Before you buy a used Mercedes-Benz Clase E (W211).

Look out for: Rattle for 2–3 seconds or more on a cold start; engine light for camshaft timing deviation.

Ask them to check: Listen to a cold start, read timing fault codes and check the chain replacement history.

Look out for: Engine light with P0016 and P0017 (1200 and 1208 on Mercedes diagnostics), rattle on start-up, hesitation, misfires and, in severe cases, stalling.

Ask them to check: Compare the engine serial number with the 2729..30 468993 cut-off, read cam correlation codes and, if in doubt, inspect the sprocket with a borescope. First rule out the cam adjuster magnet (a cheap fault).

Look out for: Puffing or “chuffing” at idle, a diesel smell under the engine cover and a hard black crust around the injectors; power loss from sooted intake flaps or turbo.

Ask them to check: Remove the engine cover and look for black residue around the injectors, listen at idle and check the intake flaps.

Look out for: Oil pooling in the engine's V, burning oil smell, drips under the engine; or a hiss or chirp next to an injector with an exhaust smell.

Ask them to check: Visual inspection of the engine's V and the base of the injectors.

Look out for: Coolant loss, coolant in the oil or white smoke (broken head bolts); rattle or ticking on start-up (camshaft and lifter wear).

Ask them to check: Overnight cooling system pressure test, oil analysis and camshaft inspection with a borescope.

Look out for: Gearbox stuck in 2nd or 3rd (limp mode), harsh shifts, delay engaging D or R, gearbox warning often without an engine light; turning off and restarting clears it for a while.

Ask them to check: Diagnose with Xentry/STAR to see the sub-codes (a basic reader only shows P0700). Check for oil in the gearbox connector.

Look out for: One corner sags overnight, suspension fault warning, the compressor runs a lot or a compressor overheated message appears; eventually the car sits low and rides hard.

Ask them to check: Spray soapy water on bellows, lines and valve block; read each corner's data with Xentry; check the compressor fuse and relay. Do not replace the compressor without fixing the leak first, or the new one will fail soon.

Look out for: Red messages in the cluster such as “STOP VEHICLE”, “Brake defective” or “Reduced braking power – visit workshop”, a hard pedal or little assistance, and pump noises when braking or opening the door. In a complete failure only the front wheels brake, using foot force alone.

Ask them to check: With any red brake warning, stop driving and call for assistance. At a Mercedes dealer: read the SBC control unit with official diagnostics, check open recalls and warranty extensions by VIN, and change the brake fluid only with the procedure SBC requires. The cycles-exhausted warning means replacing the unit, not clearing the code.

Look out for: Oil around the electrical connector on the side of the gearbox, harsh shifts or slipping, delayed engagement and limp mode: the car stays in one gear (usually 2nd and reverse after a restart) and the engine light comes on.

Ask them to check: Read the gearbox control unit codes before switching off if possible (a restart can clear them). Look for oil at the connector and, with it unplugged, on its pins and at the control unit plug. According to the service bulletin, the connector should only be removed with gearbox oil below 50 °C to avoid damaging the conductor plate, and the harness must be routed without tension.