Checking oil pressure
1. Start the engine and warm it up to operating temperature (determine warming up by the coolant temperature gauge). Take the car for a full test drive. (In car repair shops, the oil temperature is checked by inserting a temperature sensor into the guide tube of the oil level indicator. The regulated temperature is 90°C).
2. Remove the upper part of the air filter.
3. Unscrew the plug and remove it together with the sealing ring.
Note: The plug on a 4-cylinder engine is located at the front on the right side of the cylinder block.
4. Screw in the oil pressure gauge instead of the plug, installing the sealing ring.
5. Check the oil level and top up if necessary.
6. Start the engine and leave it running at the appropriate idle speed for the crankshaft. The oil pressure must be at least 0.3 bar, otherwise check the oil circuit.
7. Stop the engine.
8. Unscrew the pressure gauge.
9. Screw in the plug with the sealing ring and tighten it to a torque of 40 Nm.
Supplement for 6-cylinder in-line engine:
1. The pressure measuring hole plug is located on the right side of the oil filter housing. The pressure values are given in Table 5.2.
Table 5.2. Oil pressure in the oil system of a 6-cylinder in-line engine
Screw in the plug, installing a new sealing ring, and tighten it to a torque of 15 Nm.
Supplement for 6-cylinder V-engine:
1. Remove the fan with viscous coupling.
2. Remove the fan shroud.
3. The pressure measurement hole plug is located under the oil filter housing. The pressure values are given in Table 5.3.
Table 5.3. Oil pressure in the oil system of a 6-cylinder in-line engine
Screw in the plug, installing a new sealing ring, and tighten it to a torque of 20 Nm.
Oil pressure warning light
The oil pressure warning light comes on primarily when there is a lack of oil. In this case, the engine components and parts receive little lubrication. This usually happens if the car takes a turn at high speed with a low oil level. In this case, the oil pump sucks in air instead of oil. The oil pressure drops sharply, which can lead to serious damage to the bearings.
Since the oil pressure is always normal at the required level, the E-Class models do not have an oil pressure indicator. The oil level indicator light is a signal that should always be paid attention to.
The oil pressure warning light came on
1. If the oil pressure warning light flashes at idle speed after driving fast on a highway or mountain road, this is a signal that the oil pressure has dropped due to too high a temperature and, as a result, too low oil viscosity. This is not dangerous if the light goes out when you press the accelerator pedal.
If the oil pressure warning light is constantly on
2. Stop immediately and turn off the engine.
3. Check the oil level and top up if necessary.
4. Check if the warning light comes on again. In any case, you need to find out the cause. Have the car towed to a service station. You can avoid serious engine damage.