigated based on Mercedes technical service bulletin (TSB) LI03.10-P-060916 (SB-10058545-4447).
The Mercedes wrist pin TSB was issued in July 2015 regarding the M274 engine, but no specific models were named.
"Due to unfavorable tolerance of piston wrist pin, resulting in knocking, clattering/rattling noises, causing an enlarged end float connecting rod in piston, from crank assembly of engine when cold. No model or years listed." — TSB LI03.10-P-060916
The 2015 Mercedes-Benz C300 owned by the petitioner is equipped with a 2.0L M274 DE20LA engine calibrated to run on 91 octane or higher gasoline and contains diamondlike coating (DLC) wrist pins.
NHTSA says only the 2015 Mercedes C300 will be included in the evaluation to determine if a formal investigation should be opened into an estimated 93,000 cars.
