4.1. General information and preparatory operations
The description of the most typical and important procedures of service and repair of engines, behind an exception, the demanding special skills and tools is provided in this chapter, such as procedures of capital repairs of the engine – these works should be charged to specialists of car service. Below petrol M60/1, M60/2 and M73 engines, and also diesel M57 and M67 engines are considered. Works on M51, M52 and M62 engines are made similarly; information on repair of these engines is provided in the Guide No. 149 of the ARUS series to car repairs of BMW of the 5th series from 1996 to 2001 to the issue.
On the considered cars engines of six types are installed: 6-cylinder turbodiesel of M51 (SOHC), 6-cylinder diesel M57 (DOHC), 6-cylinder petrol M52 (DOHC) engine, 8-cylinder V-shaped petrol (M60, M62) and diesel (M67) engines (DOHC), and also 12-cylinder V-shaped petrol M73 (SOHC) engine. Abbreviations of SOHC and DOHC indicate presence of respectively one or two camshafts on a number of the cylinders (and, therefore, 2-x or 4-x valves on the cylinder) located in the top part of the engine. The power unit is installed along the car and is removed from a motive compartment by means of the crane up.
Its head and the block of cylinders of the M52 engine are cast from aluminum alloy. Unlike traditionally applied cast iron aluminum alloy has higher heat conductivity and smaller weight. It promotes the best cooling and lower fuel consumption.
The block of cylinders of the turbodiesel M51 engine is cast from cast iron, a head of cylinders – from light alloy. At the increased wear and existence of zadir on walls of walls of cylinders they can be honingovat with the subsequent replacement of old pistons by pistons of the repair sizes.
The head of cylinders at all engines has a so-called cross purge. It means that fuel mix comes to cylinders on the one hand, and the fulfilled gases (FG) come out with another. Such scheme promotes more bystry gas exchange.
The GRM drive is carried out from a bent shaft through a chain; for the drive of auxiliary units multiridge belts are used. M52 engines are equipped with system of adjustment of phases GRM (VANOS) by means of the shift of the inlet camshaft concerning its asterisk. Adjustment of phases GRM the control unit of the engine (ECM, DME) depending on the speed of a bent shaft by means of opening and closing of the special oil valve operates.
Valves are set in motion from camshafts through hydraulic pushers. Need of adjustment of valvate gaps in the course of maintenance is absent. On SOHC engines inlet and final valves are given from one shaft, and on DOHC engines the separate camshaft is intended for the drive of inlet and final valves.
But the piston are 2 compression and one oil scraper ring. The bent shaft is located in radical bearings.
Supply of oil in the lubrication system is carried out by the oil pump which at the 6-cylinder petrol engine settles down in front in the pallet of a case and is given from a bent shaft. At the diesel M51 engine the oil pump is in a cover of a chain of the GRM drive and is given via the tooth gearing. Oil is sucked in from the pallet of a case and through openings and pipelines moves to bearings of cranked and distributive shaft, and also to the working surfaces of cylinders.
The pump of cooling liquid is located in a forward part of the block of cylinders. From a pump shaft via the viscous coupling at achievement of the corresponding temperature the cooling fan is given. The drive of the water pump is carried out through a multiridge belt which at the same time gives the generator. The cooling system is filled with antifreeze mix, a security measure from corrosion and water with the low content of lime.
Preparation of air-fuel mix is controlled by system of injection which together with system of ignition and some other systems is a part of a control system of the engine. Thanks to it the stable low content of harmful substances in the fulfilled gases is provided. The system of ignition has no mobile elements that excludes their wear. At the diesel engine distribution of fuel on cylinders is regulated by an electronic control unit (ECM, DDE).
Petrol engines are calculated for work on AI-95 gasoline, however thanks to existence of detonation regulation also other grades of fuel can be applied. If AI-98 gasoline is used, then under normal conditions operation fuel consumption is cut and engine capacity increases. When using AI-91 gasoline engine capacity decreases and fuel consumption increases.
Before holding any procedures of service of the engine make cleaning of a motive compartment and the external surfaces of the power unit with use of special solvent. Such processing will allow to avoid hit of dirt in the engine.
In case of need, the forthcoming work determined by character, it is possible to remove a cowl for the purpose of ensuring freedom of access to the components which are subject to service (see the Head Kuzov). In order to avoid casual damage of a paint and varnish covering cover car wings with special covers or old blankets.
The excessive consumption of motive oil can be considered a signal of need of conducting check of a condition of piston rings, maslootrazhatelny caps and/or the directing plugs of valves. Naturally, first of all, it is necessary to make sure that losses of oil are not connected with development of its external leaks. Check a compression in cylinders (see the Section Check of Compression Pressure) to define the general condition of the engine.
Loss of the developed power, violation of stability of turns, excessive noise of the valvate mechanism and the increased fuel consumption usually are rather characteristic signs of need of performance of capital repairs of the engine, in particular, when all these factors are shown at the same time. If performance of a full range of settings does not help with elimination of problems, carrying out the general mechanical works on restoration of the engine will be the only way out.
Capital repairs of the power unit mean restoration of all its working parameters to the level characteristic of the new engine. During capital repairs replacement of piston rings and restoration of mirrors of cylinders (a pro-point and/or a honingovaniye) is without fail made. Replacement of radical and conrod bearings of a bent shaft is usually carried out, the pro-point and restoration of his necks can be in case of need made. Service of valves which condition at the time of emergence of need for performance of capital repairs of the engine almost for certain leaves much to be desired is without fail carried out. In parallel with carrying out the general repair of the power unit also recovery repair of a starter and the generator is usually made.
Such critical components of the cooling system as hoses, driving belts and the thermostat when carrying out capital repairs of the engine have to be replaced with new without fail. Besides, it is necessary to check attentively a condition of a radiator (see Chapters of Control and routine maintenance of the car and Cooling system of the engine, heating, ventilation and conditioning). In case of identification of signs of development of leaks or violation of passability the radiator should be replaced. Do not forget to check a condition of the oil pump also.
Capital repairs of the engine do not demand from the performer of high vocational training, however take away a lot of time. It is necessary to plan refusal of use of the car for the term of not less than two weeks, in particular in need of the request for the help in a mechanical workshop for the purpose of performance of separate recovery work.
The most part of works can be executed with use of usual set of the metalwork tool, however some of checks by definition of suitability of separate components to further use demand use of the precision measuring equipment. In doubtful situations ask for the help experts HUNDRED.
Do not forget that in a question of expediency of performance of capital repairs of the engine the condition of the block of its cylinders is decisive factor. Frequent cheaper and more reliably it appears to replace the worn-out engine restored.
In conclusion it is possible to notice that all efforts on performance of recovery repair of worn-out components will be spent for nothing at the negligent relation to the requirement of respect for purity at assembly of the unit.