: The M278 engine often develops leaks from the plastic turbo coolant lines, which should be upgraded to aluminum, and oil seepage on the back of cylinder heads.
: The CLS550's signature air ride is prone to failure, particularly the air springs and compressor. Replacing a single air strut at a dealership can cost $2,500–$3,200 , while a full system overhaul can exceed $8,000 . buy mercedes cls550
: In pre-facelift models (2012–2014), the timing chain tensioner and lack of check valves are major weaknesses. A cold-start "rattle" is a warning sign of imminent failure, which can require an engine-out job costing thousands. : The M278 engine often develops leaks from