The light, magnesium cased MQ200 and the MQ250, sized for higher torque, are the most widespread manual gearboxes in the transverse engine VAG models. Both have the same two weak points, and both depend on use.

The EGR valve and its cooler block up with soot and oily deposits; the particulate filter cannot regenerate on short urban trips. The signs are reduced power, a warning light, and frequent regeneration. The software update after the diesel emissions affair made the EGR operate more often, which accelerated the phenomenon: the maker gave goodwill repairs in several cases.

On this engine the water pump is driven by the timing belt, and the plastic impeller of the pump, along with its electronically controlled shut-off ring, is the weak point: the ring sticks, and the impeller separates from the shaft or disintegrates. The first sign is slowly disappearing coolant and heating that stays cold for a long time. The real risk is not the price of the pump: the leaking water washes the grease off the timing belt rollers, and from then on the belt is what fails. If the timing belt snaps, the engine is badly damaged inside. That is why the two are always replaced together.

The internal springs of the flywheel tire, and the two discs knock against each other. The signs are a rattling or knocking from the bellhousing at idle and when releasing the clutch pedal, and vibration through the floor. If the clutch slips without a burnt smell, that also points to the flywheel. It is worth replacing in time: a disintegrated flywheel can destroy the bellhousing too. At a clutch replacement the two go together anyway.

The two weak points of the cooling system are the radiator and the heater matrix. The latter is inside the cabin: if it leaks, you get a sweet antifreeze smell, the windscreen mists up greasily from inside, and damp stays under the passenger side carpet. The damp goes unnoticed for a long time under the floor covering. And replacing the heater matrix means stripping the dashboard.

The vanes of the variable geometry turbo are glued together by soot and oil arriving through the EGR. First you get overboost or a lack of boost, then loss of power above 2,000 rpm, and finally limp mode. Caught in time it is enough to remove the turbo, clean it and fit a new actuator rod. Short urban trips and gentle, low rev driving speed up the deposits.

The Caddy has leaf springs at the back, because it was designed to carry loads, and that is exactly the part that tires from the way it is used. The sign of a tired spring is that the back of the car sits down even unladen (the rear wheel "sinks" into the arch), and a dull clonking or knocking is audible from the rear over bumps. The spring mount and the trailing arm bushes make the same noise. On a heavily loaded fleet car it is effectively a wear item; and a tired rear suspension wears the tyre unevenly too.

The Caddy sliding door is opened many times a day, and the lower roller carries the weight of the door. That is what wears first: the door is hard to start moving, it grinds, it sticks halfway, and finally it "drops". The door gap visibly differs at the top and the bottom. If the mounting of the guide rail works loose, the door presses against the body, and a rub mark is left on the paint. If the roller is not replaced, the hinge and the bodywork are damaged too. On a version with a sliding door on both sides, check both.