Why is the Oil Light Comes On and Off but the Oil is Full | Car Troubleshooting

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Why is the Oil Light Comes On and Off but the Oil is Full

Oil warning light

Car troubleshooting

Whenever oil warning lights flicker, the obvious question is, is there enough oil in the engine? So, check first the level of the engine oil.

Remove the oil dipstick and check its reading.  If you haven't done this before, please review the procedure as described in this car's owner's manual.

If the engine oil level is low, this is causing the oil warning light to flicker. This is most likely what is responsible for the occasional flickering of the oil warning light.  More specifically, a low oil level will cause the oil pressure inside the engine to temporarily drop. When this happens, the warning light will flicker.

What to do?
Add some oil to the engine. Do not add too much! Refer to this car's owner's manual if you aren't sure as to the proper amount or type of oil this car engine requires.

If the engine oil level is not low, then the problem is not low-level engine oil. Now observe if the oil warning light flickers only when the engine is hot.

Oil light comes on and off but oil is full

If the engine oil flickers only when the engine is hot, the problem could be a wrong viscosity oil or degraded old oil is causing the oil light to flickers occasionally while driving.

As indicated, the oil warning light flickers ONLY when the engine is hot.  Therefore, the following is most likely what's going on here. The hot engine is causing the oil to become thin which, in turn, is causing a reduction in oil pressure. As a result, the oil warning light comes on.

Now, at this point, you may be saying, "But shouldn't the oil be able to withstand high temperatures and not become so thin that the oil pressure drops?"  The answer is "yes" unless the oil is of the wrong viscosity or has degraded. Viscosity refers to the thickness of the oil. The higher the viscosity rating, the more resistant the oil will be too high engine operating temperatures (i.e. the more resistant it'll be to become thin). Also, oil degrades with ti(mainly caused by dirt which gets past the air cleaner and into the oil).  Degraded oil has a tendency to thicken quickly under high engine operating temperatures.

What to do?
Get an oil change. Make sure the right type of oil is put into the engine. Refer to this car owner's manual for this information. If the oil warning light flickers even when the engine is not hot, then the problem is not about the viscosity of the oil. Now observe if the oil warning light flickers only when the engine idling.

How Often Should You Change Your Oil

For the normal operation conditions, the oil change is every 6 months or every distance of 5,000 km whichever comes first for diesel engines.

Learn more: How Often Should You Change Your Oil in Months

If the oil warning lights flicker only when the engine idling, then the problem is a failing oil pump or partly clogged oil pan screen.

Oil pan

First, let's get some background info, an oil pump does the following - it draws engine oil from the oil pan through a screen (to filter out sediment), and then spews the oil up to the engine (to lubricate it).  The faster the engine runs, the faster the pump operates. The oil light flickers ONLY at engine idle. This means the oil pressure isn't adequate at idle. From the above diagnosis, the only thing that can be said in regards to the "Failing Oil Pump" theory (without going into too much detail) is that the design of most oil pumps is such that any flaw in the pump will tend to reveal itself at a slow operating speed (e.g. at engine idle and not really at a higher speed (e.g. when the engine isn't at idle).

Also, a partly clogged oil pan screen inhibits the efficiency of the oil pump, causing a drop in oil pressure and thus a flickering of the oil warning light. This occurs mostly when the pump is operating slowly (i.e. at engine idle).

What to do?
Do the simplest/cheapest thing first which is getting an oil change. In addition to draining/replacing the oil, make sure the mechanic cleans the oil pan and screen.  If you're lucky you won't see the oil light flicker anymore. However, if it still does, all is not lost... you can never have the oil changed too frequently.  Also, you'll know that the problem most likely lies with the oil pump. Therefore, have a mechanic inspect it.

If the oil warning light flickers not only when engine idling, the problem could be a failing oil pump or a bad oil pressure sensor or wiring.

Bad oil pump

The oil warning light's flicker isn't limited to when the engine is hot.  Further, it's not limited to when the engine is idling either.  From this, it would seem that the oil light probably comes on (i.e. flickers) at random. One explanation of this is that the oil pump is occasionally failing (i.e. in a random fashion).  More specifically, each time the pump fails for a second, the oil pressure inside the engine drops and consequently the oil warning light flickers.

Another possible explanation is that the oil pressure sensor is bad and therefore it is incorrectly reading the oil pressure. In other words, at times it "thinks" the oil pressure is low even though it’s not.  Therefore, it sends some current to the oil light which causes it to flicker. Also, the wiring of the oil pressure sensor may be bad/loose. This would cause the oil light to flicker each time the loose wiring shorts out.

What to do?
Take the car to a qualified mechanic and ask him to inspect both the oil pump and the oil pressure sensor and its wiring.  Make sure you explain to the mechanic exactly what this article explained to you. Please have this problem taken care of soon.  If it is indeed true that the oil pump is failing, you'll do damage to the engine if the pump fails completely one day as your zipping down on the highway.

On the other hand, if the mechanic tells you the problem is a bad sensor/wiring, don't skip having the repairs done.  The oil warning light is there for a reason and, you'll want to have confidence that if it does go on in the future, it actually is warning you.

Warning Lights on the Dashboard

What is that warning lights on the dashboard mean? If these dashboard warning lights are lit it means something is wrong with the car to warn the driver.

Learn more: Warning Lights on the Dashboard

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