2014 — 2018
2.0L M274 DE20 AL - C250
Petrol
Scan for cylinder misfire codes and check for sudden power loss under load. | Observation: Watch out for engine shaking or low cylinder pressure; the M274 engine has a catastrophic design flaw involving 1st/2nd piston cracking or wrist pin failure due to LSPI, which completely destroys the cylinder wall and requires a total engine replacement.
Listen closely to the engine on a cold start and monitor cranking time. | Observation: Listen for a sharp metallic rattling sound lasting 2-5 seconds; the M274 camshaft adjusters and internal signal gear plates slip out of alignment, causing timing synchronization failure, extended cranking, and eventual non-start.
Inspect front suspension upper and lower control arms over speed bumps. | Observation: Listen for squeaking or clunking noises; the aluminum-heavy W205 front suspension and multi-link control arm hydro-bushings split prematurely, ruining wheel alignment and tearing inner tyre treads rapidly on NZ roads.
Test the center console touchpad, click wheel, and scan for auxiliary battery failure. | Observation: Verify the infotainment COMAND controller functions without freezing, and check for the infamous 'Auxiliary Battery Malfunction' dash warning, which is caused by a failed voltage converter capacitor located in the passenger footwell.
Proactively replace the auxiliary battery voltage converter capacitor and check spark plugs early to mitigate the risk of engine pre-ignition/piston cracking.
Perform a mandatory transmission service (including the integrated plastic pan filter replacement if equipped with 9G-Tronic) and check for early camshaft adjuster play.
Replace the brittle plastic turbo coolant lines, thermal management vacuum actuators, and inspect the main electric water pump for cracks.
Strictly mandate oil changes every 8,000km to 10,000km maximum using specialized MB229.5/229.6 oil with high LSPI resistance to prevent piston failure.
Clean and lubricate the complex panoramic sunroof tracks quarterly to prevent the high-torque motor from stripping its fragile plastic gears and leaking water into the A-pillars.
Check for early signs of oil leaking from the crankcase ventilation (PCV) valve system, which is buried under the intake manifold and highly labor-intensive to replace.
Ensure matching high-performance premium tyres are fitted and cross-rotations are performed frequently to counter the W205's aggressive factory front camber wear.
Verify the main AGM battery health status, as modern W205 SAM modules and electronic steering racks draw massive current and trigger phantom electronic gremlins under low voltage.
Estimated repair costs if issues arise
The absolute worst-case scenario for M274 owners. If a piston cracks due to factory design flaws, independent Euro shops in NZ will charge massive sums for a salvaged engine swap or a complete custom short-block rebuild.
Frequent M274 failure. Requires replacing both the intake and exhaust camshaft adjusters with updated Mercedes-Benz part numbers, along with a new timing chain tensioner and valve cover gaskets.
W205 Airmatic bellows leak and the air compressor burns out trying to compensate. Replacing failed OEM air bags with high-quality aftermarket equivalents (like Arnott) is mandatory to restore ride height.
Noticed something inaccurate or missing?Suggest an edit→
Disclaimer: This report is generated with the assistance of AI analysis based on verified automotive data. While we strive for 100% accuracy, enthusiasts should always conduct physical inspections and consult service records. View Full Disclaimer