Note. AT and CVT failures most often occur for one of the following five reasons: reduced engine efficiency, misadjustments, hydraulic malfunctions, mechanical damage, or failures of the onboard processor or its signal circuit. Failure diagnosis should always start with the simplest checks: check the level and condition of the ATF (see chapter Current service), check shift and kick-down throttle cable adjustment. Next, test drive the vehicle to determine the effectiveness of the corrections made. If the problem cannot be fixed, you should drive the car to a service station for more detailed diagnostics using special equipment. Some of the symptoms of AT/CVT failures are described in Diagnostics of malfunctions of nodes and systems of the car.
Primary Checks
1. Warm up the transmission to normal operating temperature for a short drive.
2. Check the ATF level (see chapter Current service):
a) If the liquid is clearly not enough, make the appropriate adjustment by adding the required amount of fresh ATF. Verify that the dipstick adjustment is correct, then check the transmission for signs of external leaks (see below);
b) If the level is too high, drain excess ATF, then check it for traces of coolant, indicating a leak in the internal radiator bulkheads separating its heat exchanger from the side ATF tanks (see chapter Cooling and heating systems);
c) If the ATF foams, empty the transmission and fill it with fresh fluid - check the drained one for traces of coolant.
3. Check the engine idle speed setting.
Note. If the engine is out of order, you should not proceed with the initial checks of the transmission until the appropriate corrections have been made.
4. Check for freedom of movement of the throttle control cable in kick-down mode (Integra models), make appropriate adjustments if necessary (see Seat adjustment).
Note. The cable can function
Note. It is normal to operate on a cold, stopped engine, which is not a guarantee of the correct operation of the engine when the unit is running and warmed up to normal operating temperature. Check the cable under various engine conditions.
5. Check shift cable pull (see Equipment and controls in the cabin), make sure that the adjustment is correct and that it can move freely.
Diagnosis of ATF leaks
1. Most leaks are easily identified by visual inspection. Repair usually consists of replacing a defective oil seal or gasket. If the source of the leak cannot be identified by visual inspection, proceed as described below.
2. First of all, the possibility of error in determining the nature of the leak should be excluded. ATF should not be confused with engine oil or brake fluid (transmission fluid is usually dark red in color).
3. Run a short test to find the source of the leak (several kilometers) ride, then park the car over a blank sheet of cardboard. After a couple of minutes, the source of the leak can be identified by traces of liquid dripping onto the cardboard.
4. Carefully inspect the suspected area and the surrounding surface, paying special attention to the joint of the mating gasket surfaces. In order to expand the viewing angle, use a pocket mirror.
5. If you still cannot find the source of the leak, carefully wipe the surface of the suspected area with a rag soaked in solvent, then dry it.
6. Drive another short drive, this time changing your speed frequently, then re-examine the cleaned suspect area.
7. After identifying the source of the leak, it is necessary to determine and eliminate the cause of its development, only then proceed to perform the necessary restoration work. Replacing the gasket will not lead to the desired result if the defect in the mating surface that led to its failure is left unrepaired.
8. The following subsections list the most common causes of ATF leaks and the conditions that must be met to prevent recurrence.
Note. Some of the above conditions cannot be met without the use of special equipment. In this case, the car should be driven to a service station.
Sealing surfaces
1. Periodically inspect the cover on the right side of the transmission case. Check that the fixing bolts are in place and securely tightened, make sure that there are no signs of mechanical damage on the cover.
2. Potential causes of cover leaks include overtightening of mounting bolts, damage to the transmission case sealing surface, gasket failure, and cracked or porous case walls. If the gasket of the cover or transmission case is formed by a sealant pad, the possibility of an incorrect choice of the type of the latter cannot be ruled out.
Seals and cuffs
1. The most typical causes of failure of transmission oil seals include an excessively high level of ATF, a violation of the patency of the ventilation breather, mechanical damage to the walls of the seat, damage to the oil seal itself, or improper installation of the latter. It is also possible that the trunnion of the shaft threaded into the stuffing box is damaged, or the latter has excessive play as a result of bearing wear.
2. Check the condition and correct fit of the dipstick guide tube seal. Periodically inspect the surface around the speedometer drive gear or speed sensor for signs of leaks (VSS). If necessary, replace the sealing ring.
Transmission housing
1. The reason for the development of ATF leaks may be the formation of cracks or pores in the body of the transmission case. Consult with car service specialists.
2. Check up tightness of union knots of connection of hoses of an ATF cooler.
Breather and filler neck
Breather or filler leaks can result from overfilling the transmission, coolant in the ATF, or a blocked breather or return port.