C-Classbuyer's guide

The W205 C-Class is the cheapest way into a current-generation Mercedes — and the easiest way to take on someone else's repair bill. Timing chain wear on the M274, 9G-Tronic conductor plate failure, and AdBlue faults on the diesels are the three patterns that decide whether this car is a bargain or a mistake. This guide walks you through the checks before you pay a deposit.

This guide covers ten documented issues: timing chain and wet-belt service risk (M274 / OM651 / OM654), 9G-Tronic and 7G-Tronic shudder and conductor plate faults, AdBlue, DPF and EGR emissions faults, coolant leaks and water-pump failure, COMAND infotainment and software electrical faults, suspension knocks and uneven tyre wear (Airmatic where fitted), brake corrosion and electronic parking brake faults, panoramic roof and boot water leaks, ADAS radar and camera calibration after windshield work, and the full recall and campaign checklist. Each fault has a field check and a real repair-cost range.

A serviced, documented W205 is a quietly excellent used car. An undocumented one will eat its value in the first year of ownership. This guide tells you which one is in front of you.