Failure of hydraulic control valve body of the hot

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Auto transmission hydraulic control valve failure

the electronic control system, hydraulic system and mechanical force application device in the automatic transmission are closely related to each other. The hydraulic system, in particular, uses oil circuit to control the valve body, which is very precise. It has labyrinth like oil passages like a printed circuit board, plungers of different sizes, springs of different lengths and thicknesses, steel balls, plastic balls, filter seat rings, limit plates, accumulators and other titles. The direction, location and size of parts are confused. To repair the valve body, you must have detailed information, fully understand and examine it before you start. For the at wave box, only when the friction plate is seriously burned, the planetary gear unit is worn, the vehicle mileage is 1/4, and the ATF oil is seriously dirty, the valve body will be disassembled. The performance of the cleaning machine is very rare in the market

in the electronic hydraulic automatic transmission, the failure of the oil circuit control valve body is mostly caused by the internal dirt and blockage of the oil circuit. Disassembling and cleaning the valve body is an indispensable part of overhauling the automatic transmission. The oil suction height of the hydraulic pump of the pressure testing machine is generally not more than 500 mm

① before removing the valve body from the bottom of the gearbox, take extra care when removing the flat wire of the external solenoid valve. As the solenoid valve connector on one side of the flat line is a plastic product, it has been immersed in ATF oil for a long time in the past two years and is very fragile under high temperature. Use a self-made special tool to fully insert it under the solenoid valve plug, pull out the plug and harness in this direction, properly place it, remove the parts that are easy to fall off the surface, remember the original position, put the valve body into kerosene for a long time, and then take out the empty part to understand the net

② place the valve body on a clean workbench, remove the connecting screws between the upper and lower valve bodies, hold the upper part of the valve body and the middle diaphragm firmly together, and turn over together to make the middle diaphragm upward (this can prevent the one-way steel ball from falling), and then pick up the diaphragm for the next operation. After the diaphragm is removed and before the plunger of the control valve body is removed, use the residual oil on the oil circuit diaphragm, copy the oil circuit diaphragm drawing with a slightly thick white cardboard, and mark all parts in the oil circuit diaphragm one by one on the drawing for future reference during reassembly

③ put the valve body into clean kerosene and clean it with carburetor cleaner. Use a small brush to clean the oil dirt deposited in the oil duct. If necessary, wipe it with nylon cloth. Visually check that there is no crack and deformation on the valve body. Each plunger should operate flexibly when pulled with a small screwdriver, and the piston surface should be free of cracks. Place the empty valve body flat on the table, and inject a little automatic transmission oil into each oil hole and oil duct, At the same time, remove all small parts from the diaphragm, clean one of them, dry them and install them into the valve body. At the same time, check that all parts should be complete and in good condition

④ check whether the plunger is stuck. In the control valve body, except that the plunger of the manual control valve has no limit device that can be taken out directly, the outer ends of all other plungers have limit devices, which include cylinder, card and bayonet pin. The cylindrical limit device only needs to gently push the plunger inward, and the limit pin can fall off. The card or cotter pin needs to be disassembled with tools. During the disassembly process, fingers or screwdrivers are needed to hold the plunger, so as to prevent the plunger from popping out under the action of the inner spring at the moment of the removal of the limit device

if the plunger is stuck in the valve hole and cannot fall out freely, it can be taken out by gently tapping the valve body with a wooden hammer or rubber hammer. The stuck plunger can be polished along the arc direction with 1200 * sandpaper stained with ATF oil. Only the plunger can be polished, and it can also be polished with toothpaste. The valve hole cannot be polished, and it can be polished to the standing valve body. On the premise of being clean, the plunger can slowly slide to the other side only by its own weight. In the process of disassembling the plunger, it is best to overhaul one group and disassemble the other group after reassembly, so as to avoid the wrong position between each other

check the free length and diameter of the spring, and check whether the free length and diameter of all springs in the valve body meet the standard by referring to the information in the maintenance manual one by one. The new spring also needs to be checked in this regard. The missing installation of the one-way ball valve will cause serious shift impact on the relevant gears. At the same time, the wrong installation of the damper block of the throttle valve will also cause shift impact on the middle of the valve body, which looks like a card. Be sure to pay attention to the front, rear, left and right adjacent positions of all components. Any small mistake will cause the valve body to fail to work normally

⑤ replace the sealing ring on the control valve body, and whether the working oil circuit of the force application device is sealed mainly depends on the following aspects: 1 The sealing ring on the working piston of the force application device; 2. Piston sealing ring on accumulator; 3. Sealing ring on control valve; 4. The sealing condition of the sealing rings on both sides of the oil inlet of the clutch support. During the overhaul, the sealing rings in these four aspects must be completely replaced. Whether the accumulator piston has cracks and whether the piston ring is worn must be carefully checked. Otherwise, the automatic transmission is very easy to burn the friction plate after the overhaul, and the force application device will be ablated again after driving for about 3000km, which is directly related to the above four aspects

⑥ clean and dry the clapboard, and check that the clapboard should not have large deformation. Carefully observe that each oil hole should be smooth and light tight (place the one-way ball valve in the corresponding hole of the clapboard) and shine with light, and check whether there is light leakage on the reverse side. Note that the old and new sealing gaskets and diaphragms of the valve body must be close together, and check whether the hole diameter and oil direction on the paper gasket are consistent with those on the valve body (this is very important). At the same time, soak the sealing gasket to be installed with ATF oil for a few minutes, and then according to the disassembly steps, put the valve body flat and push the components one by one, rather than erect the valve body vertically. Then buckle the upper and lower valve bodies and the middle diaphragm together, and tighten the connecting screws evenly and crosswise (pay attention to the length of the screws, and do not install them in the wrong position). The tightening torque is generally between N M. For example, the tightening torque of Volkswagen transmission control valve body bolts is 5N m, which cannot be too large or too small. The torque directly affects the oil pressure. So far, the valve body is assembled

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