It should be noted that despite the real possibility of overhaul without removing the engine of such assemblies as the connecting rod and piston group, this type of work usually cannot be performed as some independent operation. To repair the crank and other mechanisms, as a rule, some additional measures should be taken (obligatory, for example, is the cleaning of parts and flushing of oil channels). For this reason, such work is included in the list of basic engine overhaul procedures.
Engine description
Engine 2.0L (1998 cm/cube) refers to the SR series installed on Nissan vehicles.
The engine is a 16-valve, overhead valve, four cylinders in a row and two camshafts. The engine is located across the axis of the car, in front of it. The transmission is installed on the left side of the engine.
Crankshaft 5-support. The axial play of the crankshaft is regulated by the selection of thrust half rings installed next to the upper liner of the middle (3rd) main bearing.
Connecting rod bearings consist of two shells inserted into the connecting rod and into the connecting rod cap parallel to the crankshaft axis. The connecting rods are connected to the pistons by means of fingers, which are installed with an interference fit in the connecting rod head and secured in the piston by spring retaining rings. The pistons are cast from aluminum alloy, there are three rings on the pistons - two compression and one oil scraper.
The cylinder block is cast iron, cylinders are bored inside the block. On engines of the type in question, cylinder bores are sometimes called "dry cases".
The intake and exhaust valves are closed by coil springs and move inside guide bushings pressed into the cylinder head along with the valve seats. In case of increased wear, the seats and bushings can be pressed out independently of each other and replaced with new ones.
The camshafts are chain driven and control 16 valves via levers. The levers are mounted directly below the camshafts. Valve clearances are adjusted automatically by hydraulic devices. The lower bearings of the camshaft journals are beds bored in the tides of the cylinder head.
The engine is lubricated by an oil pump driven by the crankshaft toe. The oil passes through an oil receiver with a coarse filter and through a fine filter screwed into the cylinder block, from which it is directed through the lubrication channels inside the cylinder block and crankcase to the crankshaft main bearings and to the camshaft bearing journals. The connecting rod bearings are lubricated under pressure through holes inside the crankshaft, and the camshaft bearing journals are also lubricated under pressure. Camshaft cams, valve stems and other engine parts are splash lubricated. Some models have an oil cooler designed to keep the oil temperature constant under extreme engine operating conditions.