On this section of a diesel engine, you can clearly understand the relationship between the crankshaft and the valve control mechanism:
1 - valve
2 - valve spring
3 - pusher
4 - camshaft
5 - piston
Oil pump (removed from engine) consists of two gears meshed with each other (1 and 3). The engine oil is sucked in through chamber 4, and the pressurized oil flows through chamber 2 to the engine lubrication points.
The oil flows back into the oil sump through the holes and can be sucked in by the oil pump for a new lubrication cycle.
Safety valve
If the oil filter element is dirty due to its untimely replacement, then the safety valve comes into action. It opens and the filter is bypassed by oil flow, allowing oil to enter the lubrication system. In this case, however, unfiltered engine oil increases engine wear.
Oil pump
About 35 liters of oil per minute is pumped at full throttle through the engine. The oil pump is driven by the intermediate shaft already mentioned. On the Golf/Vento models we used a conventional gear pump. Two meshed gears pump oil from the suction chamber to the pressure chamber.
Pressure reducing valve
In order to prevent the oil pressure in the lubrication system from becoming too high, there is a pressure reducing valve on the oil path from the oil pump to the oil filter, which, if necessary, opens and excess oil flows back to the suction pipe.
Oil radiator
The Volkswagen Golf/Vento and diesel are equipped with a through oil cooler which is integrated between the oil filter and the oil filter holder. The oil in the radiator is constantly cooled by the pumped coolant or, when the engine is cold, it is slightly heated by the already heated coolant.
Oil temperature
For optimal engine performance, oil temperature plays a decisive role. Due to the lack of an oil temperature gauge, it is impossible to track how the engine's thermal balance is maintained. More dangerous than high values are low oil temperatures. At temperatures below 60°C, oil additives are not yet fully effective, which leads to significant engine wear. Therefore, if possible, do not increase the engine speed after a cold start above 3500 rpm. until the oil reaches a temperature of approximately 60°C. As a basis, it can be assumed that engine oil reaches 60°C in winter in about 10 minutes, in the warm season - already after 6 minutes.
Oil pressure
At an oil temperature of 80°C, the pressure at 2000 rpm must be at least 2 bar. In this form, it is impossible to control. As a standard control option, there is a control switch that extinguishes the signal light on the instrument panel at pressures above 0.15-0.45 bar, as well as a second switch. which signals too low pressure at high engine speeds. If the pressure drops below 0.9 bar at engine speeds above 2150 rpm, the warning lamp flashes and an audible signal sounds. For more information on oil pressure control, see the section «Tools and devices».
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