Most of the operations described in this chapter are based on the engine not being removed from the vehicle. Therefore, if the information presented here is used during a major engine overhaul, or when the engine is removed, many of the steps included in this chapter can be skipped.
Access to the engine compartment can be improved by removing the hood as described in chapter 11.
Engine Description
In this chapter, engines are identified by manufacturer letter code and by volume. Engine identification is given in Specifications.
Engines - liquid-cooled, single or dual camshaft, in-line four-cylinder with cast iron blocks and aluminum cylinder heads. All engines are mounted longitudinally at the front. The gearbox is mounted behind the engine.
The crankshaft has five bearings; the bearing half rings that determine the axial clearance are installed in the central bearing.
The camshaft is driven by a toothed belt from the crankshaft sprocket. The ADR, APT, APW, AFY, AEB and AJL engines have two camshafts in the head, the belt drives the exhaust camshaft, the intake camshaft is driven from the exhaust by a chain installed in the rear ends of the shafts. The chain is tensioned by a hydraulic tensioner, in the ADR, AFY and APT engines the hydraulic tensioner plays the role of a valve timing regulator for the intake camshaft.
On ADP, ADR, AFY, APT and APW engines the timing belt also drives the auxiliary shaft, which in turn drives the oil pump and (on some models) ignition distributor. The valves are driven from the camshaft cams by means of hydraulic tappets and the clearance in the drive is thus adjusted automatically.
The cylinder head contains one or two camshafts driven by a toothed belt, intake and exhaust valves closed by one or two springs. The valve guide bushings are pressed into the cylinder head. The camshafts act on the valves directly through hydraulic tappets supplied with oil through holes in the cylinder head.
All engines except AHL have a pump in the cooling system with a drive from the crankshaft by an auxiliary belt. On some models, the drive on the coca of the cooling system is carried out from the pulley of the power steering pump. On AHL engines, the cooling system pump is driven by the timing belt. The cooling system is described in detail in chapter 3.
The engine is lubricated under pressure by a pump driven by a chain from the crankshaft (AHL) or from an auxiliary shaft (ADP, ADR, APT, APW, AFY, AEB, AJL). The oil is sucked by the pump from the sump through the oil receiver and fed to the replaceable oil filter. From there, it is fed under pressure to the cylinder head to the camshaft supports and hydraulic tappets and to the engine crankcase, lubricating the crankshaft bearing journals, connecting rod journals, piston pins and cylinder walls. An emergency oil pressure sensor is screwed into the oil filter housing, which is triggered at a pressure of 1.4 bar. On AHL, APT, APW, AFY, AEB and AJL engines, an oil cooling unit is installed above the oil filter, washed from the engine cooling system. It serves to reduce the oil temperature before it is fed to the cylinder block.