Description of the ZU engine
Four-cylinder engine mounted transversely at the front of the vehicle. The clutch and gearbox are located on the left side of the engine.
The crankshaft is supported by five main bearings. Thrust half rings are mounted on the second main bearing.
Liners are installed in the lower heads of the connecting rod. The pistons are attached to the connecting rods with piston pins. On the 2.0 liter engine, the piston pins are mounted in a sliding fit in the connecting rods and secured with circlips. On all other models - a fixed fit in the connecting rod. The pistons are made of aluminum alloy and have three piston rings, two seals and one oil scraper.
On aluminum engine blocks, the cylinder block is of the type "wet liner". Replaceable cylinder liners are mounted on top of the cylinder block and sealed at the base of the liner with an O-ring.
On engines with a cast-iron cylinder block, the engine has a conventional type "dry liner". The cylinders are made directly in the material of the cylinder block and can only be bored when repairing the engine.
On all models, the camshaft drives the timing belt and controls eight valves (1.6 liter models) or sixteen valves (1.8 and 2.0 liter models) through the pushers located under the camshaft cams. On 1.6 liter models, valve clearances are regulated by gaskets that are installed between the pushers and the upper end of the valve stem; on all other models, valve clearances are self-adjusting by means of hydraulic tappets. The camshaft is located in bearing caps that are bolted to the top of the cylinder head. The valves are closed by springs that press the valve disc against the seat. Seats and valve guides are replaceable.
The coolant pump drives the timing belt and is located on the right side of the cylinder block.
The engine is lubricated under pressure from an oil pump driven by (through chain and sprocket) from the right end of the crankshaft. The oil is sucked in through a strainer located in the oil receiver, and then flows through an externally installed filter into the channels of the cylinder block. From there the oil goes to the crankshaft (main bearings) and distributor. The connecting rod bearings are supplied with oil through internal bores in the crankshaft; oil is also supplied under pressure to the camshaft bearings. Camshaft cams and valves are lubricated with sprayed oil, as are all other moving parts of the engine.
An oil cooler is fitted on some models to keep the oil temperature constant under heavy operating loads. The oil cooler is mounted 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 (ex: 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 car:
- compression pressure check;
- Removal and installation of a cover of a head of the block of cylinders;
- removal and installation of the crankshaft pulley;
- removal and installation of a casing of a gear belt of a drive;
- removal and installation and adjustment of the toothed belt tension;
- removal and installation of the toothed belt tensioner;
- replacement of elements of the camshaft lubrication system;
- replacement of the camshaft and pushers;
- checking and adjusting valve clearances;
- removal and installation of the cylinder head;
- cleaning of the cylinder head and pistons;
- removal and installation of the oil pan;
- removal, inspection and installation of the oil pump;
- replacement of crankshaft oil seals;
- removal and installation of the gearbox;
- removal, inspection and installation of the flywheel;
- removal and installation of an oil cooler.