8.1.2. Failure diagnostics of AT - the general information

Refusals of AT most often happen for one of the following five reasons: decrease in efficiency of return of the engine, violation of adjustments, malfunctions of hydraulics, mechanical damages, or failures of the onboard processor / its alarm chain. Failure diagnostics always has to begin with the simplest checks: estimate the level and a condition of ATF (see the Head Routine maintenance), check adjustment of a cable of management of gear shifting and the sensor switch of provision of transmission. Further, carry out trial runs of the car for the purpose of definition of efficiency of the made corrections. If it was not succeeded to fix a problem, it is necessary to drive away the car on car repair shop for more detailed diagnostics with use of the special equipment. The description of some of symptoms of refusals of AT see Diagnostics of malfunctions of knots and systems of the car.


Primary checks

 PERFORMANCE ORDER

  1. Warm up transmission up to the normal working temperature during a short trip.
  2. Check the ATF level (see the Head Routine maintenance):
    • If liquid is obviously not enough, make the corresponding adjustment, having added necessary quantity ATF is fresher. Be convinced of correctness of the carried-out adjustment according to indications of the measuring probe, then check transmission for existence of signs of external leaks (see below);
    • If level is too high, merge surplus of ATF, then check it for existence of traces of presence of cooling liquid, the testifying violation of tightness of the internal partitions of a radiator separating its heat exchanger from side tanks with ATF (see the Head of the Cooling system and heating);
    • If ATF is made foam, empty transmission and fill it with fresh liquid — merged check for existence of traces of presence of cooling liquid.
  3. Check installation of turns of idling of the engine.

If the engine not as it should be, it is not necessary to start performance of primary checks of transmission until the corresponding corrections are made.

  1. Check freedom of movement of a cable of the drive of a butterfly valve.
  2. Check draft of a cable of management of gear shifting (see Adjustment of the drive of switching of AT), make sure of correctness of adjustment and freedom of its movement.


Diagnostics of leakages of ATF


General information

The majority of leaks easily come to light at visual check. Repair usually consists in replacement of the corresponding defective epiploon or laying. If it is not possible to reveal a leak source during external survey, act as it is described below.

First of all it is necessary to exclude probability of a mistake in definition of the nature of leak. It is not necessary to confuse ATF to motive oil or brake fluid (transmission liquid usually has dark red color).

 PERFORMANCE ORDER

  1. For identification of a source of leak make short (several kilometers) a trip, then park the car over the outspread blank sheet of a cardboard. Later a couple of minutes the source of leak can be revealed in the wake of the liquid dripping on a cardboard.
  2. Attentively examine the suspected site and the surface surrounding it, paying special attention a joint of the interfaced pro-masonry surfaces. For the purpose of expansion of a viewing angle use a pocket mirror.
  3. If it is not possible to reveal a leak source still, carefully wipe the surface of the suspected site with the rags moistened with solvent, then dry it.
  4. Make one more short trip, this time often changing the speed of the movement, then again examine the cleaned suspected site.

After identification of a source of leak it is necessary to define and remove the cause of its development, and only then to pass to performance of necessary recovery work. Replacement of the damaged laying will not result in desirable result if to leave not eliminated the defect of the interfaced surface which led to a laying exit out of operation. So, the deformed flange needs to be aligned.

In the following subsections the most typical reasons of development of leakages of ATF and a condition which have to be executed that there was no recurrence are listed.

Part cannot be executed from the listed requirements without use of the special equipment. In this case the car should be driven away on car repair shop.


Leaks through pro-masonry surfaces

Periodically examine a cover on the right side of a transmission case. Check existence on the places and reliability of tightening of fixing bolts, you watch that on a cover traces of mechanical damages did not appear.

Through a cover excessively hard tightening of fixing bolts, damage of a sealing surface of a case of transmission, laying destruction, and also emergence of cracks or porosity of walls of a case are among the possible reasons of development of leaks. If laying of a cover or case of transmission is formed by a sealant pillow, the probability of the wrong choice of type of the last is not excluded.


Leaks through epiploons and cuffs

The most typical reasons of an exit of epiploons of transmission excessively high ATF level, violation of passability of a ventilating sapun, mechanical damage of walls of a landing nest, damage actually out of operation are among an epiploon, or the wrong installation of the last. Also the probability of damage of a pin of the shaft passed throughout an epiploon, or an excessive side play of the last as a result of wear of bearings is not excluded.

Check a state and correctness of landing of a sealing cuff of the directing tube of the measuring probe. Periodically examine on existence of signs of leaks a surface around an arrangement of a driving gear wheel of a speedometer or the sensor of the speed (VSS). In case of need you make replacement of a sealing ring.


Leaks through defects in transmission case walls

Formation of cracks or time in a transmission case body can be the reason of development of leakages of ATF. Consult with specialists of car service.

Check tightness of nipple knots of connection of hoses of a cooler of ATF.


Leaks through сапун and a jellied mouth

Leaks through сапун or a jellied mouth can happen owing to excessive filling of transmission, hit in ATF of cooling liquid, violation of passability of a sapun or returnable openings.