At idle the oil pressure light comes on
i would say the car is safe to drive.IF the pressure sensor was
working correctly, and your engine was a complete dog, then you would
expect there to be some loss of oil pressure, but not 0 to 4bar in a
blip of the throttle.given that the oil pressure sensor is a
common fault (and it controlls the oil pressure light, it is not a
seperate switch), i would say the sensor has a 'dead' spot on it, and a
blip of the throttle just sees it outside the dead zone of its reading,
and pings back to 4bar (its natural to get a slight rise in oil pressure
when higher revs are acheived). 4bar is the right value, its what mine
sits at. maybe a tiny bit under (3.95) when the engine is very hot/in
traffic the
oil pressure is reading just over 4 at all times, dosent go up or when
accelerate or down at idle is this normal, used to mercedes W124 where
it can register .3 up on idle but when accelerate it should goto max, ie
3 bar Whats the mileage on the car. Sounds like It certainly is suffering from low oil pressure at tickover, but loads of cars do and continue running for thousands of miles. blue/white smoke on start up and that points to valve seals and, yes, the head would have to come off to replace them, but it's normally just blue smoke. White smoke points more to head gasket, but that would be replaced anyway when doing the valves.Bet the engine sounds smooth as silk too
Oil
pressure is determined by the rate at which oil flows through the
internal combustion engine of a car. Low oil pressure is a real danger
for engines, as it indicates that the bearings in an engine have worn,
allowing the oil to flow more easily and at a lower pressure. However,
high oil pressure is generally not a concern for motorists. Oil pressure
fluctuates with the heat of a machine, and though high oil pressure can
indicate a serious problem, it generally means the engine is in an
adjustment period.Oil Pressure at Idle For many cars, oil pressure is
much higher upon start-up or while idling. The reason for this has to do
with the temperature of the engine. When an engine has been sitting
turned off, it cools down, as does the oil that flows through the
machine. Upon start-up, the engine temperature begins to rise. As it
rises, so to must the oil heat up to find a level pressure to flow
through the machine. Cooled oil is thicker, causing it to flow more
slowly and at a higher pressure through the machine, until it reaches
its optimal operating temperature.Pressure Relief Valve Recurrent high oil pressure,
even after the machine has been running for a while, can indicate a
problem with the pressure relief valve. The pressure relief valve is
responsible for regulating oil pressure throughout the internal
combustion engine. It is a safety device intended to keep vessels or
piping from experiencing extreme pressure. When this device is
malfunctioning, it will cause high oil pressure in an automobile.Types of Oil The type of oil put into an
engine can also account for extremes in oil pressure. Low-weight or thin
oils will operate with low oil pressure, as they will pass through the
machine quite easily. Thicker oil will pass through the machine at
higher oil pressure readings. Generally, after an oil change, when fresh
oil is introduced into the machine, oil pressure will increase. This,
however, is only a sign that the oil that formerly operated your car was
too thin for optimal performance.
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