5.13.2. Check and replacement of hydropushers

The hydropushers of the VAZ-21126 engine executed in the form of the cylindrical pushers located between the camshaft and valves combine two functions: transfers of effort from the camshaft to valves and elimination of gaps in their drive.

Fig. 5.8. The scheme of work of a hydropusher in the valvate mechanism of the VAZ-21126 engine: 1 – valve; 2 – spring of the backpressure valve; 3 – backpressure valve; 4 – head of the block of cylinders; 5 – camshaft cam; 6 – pusher; 7 – plunger; 8 – plunger spring; 9 – sleeve; 10 – case of the backpressure valve; And, B – hydropusher cavities; In – the oil channel

Work of a hydropusher is based on the principle of incompressibility of the engine oil which is constantly filling an internal cavity of a hydropusher during the operation of the engine and moving its plunger at emergence of a gap in the valve drive. Thus the continuous contact of a pusher with a camshaft cam without gap is provided. Thanks to it need of adjustment of valves at maintenance disappears. The principle of action of a hydropusher is shown in fig. 5.8. Oil under pressure necessary for work of a hydropusher, moves in internal cavities And yes B from the channel In engine lubrication systems through the side opening in a pusher 6 executed in a ring pro-point of its cylindrical surface. At the closed valve 1 pusher 6 (through a plunger 7) and a sleeve 8 are pressed by the 9th holding apart effort of a spring respectively to a cam of the 5th camshaft and an end face of a core of the valve. Pressure in cavities And yes B is identical, the backpressure valve 3 hydropushers is pressed to a saddle in a plunger by the 7th spring 2 – gaps in the valvate mechanism are absent. At rotation of the camshaft the cam 5 runs on a pusher 6, moving it and the related plunger 7. Movement of a plunger 7 in a sleeve 9 leads to sharp increase in pressure in a cavity B. Despite small leak of oil through a gap between a plunger and a sleeve, a pusher 6 and a sleeve 9 move for a single whole and open the valve 1. At further rotation of the camshaft the cam 5 reduces pressure upon a pusher 6 and pressure of oil in a cavity of B becomes below, than in a cavity And. The backpressure valve 3 opens and passes oil from a cavity And, connected to the oil highway of the engine, in B. Davleniye's cavity increases in a cavity of B, a sleeve 9 and a plunger 7, moving relatively each other, choose a gap in the valvate mechanism.
Pressure of the oil brought to hydropushers is regulated by the valve installed in a head of the block of cylinders. As after an engine stop from the channels going from the oil pump, oil flows down in an oil case, and channels of a supply of oil to hydropushers remain filled, after launch of the engine in cavities of the last air traffic jams can be formed. For their elimination the calibration compensation openings providing an automatic purge of cavities of hydropushers are provided in channels of supply of oil of the engine. Besides compensation openings allow to reduce several pressure of the oil coming to hydropushers with a big frequency of rotation of a bent shaft of the engine when pressure in a cavity of a hydropusher can become so big that its pusher, having leaned on an occipital part of a cam of the camshaft, will slightly open the valve at the moment which is not corresponding to a gas distribution phase.
Practically all malfunctions of hydropushers diagnose on the characteristic noise published by the gas-distributing mechanism in various power setting.
Noise from valves sometimes manages to be eliminated with small turn of a spring or the valve around a longitudinal axis. For this purpose execute the following.
1. Turn a bent shaft in situation at which the valve publishing noise will begin to be slightly opened.
2. Turn a spring a little — also the valve at the same time will turn.
3. Launch the engine. If noise does not disappear, repeat operations 1 and 2.
4. If the turn of a spring and the valve does not yield desirable result, check a condition of a spring and measure gaps between cores of valves and the directing plugs (see. "Dismantling, repair and assembly of a head of the block of cylinders"). Eliminate increased (in comparison with nominal) gaps.
If the valve and a spring are serviceable, and the knock of valves is all the same listened during the operation of the engine, the hydropusher is faulty. Replace it as follows.

Perform work in 20–30 min. after an engine stop.

1. Uncover a head of the block of cylinders (see. "Replacement of laying of a cover of a head of the block of cylinders").
2. Remove camshafts (see. "Replacement of oil scraper caps").
3. For check of a hydropusher press it. If the hydropusher is serviceable, it has to utaplivatsya with considerable effort if this effort is small, the hydropusher is faulty. It is also necessary to check ease of rotation of a hydropusher in a block head nest. If the hydropusher does not rotate or rotates with big effort, it needs to be replaced.
4. Take a hydropusher from a nest of a head of the block of cylinders.

To take a hydropusher the magnet which is conveniently suitable by the sizes.

5. Grease a new hydropusher and a nest in a head of the block of cylinders with engine oil and establish a hydropusher in a nest.
6. Other hydropushers replace similarly.
7. Install the camshaft and details of the drive of the gas-distributing mechanism as it should be, the return to removal.

After replacement of a hydropusher the engine at the first start-up can work short time with the increased noise until hydropushers are pumped over. For acceleration of pumping of hydropushers let's the engine work with the increased rotation frequency within 1–2 min.