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 capital repairs of details of the internal device of the considered engines in detail is considered. Recommendations about check of a condition of various details have the general character.
Capital repairs of the engine - general comments
It is not always easy to come to a conclusion about expediency of complete capital repairs of the engine as it is necessary to be based on a number of objective indicators.
The big run is not a sufficient indicator of need of carrying out capital repairs, on the other hand, the small run does not exclude need of carrying out capital repairs. 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 when performing all other necessary works on service, the engine serves reliably throughout many thousands of kilometers of a run. On the contrary, insufficient on volume or untimely maintenance can be the reason of sharp reduction of a resource of the engine.
The raised consumption of oil indicates wear of piston rings, the directing plugs of valves and oil scraper caps. It is necessary to be convinced that leaks are not the reason of the raised oil consumption, and only after that to draw a conclusion about unfitness of piston rings and the 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 oil pressure the manometer screwed to the place of the sensor of pressure of oil and compare result of check to standard value. If oil pressure low, then can be the cause wear of radical and conrod bearings or details of the oil pump.
Loss of power, "failures" in operation of the engine, a detonation or metal knocks, the increased noise from the gas-distributing mechanism, the increased fuel consumption indicate the need carrying out capital repairs, especially, if all these signs of abnormal work are shown at the same time. If performance of all adjustments does not lead to improvement, then the only means of elimination of abnormal operation of the engine are capital repairs. Capital repairs consist in restoration of details of the engine to the state specified in specifications for the new engine. When carrying out capital repairs pistons and piston rings are replaced, cylinders are chiseled or honningutsya. After repair of cylinders which is carried out in a specialized workshop installation of repair pistons will be required. Connecting and radical rods of the crankshaft, and also cover of basic necks of a cam-shaft are also subject to replacement, if necessary it is necessary to proshlifovat crankshaft necks before restoration of normal gaps with connecting and radical rods. As a rule, also valves as their state at the time of repair as a rule not absolutely satisfactory are subject to repair. During capital repairs of the engine repair of such units as a starter, the generator and the distributor of ignition is also carried out. As a result the repaired engine has to have qualities of the new unit and sustain a considerable run without refusals.
At capital repairs it is necessary to replace such important details of the cooling system 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, then some suppliers do not give a guarantee for operation of these units without high-quality washing of a radiator. At capital repairs of the engine it is also recommended to replace the oil pump.
Before capital repairs of the engine study the description - the corresponding procedures that there was an impression of the forthcoming amount of works and requirements to them. At respect for all norms and rules, in the presence of all necessary tools and devices, it is simple to execute capital repairs, however considerable costs of time will be involved. Approximately 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 think of acquisition of necessary special tools and the equipment. Almost all works can be performed by means of standard tool kit though precision measuring instruments will be necessary for check and definition of suitability of these or those details. Often check of a condition of details is carried out in specialized workshops in which also receive recommendations about replacement or restoration of these or those details.
It is necessary to address in workshops of car service only after full dismantling of the engine and check of a condition of all details, especially the block of cylinders to solve what operations on service and repair will be carried out in workshops.
As the condition of the block of cylinders is the defining factor of making decision on its further repair or about purchase new (or repair) the block of cylinders, it is necessary to buy spare parts or to carry out operations on machining of the accompanying details 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 conclusion we will note that assembly of any units should be carried out with all care in the pure room to avoid further failures of the repaired engine and to ensure its reliable functioning.
Diagnostics of the engine 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 gain an impression about a condition of piston group, about 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, the capacity of exhaust gases, a condition of valves (their sticking 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 gas distribution during the operation of the engine.
Unfortunately, it is difficult to interpret indications of the vacuum gage and results of the analysis of indications can be wrong therefore, it is expedient to unite vacuum diagnostics with other methods.
Initial factors on which indications of the vacuum gage are analyzed and draw the most exact conclusions about a condition of the engine, absolute instrument reading and the nature of the movement of an arrow of the device (dynamics of indications) are. The scale of the majority of vacuum gages is graduated in mm. рт. column. In process of depression increase (and according to 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 the soaking-up collector (Cm, a photo), but not to other openings through which vacuum, is created by the channel of a certain length separated from a collector (for example, to openings before a butterfly valve).
Before tests completely warm up the engine. Block wheels and put the car on the emergency brake. At position of the lever of gear shifting in neutral situation (or in situation Park on cars with automatic transmission) start the engine and leave to idle.
Before start of the engine carefully check a condition of blades of the fan (existence on them of damages or cracks). In operating time of the engine you do not bring a hand too close to the fan, you hold the device on sufficient removal from the fan and do not stand on one line with the rotating krylchatka.
Check the indication of the vacuum gage. On the serviceable engine the vacuum gage has to show depression of 430 - 560 mm Hg, and the arrow of the device has to be not mobile almost.
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 not tightness of laying between the soaking-up collector and the camera of a butterfly valve, a vacuum hose, and also too late ignition or for the wrong moment of opening and closing of valves. Before uncovering a gear belt and to check combination of adjusting tags check installation of ignition by means of a stroboscope and remove all other possible causes, being guided by the check techniques described in the present Chapter.
2. If indications of the vacuum gage are 75 - 200 mm Hg lower than normal and are unstable (the arrow twitches), then it indicates a leak in laying on an entrance of the soaking-up collector or on malfunction of a nozzle.
3. If the arrow regularly deviates on 50 - 100 mm Hg, then not tightness of valves is the reason. For confirmation of this conclusion check a compression in engine cylinders.
4. The arrow irregularly deviates towards low indications, or shaking shows low depression. The increased resistance to the movement of valves, or interruptions in operation of cylinders is a probable cause. 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 followed by smoke from the muffler, then the directing plugs of valves are worn-out. For check of this conclusion it is necessary to carry out tests of combustion chambers for tightness (with an air rating). If the arrow quickly fluctuates and increase in turns of the engine is at the same time observed, then it is necessary to check tightness of laying of the soaking-up collector, elasticity of springs of valves. Such indications can be also caused by a burn-out of valves and interruptions in operation of cylinders (failures of ignition).
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 the analyzer of system of ignition to the engine.
7. At big fluctuations of an arrow check a compression in cylinders, or carry out tests for tightness as can be causes of defect the idle cylinder, or violation of tightness of laying of a head of cylinders.
8. If instrument readings slowly change in the wide range, then 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 the soaking-up collector.
9. Sharply open a butterfly valve and when turns of the engine reach 2500 rpm release the gate. The gate has to come back to a starting position slowly. Indications of the vacuum gage have to reduce almost to zero, then increase and exceed the control indications corresponding to stationary idling approximately on 125 mm Hg then depression has to be restored at the previous level. If depression is restored slowly, and at sharp opening of the gate excess of the control indication is absent, then wear of piston rings can be the reason. At extremely slow restoration of depression check purity of a final path (as a rule the muffler or the catalytic converter). The easiest way of such check consists in disconnection of an exhaust path before the suspicious site and in test repetition.