Gasoline engines — general information about repair (Peugeot 406)

This section describes repair operations that can be performed on the engine while it is installed in the vehicle. If repairs are being performed on an engine that has already been removed, the removal operations can be ignored.

Description of the ZU engine

The engine has four cylinders and is mounted transversely at the front of the car. The clutch and gearbox are located on the left side of the engine.

The crankshaft rests on five main bearings. Thrust half rings are installed on the second main bearing.

The lower heads of the connecting rod have liners. The pistons are attached to the connecting rods with piston pins. On the 2.0-liter engine, the piston pins are installed on a sliding fit in the connecting rods and secured with retaining rings. On all other models, there is a fixed fit in the connecting rod. The pistons are made of aluminum alloy and have three piston rings, two sealing rings and one oil scraper ring.

On aluminum engine cylinder blocks, the cylinder block is of the "wet liner" type. Replaceable cylinder liners are installed on top of the cylinder block, and sealing is performed at the base of the liner by a circular cross-section sealing ring.

On engines with a cast iron cylinder block, the engine has a conventional "dry liner" type. The cylinders are made directly in the cylinder block material and can only be bored out during engine repair.

On all models, the camshaft drives a timing belt and controls eight valves (1.6 liter models) or sixteen valves (1.8 and 2.0 liter models) via tappets located under the camshaft lobes. On 1.6-liter models, valve clearances are adjusted by shims that are installed between the tappets and the upper end of the valve stem; on all other models, the valve clearances are self-adjusting due to hydraulic tappets. The camshaft is located in the bearing caps, which are bolted to the top of the cylinder head. The valves are closed by springs that press the valve plate against the seat. The valve seats and guides are replaceable.

The coolant pump is driven by a toothed belt and is located on the right side of the cylinder block.

The engine is lubricated under pressure created by an oil pump, which is driven by (through the chain and sprocket) from the right end of the crankshaft. Oil is sucked through a mesh filter located in the oil receiver and then flows through an externally mounted filter into the cylinder block channels. From there, the oil flows to the crankshaft (main bearings) and camshaft. The lower connecting rod head bearings are supplied with oil through internal drillings in the crankshaft; the camshaft bearings are also supplied with oil under pressure. The camshaft cams and valves are lubricated with sprayed oil, as are all other moving parts of the engine.

An oil cooler is installed on some models to maintain constant oil temperature under heavy operating loads. The oil cooler is installed behind the oil filter and is cooled by coolant from the engine cooling system.

Engines are identified not only by their displacement, but also by their engine code. The engine code consists of three letters (for example: BFZ). The code is stamped on a plate attached to the front left side of the cylinder block, or stamped directly on the front side of the cylinder block, to the left of the oil filter.

Repair operations that can be performed on the engine installed in the vehicle: