1.6. Diagnostics of malfunctions of knots and systems of the car

The owners of cars performing procedures of routine maintenance of the vehicle it agrees the schedule provided in the Head Routine maintenance will be extremely seldom forced to address materials of this section. Reliability of the knots and components installed on modern cars is so high that at timely performance of replacement of the materials of details which are worn out and failed as a result of aging the probability of their sudden refusal is extremely small. Refusals seldom happen spontaneously and usually are a consequence sometimes of long development of defect. In particular, failure of mechanical components practically is always preceded by emergence and development of the characteristic symptoms which are shown sometimes for many thousands of kilometers of a run to the full. The same components which can fail unexpectedly usually are not vital for functioning of the main knots and systems of the car, or are easily replaced in road conditions.

Fundamental step at identification of the reasons of any refusal is the choice of a point of the beginning of searches. Often the reason is lying on a surface, however in certain cases it is necessary to work, making small investigation. The motorist who produced half-dozens of casual checks of replacements and corrections quite has chance to find a cause of failure (or its symptom), however it is impossible to call such approach reasonable, in view of its labor input and aimlessness of expenses of time and means in any way. There is a quiet logical approach to search of the failed knot or component much more effectively. Surely it is necessary to take into account everything preceding breakage, sometimes insignificant, symptoms and the guarding signals, such as loss of the power developed by the engine, change of indications of measuring instruments, emergence of unusual sounds and smells, etc. Do not forget that failure of such components as safety locks or spark plugs can be only a symptom more deeply of the hidden violation.

In this subsection rather simple scheme of diagnostics of the most often found refusals is given below. The reasons of violations and their symptoms are grouped in a sign of the relation to functioning of any concrete unit or system: "Engine", "Cooling system", etc. In brackets references to the corresponding Chapters and sections of the Management concerning functioning of the components suspected of malfunction are given.

Regardless of the refusal nature investigations of its reason are always taken the identical basic principles as a principle:

Make sure of correctness of definition of symptoms of refusal. Told means confidence in delimitation of the area of searches that it is especially important with the help in refusal diagnostics to other motorist who cannot adequately state symptoms of the violation taking place.

Try not to miss obvious violations. For example, if the engine is not started, do not hesitate to check availability of fuel in a gasoline tank (at the same time it is not necessary to take on trust statements of the owner of the faulty car). In case of refusal electric equipments first of all it is necessary to check a state and reliability of fastening of terminal connections of an electrical wiring, only after it it makes sense to get diagnostic units.

Try to remove a cause of failure, but not its symptom. Replacement of the discharged battery new will help to make start of the engine, however the reason of a discharge of the old battery taking place will remain not eliminated that will lead to bystry failure and new. Also replacement of the spark plugs thrown by oil will allow to restore serviceability of functioning of the engine for some time, however the refusal by all means will soon repeat (if the reason lay not just in application of candles not of that type).

Do not take on trust any statements. Remember that the "new" component can also be faulty, in particular if it long time lay in a luggage carrier — it is not necessary to exclude a component from the list checked only for the reason that it is new or is recently established. In case of neglect it is not necessary to be surprised with implementation of this recommendation when the cause of failure established, at last, is lying on a surface from the very beginning.


Failure diagnostics and reasons of decrease in efficiency of return of the engine


The engine is not turned in attempt of its start


The engine is turned, but not started


Start of the cold engine is complicated


Start of the hot engine is complicated


Input of a starter in gearing is complicated, or is followed by extraneous noises


The engine is started, but at once becomes deaf


During the parking under the engine are formed begin to flow oils


Stability of turns of idling is broken


Admissions of ignition on single turns take place


Admissions of ignition take place at the movement on transfer


Idling turns are excessively high


The battery does not "hold" a charge


The control lamp of an ignition / charge continues to burn at the working engine


The control lamp of an ignition / charge does not light up at turn of a key in position of ON


Admissions of ignition take place during the movement


Stability of turns of the engine is broken during acceleration


The engine works with breakthroughs at the accelerator pedal withheld not movably


The engine spontaneously becomes deaf


The power developed by the engine fell


There are "shots" in a final path


The engine works with breakthroughs at the accelerator pedal withheld not movably


During acceleration or at increase in load of the engine there are knocks caused by too early ignition or a detonation


The engine continues to work after switching off of ignition (diesel effect)


Pressure drop of motive oil takes place


The consumption of motive oil is excessive


Fuel consumption is excessive


Fuel leak (in salon and near the car distinctly smells of gasoline) take place


Different noise arising during the operation of the engine

In certain cases elimination of knock is helped by filling of the engine with oil with higher component of viscosity.


Diagnostics of malfunctions of the cooling system


The engine overheat takes place


Overcooling takes place


External leak of cooling liquid takes place


Internal leak of cooling liquid takes place

Existence of internal leaks is confirmed by the presence of cooling liquid at motive oil causing emulsification of the last.


Losses of cooling liquid take place


Circulation of cooling liquid is broken


Corrosion development takes place


Diagnostics of malfunctions of AT

In view of complexity of a design of AT it will be difficult to average amateur mechanic to carry out enough precisely diagnostics of its refusals and recovery repair. In case of problems, excellent from listed below, the owner of the car should ask for the help specialists of car service. It is also not necessary to hurry with demontazhy faulty transmission as its many checks are made by in situ (on the regular place).


Leakages of ATF

ATF usually differs in dark red color. It is not necessary to confuse traces of its leaks to those from motive oil (the last can communicate on a transmission case the running air stream).

For identification of a source of leak, first of all, it is necessary to clear a case of transmission and surfaces surrounding it of dirt and lubricant. Use qualitative degreaser or execute steam cleaning of the unit. Make on the car a short trip with a low speed of the movement (that traces of the leak taking place did not communicate far from its source). The car also establish to Poddomkratta it on props. Examine a transmission case, visually revealing leakage sources of ATF.

Most often act as those:


ATF has brown color or smells of ashes


There is no automatic switching of transmission to a low gear at full squeezing of the accelerator pedal


The engine is started in the provision of transmission, excellent from "Р or "N"


Transmission "comes off" the chosen situation, switches hardly or with noise, or does not provide progress of the car forward or back

There is a set of the possible reasons listed refusals however only one of them - violation of the ATF level gets to the sphere of competence of the average amateur mechanic. Check, in case of need make adjustment level / replacement of liquid and the filter, in parallel check a condition of ATF. In all other cases the car should be driven away for diagnostics and recovery repair / replacement of transmission on car repair shop.


Diagnostics of malfunctions of the driveshaft


Leaks in a forward part of the driveshaft take place


At transfer inclusion (at the time of emergence of loading) there is a knock


Vibrations take place

First of all check balancing of wheels and pressure of a rating of tires.


The scraping sound takes place


Takes place howl or whistle


Diagnostics of malfunctions of the back bridge and main transfer


The extraneous noise identical at the movement on transfer and a setup takes place


The knock arising at start-off from the place or at gear shifting takes place


Foreign sounds arise during commission of turns


Vibrations take place


Oil leak takes place


Diagnostics of malfunctions of the transfer case


Gear wheels jump out from gearing


Switching of the modes is complicated


Extraneous noises take place


Diagnostics of malfunctions of the brake system

Before coming to conclusion about failure of the brake system, check a state and pressure of a rating of tires, uniformity of loading of the car and the angles of installation of forward wheels.


When braking course stability of the car is broken


During braking there are extraneous noises (a gnash or high-frequency squeal)


The course of a brake pedal is excessively big


Softness of the course of a brake pedal at its squeezing takes place


The stop of the car requires applying of excessively big effort to a brake pedal

See the reasons listed in the previous subsection plus the following:


The pedal of a foot brake fails to a floor without resistance


During braking there are pulsations of a pedal of a foot brake


Brake pedal pulsations take place during sharp braking


During braking there is a vibration transferred to a brake pedal or a steering wheel


Brakes "are taken" (efficiency of return of the engine is reduced, wheels are excessively warmed during the movement)


Back wheels are blocked at normal braking


Back wheels are blocked at emergency brake application


The parking brake does not hold the car properly


Diagnostics of malfunctions of a suspension bracket and steering

Before starting checks of components of a suspension bracket and the steering drive make sure that the wrong rating of tires, installation of tires of various standard size, violation of balancing of wheels, or "prikhvatyvaniye" of brakes is not a cause of infringement.


Course stability of the car is broken


The side play of wheels and the increased vibration of the car takes place


During commission of turns and when braking there is "galloping" and/or rocking of the car


Roving or the general course instability of the car takes place


Excessively hardly the steering wheel turns


The side play of a steering wheel is excessive


There is no hydraulic strengthening


Serviceability of return of a steering wheel to rectilinear situation is broken


The steering wheel rotates in different directions with various resistance


The steering pump works with the increased noise


The extraneous noises proceeding from a forward part of the car take place


During braking controllability of the car worsens


The car excessively sank


The gnash or other extraneous noises published by the steering mechanism takes place


Excessive wear of tires takes place


The increased wear of an internal or external part of a protector


Scaly wear (obtrepyvaniye) of a protector


Wear of the central part of a protector


Wear of the inner and outer edges of a protector


Uneven wear of a protector