Citan W420

Everything that slows and stops the car.

You are here because: Squealing or grinding when braking, a soft or long pedal, a brake warning light, or pulling to one side under braking.

To quote this we need: Front or rear, and whether the car has the sports or AMG brake package — the disc diameter changes with it.

What holds the wheels to the car, absorbs the road, and points the car where you steer.

You are here because: Knocking over bumps, the car sitting low on one corner, wandering or heavy steering, uneven tyre wear, or an AIRMATIC warning.

To quote this we need: Whether the car is on steel springs or air suspension. On Mercedes this changes the part completely and it is the most common mis-order.

The engine itself — the moving parts, the timing, and everything that seals it.

You are here because: Rattle on start-up, rough running, a check-engine light, an oil leak, low compression, or a timing chain warning.

To quote this we need: The engine code. The same model year can carry two or three different engines and almost nothing crosses over.

Getting oil where it is needed and keeping it clean and cool.

You are here because: Oil leak, low oil pressure warning, oil in the coolant, or oil consumption between services.

To quote this we need: Engine code, and whether the car has an oil cooler — several Mercedes engines do and several do not.

Keeping the engine, gearbox and charge air at the temperature they are designed to run at.

You are here because: Overheating, losing coolant, a temperature gauge that climbs in traffic, a sweet smell, or a coolant warning.

To quote this we need: Petrol or diesel and the engine code. Radiators differ with the gearbox cooler and with air conditioning.

Storing fuel and delivering it to the engine at the right pressure.

You are here because: Hard starting, misfire, hesitation under load, a smell of fuel, a fuel pressure fault code, or poor economy.

To quote this we need: Petrol or diesel, and the engine code. Injectors are coded to the engine and often to the cylinder.

Carrying gases away and cleaning them enough to pass a test.

You are here because: Blowing exhaust, a rattle underneath, failed emissions at registration, a DPF or AdBlue warning, or limp mode.

To quote this we need: Engine code and whether the car is petrol or diesel. Emissions parts are the most engine-specific on the car.

Starting the engine, keeping it running and keeping the battery charged.

You are here because: Car will not start, slow cranking, a battery warning light, misfire under load, or electrics that drop out.

To quote this we need: Engine code, and whether the car has a stop-start system — the battery and alternator differ if it does.

Taking the power from the engine to the wheels.

You are here because: Harsh or delayed shifts, a clunk pulling away, vibration at speed, a transmission warning, or fluid on the floor.

To quote this we need: Gearbox code and whether the car is rear-wheel drive or 4MATIC. The 4MATIC parts are different and cost more.

The sensors the car reads and the modules that decide what to do about them.

You are here because: A warning light with no obvious fault, a fault code from a scan, windows or locks that stop working, or intermittent electrics.

To quote this we need: The fault code if a garage has scanned it. Many modules must be coded to the car after fitting — that is a job as well as a part.

Seeing and being seen — and on a modern Mercedes, one of the most expensive things to replace.

You are here because: A cracked or fogged light, a bulb out, condensation inside the unit, or a lighting fault on the dash.

To quote this we need: Whether the car is halogen, xenon or LED, and pre- or post-facelift. Lights change inside a generation more than any other part.

Cooling the cabin — which in this climate is not a comfort item.

You are here because: Air-con blowing warm, a smell from the vents, a compressor that will not engage, or weak airflow.

To quote this we need: Whether the car has rear climate control — the system is larger and the parts differ.

Panels, glass and trim — what an accident, a car park or the sun damages.

You are here because: Accident damage, a dent or rust, a knocked-off mirror, peeling trim, or a cracked screen.

To quote this we need: A photograph, the chassis code and the paint code. Paint code is on the data sticker; panels are usually supplied primed, not painted.

Everything inside the cabin, including the parts the Gulf sun destroys first.

You are here because: A cracked or sticky dashboard, a sagging roof lining, a broken switch or handle, worn seat bolsters, or a rattle from the trim.

To quote this we need: Trim colour and code from the data sticker. The same part is made in several finishes and they are not interchangeable to look at.

What a car needs at every service, and what a workshop gets through.

You are here because: A service is due, or the car is being prepared for passing and registration.

To quote this we need: Engine code and mileage. Service kits are cheaper bought together than line by line.

Complete assemblies from stripped cars, where a new part is not proportionate to the job.

You are here because: An expensive assembly has failed on an older car, or an insurance repair has to be done at a price that makes sense.

To quote this we need: Chassis number and a photograph. We will say plainly whether a part is new or used — a used part sold as new is not a saving, it is a problem later.