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5.1.5. Hydropushers

The hydraulic system of adjustment of valves serves in order that in valves there was a gap and the closed valves densely adjoined to a saddle. Hydropushers are located between cams of the camshaft and an end face of a rod of the valve. Difference of system with hydraulic adjustment — the course of valves without gaps significantly reducing noise in comparison with operation of ordinary valves.

Knock of valves at launch of the engine
When the engine long time did not work, the knock of valves is not the reason of breakage. At long not working engine oil from hydropushers flows down. When the engine is launched, hydropushers are filled with oil at once, and the knock vanishes.
If the knock of valves in the field of a head of cylinders continues on the heated-up engine, it testifies to defects of one or several hydropushers. They are not subject to repair therefore they should be replaced.
The reasons of knock of valves can be the following:
1. Before launch of the engine in it oil was replaced.
2. The engine did not work more than a day.
3. The engine is launched after replacement of pushers.

   Principle of hydraulic adjustment of thermal gaps of valves

Fig. 4.18. A hydropusher in a section: 1 – camshaft; 2 – the oil tank in the case; 3 – backpressure valve; 4 – channel of supply of oil; 5 – zone of high pressure; 6 – valve rod; 7 – spring; 8 – cylinder; 9 – piston; 10 – hydropusher case

Hydropushers consist of two main details — the piston and the cylinder (fig. 4.18). The spring presses the piston to a pusher surface. At the closed valve oil passes from the engine lubrication system on oil gallery in a block head through a perepuskny opening in the pusher case in the pusher cylinder. The backpressure valve of a pusher is open, and oil fills piston grooves. When pressing a cam of the camshaft a pusher the case presses it on the piston under the influence of which the valve is closed and stops oil restart-up. As liquid does not compress, oil in this case serves as rigid connection between a cam of the camshaft and a rod of the valve therefore when pressing the valve the gap is absent. The difference of pressure at the same time is compensated by restart-up of oil from the pusher cylinder in its case, carrying out additional lubricant of working parts of cams of the camshaft. After closing of the valve pressure in the case of a pusher falls, the backpressure valve opens, and the cylinder is again filled with oil.
At long operation of the engine of a detail of the valvate mechanism wear out, however thanks to the principle of work of hydropushers an inspection of gaps of valves can be carried out through rather wide interval of time.

   Check of hydropushers
1. Warm up the engine.
2. Leave the engine to idle before the first turning on of the fan.
3. Let's work to the engine within 2 min. on the raised turns (2500 min.-1).
4. Switch off the engine.
5. Uncover a head of cylinders.
6. Turn the engine that that time until at the checked cylinder cams of the camshaft are directed up.

Fig. 4.19. Check of a hydropusher: 1 – pusher; 2 – wedge

7. A wooden or plastic pin press on a pusher (fig. 4.19).
8. If at the same time the pusher quickly and without resistance falls, it should be replaced. Experts in auto repair shop have to do this work.

Work on the raised turns
Work on the raised turns reduces engine service life. If the engine works at the raised turns and at the same time knocks or noise are heard, it speaks about wear of a bent shaft or the valvate mechanism. If wear strong, then breakage of a pusher is possible. As a rule, it leads to serious breakage of the engine
Some malfunctions of hydropushers, their reasons and ways of elimination are given in the table.