We wrote not once already about it and we will write that oil is the blood of the engine. Analogous to the human body too high or too low pressure is very harmful for the drive unit. What could be causing this state of affairs?
The oil level is essential
No need to know the mechanics that the amount of oil in the engine, linked to its pressure. Too low a level will cause low oil pressure, while too high - excessive. However, not everyone knows about the two basic issues. To low oil level caused light oil indicator on the instrument panel, this oil must be really little. The structure of the lubrication system is provided for emergency operation with a low oil level, the oil and the strainer located relatively near the bottom of the oil sump. Often, a driver is informed in any way about level of oil below the minimum set by the manufacturer, although the most recent cars are often equipped with an electronic system for measuring the oil level, which guards it. So you can draw a simple conclusion - if it lights up the low pressure warning, situation is an emergency and requires urgent action.
The high level of oil is equally harmful and most commonly is the main cause of excessive pressure in the lubrication system. Then, the overflow valve of oil is not able to drain the excess back into the sump and reaches the unsealing of the engine, and even of bad work, for example timing system.
Unfortunately, without indicator showing oil pressure - a rarity in newer cars – we rather don't know about his excess. Rarely, however, there is a situation where the oil is too much. The main reason for this state of affairs in cars with a diesel engine equipped with a particulate filter is repeated, unsuccessful attempt to burn off the soot from the filter by giving more fuel to the combustion chamber. Excess fuel flows into the sump raising the level, but not the oil itself, because we have already deal with two different liquids.
The second cause of excessive oil is not valid checking its level. Often during changing the oil comes to a situation where mechanic is hurrying, wait for the oil to drain, check its level and complete "roughly". In some cases, removal of all the oil from the lubrication system is not always possible and the certain amount remains. Therefore, do not suggest the capacity of the system during filling, and often this occurs and the engine is up to 300 ml oil too much, although the reason is not always insufficient removal of the old oil. In some cars, the range between the minimum and maximumon bayonet is quite narrow and easily exceeded, so you should to pour more it carefully. Also, users checking the oil level on the sloping parking garages or backyards can add it by mistake too much.
The overflow valve or oil filter?
If the pressure in the lubrication system is incorrect, and the oil level is correct, the first suspicion falls usually on the failure of the lubrication system. Often a suspect becomes an oil filter. If the product is at least good quality,it is very rarely failure. Only after a long mileage on one oil filter can become full with dirt, but then the situation saves an internal valve that allows the flow of oil from bypassing the filter. This phenomenon is harmful to the engine itself, but more damaging would be a total lack of lubrication. Already same visual inspection of the filter may suggest another reason for failure. Often, with high pressure deformation can occur or covers the oil filter. Then the cause may be faulty overflow valve.
Overflow valve is a very simple device responsible for the correct pressure in the lubrication system. The oil pump generates significant pressure in relation to what needs engine for several reasons. Firstly during start the engine needs oil as soon as possible, hence the pump generates a higher pressure than is needed when the engine is running. The second issue is the increase in the speed at which the oil pressure should increase slightly. The overflow valve is set at the factory so that the bypass opens on pressure increase above 3 bars. The oil then goes back into the sump. However, sometimes there is a blockage the valve in open or closed position, which often cause is neglect of service.
Long don't changing, worn out engine oil can silt valve or wear off and lock it. If there is a blockage in the closed position, it will cause an increase in pressure in the system or momentary increases with increasing engine speed. However, the valve permanently open will result in drops in oil pressure.
Watch out for engine oil!
The principle when you are selecting oil is very simple - always use oil recommended by the manufacturer. The only exception to the rule is the use of oil permissible by the manufacturer, often with slightly different properties. Unfortunately, buying a used car can be uncertain as to the one of oil used by the previous owner. In practice, the workshop and among the users still circulates rule that if you do not know what oil to use, it must be chosen according to mileage and would rather not use a better - in engines with high mileage, you can use only mineral oil or semi-synthetic. It is also said that it is dangerous for an engine oil change for the better (from semi-synthetic to synthetic or from mineral to semi-synthetic) as this may cause leaks, resulting from the leaching of sludge "sealing". All this mythology should be dispel.
It's a fact that change an oil to fresh and in addition a lower body, better quality can rinse out deposits, but sooner than the leak, they cause pollution of oil channels or said overflow valve. Tear up pieces of deposits are quite dangerous for the engine, but first of all, they must exist, which is not a principle. They arise when we are using poor-quality oil and we rarely exchanged it. So if you use the car for a long time and regularly changing semi-synthetic oil, basically changing on synthetic will not be harmful. However for the safety of this an exchange must be preceded by rinsing the lubrication system, which usually conflicts with the principle of washing the "sealing" of deposits. You should also rinse the system after buying the car if you do not know what oil was used by predecessor.
It is worth to know that in older cars manufacturer recommended determined the body of the oil not only structural reasons but because the market. Because not everywhere because synthetic oil was easy available and inexpensive, and therefore if to the same model of car and engine in another country and newest model is recommended synthetic oil, you should go from semisynthetic to synthetic, although this is not necessary. You should also remember not to change the oil extreme, i.e. mineral to synthetic and synthetic to mineral, unless in the engine is the wrong oil.
Other causes of abnormal oil pressure
Once the most common causes of abnormal oil pressure are still otherswhich occur rarely. In heavily exploited engines clearances on setting of the crankshaft causing pressure drops. If, however, after the repair these clearances are too low, it can reach up to increase of the oil pressure. Another cause too high pressure are pollutioned oil passages. However a low pressure is caused by the oil pump failures (excessive clearances), a too low body oil (wrong choice, contamination by fuel or overheating) and pollution of the oil filter on a strainer. Banal, but also encountered cause lighting oil control is failure of pressure sensor.