5.1. General information
In this part of Chapter 2 the order of performance of such works as dismantle of the power unit from the car and major maintenance of details of the internal device of considered engines is in detail considered. Recommendations about check of a condition of various details have the general character.
Major maintenance of the engine - general comments
It is not always easy to come to a conclusion about expediency of complete major maintenance of the engine as it is necessary to be based on a number of objective indicators.
Big run is not a sufficient indicator of need of carrying out major maintenance, on the other hand, small run does not exclude need of carrying out major maintenance. The most important indicator most likely is timeliness of the current maintenance of the engine. At timely change of oil and the filter, and also at performance of all other necessary works on service, the engine serves reliably throughout many thousand kilometers of run. On the contrary, insufficient on volume or untimely maintenance can be at the bottom of sharp reduction of a resource of the engine.
The raised consumption of oil indicates wear of the piston rings, directing plugs of valves and maslosjemny caps. It is necessary to be convinced that leaks are not at the bottom of the raised consumption of oil, and only after that to draw a conclusion about unfitness of piston rings and directing plugs of valves. To define a probable cause of malfunction, measure a compression in engine cylinders (see section 2).
For scoping of the forthcoming works check a compression in engine cylinders (see section 4). Carry out also tests by means of the vacuum gage and define character of indications of this device (see section 3).
Check pressure of oil a manometer screwed to the place of the sensor of pressure of oil and compare result of check to standard value. If pressure of oil low, the reason can be wear of radical and shatunny bearings or details of the oil pump.
Capacity loss, "failures" in operation of the engine, a detonation or the metal knocks, the increased noise from the gas-distributing mechanism, indicate the increased fuel consumption need of carrying out major maintenance, especially, if all these signs of abnormal work are shown at the same time. If performance of all adjustments does not lead to improvement, the unique means of elimination of abnormal operation of the engine is major maintenance. Major maintenance consists in restoration of details of the engine to a condition specified in specifications for the new engine. At carrying out major maintenance pistons and piston rings are replaced, chiseled or хоннингуются cylinders. After repair of cylinders which is carried out in a specialized workshop, installation of repair pistons is required. Shatunnye and radical loose leaves of the crankshaft, and also a cover of basic necks of a cam-shaft also are subject to replacement, if necessary follows прошлифовать crankshaft necks before restoration of normal gaps with shatunny and radical loose leaves. As a rule, valves, as their condition at the moment of repair as a rule not the absolutely satisfactory are subject to repair also. During major maintenance of the engine repair of such units as a starter, the generator and the ignition distributor also is carried out. As a result repaired engine should possess qualities of the new unit and sustain considerable run without refusals.
At major maintenance it is necessary to replace such important details of system of cooling as hoses, drive belts, the thermostat and the pump of cooling liquid. The radiator should be surveyed on tightness and purity of internal channels (see. Hl. 3). If you bought the repair engine, or the block of cylinders of an incomplete complete set, some suppliers do not give a guarantee on operation of these units without high-quality washing of a radiator. At major maintenance of the engine also it is recommended to replace the oil pump.
Before the beginning of major maintenance of the engine familiarize with the description - the corresponding procedures that there was an impression of the forthcoming amount of works and requirements to them. At observance of all norms and rules, in the presence of all necessary tools and adaptations, it is simply to execute major maintenance, considerable expenses of time however be required. Roughly not less than two weeks, especially are required if for repair and restoration of details it is necessary to address in a specialized workshop. Check existence of spare parts and in advance take care of acquisition of necessary special tools and the equipment. Almost all works can be executed by means of a standard tool kit though exact measuring devices will be necessary for check and determination of suitability of these or those details. Often check of a condition of details carry out in specialized workshops in which also receive recommendations about replacement or restoration of these or those details.
To address in workshops of car-care center follows only after complete dismantling of the engine and check of a condition of all details, especially the block of cylinders to solve which operations on service and repair will be carried out in workshops.
As the condition of the block of cylinders is defining factor of decision-making on its further repair or about purchase new (or repair) the block of cylinders, to buy spare parts or to carry out operations on machining of accompanying details follows only after careful check of its technical condition. Make it a rule that the true price of repair is time, - then it is not necessary to pay for installation of the worn-out or restored details.
In summary we will note that assembly of any units should be carried out with all care in a pure room to avoid further failures of the repaired engine and to provide its reliable work.
Engine diagnostics by means of the vacuum gage
Measurement of depression is reliable and rather cheap way of diagnostics of the engine. According to indications of the vacuum gage it is possible to receive idea of a condition of piston group, of tightness of laying of a head of the block of the cylinders which are soaking up and final collectors, correctness of adjustments of a power supply system of the engine and production of exhaust gases, capacity of exhaust gases, a condition of valves (their zalipaniye or a burn-out) and springs of valves and also to check correctness of adjustment of the moment of ignition and preservation of phases of a gazoraspredeleniye at operation of the engine.
Unfortunately, indications of the vacuum gage are difficult for interpreting and results of the analysis of indications can be erroneous therefore, vacuum diagnostics is expedient for uniting with other methods.
Initial factors on which indications of the vacuum gage are analyzed and the most exact conclusions about an engine condition become, absolute instrument reading and nature of movement of an arrow of the device (dynamics of indications) are. A scale of the majority of vacuum gages проградуирована in mm. рт. column. In process of depression increase (and respectively pressure drop) instrument reading increases. On each 300 m above sea level absolute indications of the vacuum gage will differ approximately on 25 mm Hg.
Attach the vacuum gage directly to a soaking-up collector (To cm, a photo), but not to other openings through which the vacuum, by the channel of a certain length separated from a collector (for example, to openings before a butterfly valve) is created.
Before the beginning of tests completely warm up the engine. Block wheels and put the car on the hand brake. At position of the lever of gear shifting in neutral situation (or in the situation Park on cars with automatic transmission) start the engine and leave to idle.
Before engine start carefully check a condition of blades of the fan (existence on them of damages or cracks). In operating time of the engine do not bring a hand too close to the fan, hold the device on sufficient removal from the fan and do not stand on one line with a rotating krylchatka.
Check the vacuum gage indication. On the serviceable engine the vacuum gage should show depression of 430-560 mm Hg, and the arrow of the device should be almost motionless.
Below the description of character of indications of the vacuum gage and a technique of definition of a condition of the engine on their basis follows.
1. Too low level of depression usually indicates on not tightness of laying between a soaking-up collector and the chamber of a butterfly valve, a vacuum hose, and also too late ignition or for the wrong moment of opening and closing of valves. Before removing covers of a gear belt and to check combination of adjusting labels check ignition installation by means of a stroboscope and eliminate all other possible reasons, being guided by the techniques of check described in the present Chapter.
2. If vacuum gage indications on 75-200 mm Hg are lower normal and are unstable (the arrow twitches), it indicates a leak in laying on an entrance of a soaking-up collector or on malfunction of a nozzle.
3. If the arrow regularly deviates on 50-100 mm Hg, the reason is not tightness of valves. For confirmation of this conclusion check a compression in engine cylinders.
4. The arrow irregularly deviates towards low indications, or shaking shows low depression. A probable cause is the increased resistance to movement of valves, or interruptions in operation of cylinders. Check a compression in cylinders and examine candles.
5. If idling the arrow quickly fluctuates within 100 mm Hg, and operation of the engine is accompanied by a smoke from the exhaust silencer, directing plugs of valves are worn-out. For check of this conclusion it is necessary to carry out tests of chambers of combustion for tightness (with an air rating). If the arrow quickly fluctuates and the increase in turns of the engine is at the same time observed, it is necessary to check tightness of laying of a soaking-up collector, elasticity of springs of valves. Such indications also can be caused by a burn-out of valves and interruptions in operation of cylinders (ignition failures).
6. Weak fluctuations of an arrow (within 20-30 mm Hg in both parties) indicate unstable work of ignition. Check all provided installations and adjustments, if necessary connect to the engine the analyzer of system of ignition.
7. At big fluctuations of an arrow check a compression in cylinders, or carry out tests for tightness as causes of defect can be the idle cylinder, or violation of tightness of laying of a head of cylinders.
8. If instrument readings slowly change in a wide range, check purity of pipelines of system of compulsory ventilation of a case, correctness of adjustment of gas mixture, tightness of laying of the case of a butterfly valve, or soaking-up collector.
9. Sharply open a butterfly valve and when turns of the engine will reach 2500 rpm release a zaslonka. Zaslonka should come back to a starting position slowly. Indications of the vacuum gage should fall almost to zero, then increase and exceed the control indications corresponding to stationary idling approximately on 125 mm Hg then depression should be restored at former level. If depression is restored slowly, and at sharp opening of a zaslonka excess of the control indication is absent, wear of piston rings can be the reason. At the slowest restoration of depression check purity of a final path (as a rule the exhaust silencer or the catalytic converter). The simplest way of such check consists in disconnection of an exhaust path before a suspicious site and in test repetition.