Before you buy a used Renault Modus / Grand Modus.

Look out for: Engine knocking, especially when cold; low oil pressure; at worst, engine failure.

Ask them to check: Listen to the engine from cold, measure oil pressure and check the oil-change history. If it knocks, do not keep driving.

Look out for: Injection warning, jerking, rough idle, loss of power, smoke and sometimes a no-start.

Ask them to check: Read the codes (e.g. P0087, low rail pressure) and look for filings in the diesel filter. If the circuit is contaminated, replace pump, rail and injectors and clean the tank and lines.

Look out for: Noise or squeal around the belts; if the timing belt breaks, the engine stops suddenly and can be badly damaged.

Ask them to check: Keep to the timing-belt interval and always replace the full kit (belt, rollers and pulleys); check the auxiliary belt and its pulley.

Look out for: Uneven idle, jerks when accelerating, lack of power or the engine going into limp mode, sometimes with the engine warning light on.

Ask them to check: At the workshop: read the codes with diagnostic equipment (EOBD P0400 to P0404 or P0172; Renault DF077, DF084 or DF241), test the valve electrically and its opening with the engine warm, and find where the oil comes from (breather, turbo, level). Pierburg advises against cleaning it, as it can be damaged: it is replaced if faulty, and an engine ECU update sometimes solves it.

Look out for: Noise on start-up on older 1.6s: a failing camshaft phaser; central locking that locks and unlocks by itself (moisture); a Quickshift automated gearbox with faults and a broken hydraulic gearchange piston; on early 1.5 dCi, a sticking EGR (rough running or turbo damage); if the battery is replaced or disconnected, the power steering loses its coding.

Ask them to check: Listen on a cold start; test the locking and the Quickshift gearbox; after a battery change, have the steering recoded at the garage.

Look out for: While driving a warning light comes on and the assistance is lost all at once: the steering wheel gets heavier and heavier at low speed.

Ask them to check: Drive carefully, because without assistance you need much more force on the wheel, and ask the garage for a steering code read-out. If the visual and electronic check confirms the fault, the repair is a new steering column. A car that has already been repaired has a blue label on the front left suspension turret.

Look out for: Hard to start or will not start, stalls, loses power or jerks; sometimes air bubbles show in the clear fuel pipe.

Ask them to check: At the workshop, in this order: look for air and leaks in the low-pressure circuit and prime it; check the fuel filter bowl for metal swarf (if there is any, the whole injection system is replaced); measure the rail pressure, the IMV regulator's resistance (4.8–5.8 Ω) and each injector's return flow (25 ml at most in the test). A new injector's code must be written into the ECU.