Maintenance Useful tips

Engine Oil is Leaking! What Are the Common Causes and What Can Be Done About It?

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If you want to take care of your car, "Engine Oil Leakage" that is worrisome. If you have a high mileage car, it is a sign that the oil leakage cannot be avoided.

In this article, we will explain to you what are the causes and the symptoms of oil leakage, and whether you can deal it yourself or not.

What Are the Symptoms of Engine Oil Leakage?

As engine oil continues to leak, it will cause great damage to the engine. So it is important to realize it quick if the engine oil is leaking or not.

In order to do so, we need to know the symptoms and other information regarding it.

Is It Really the Engine Oil?

Oil is used in every part of the car for various purposes, including the engine oil.

  • For automatic cars, there is a transmission fluid called ATF oil.
  • Brakes are now operating with hydraulic pressure so brake oil is also used for brakes as well.
  • Also, since most of the steering wheel is power steering, power steering oil is also in use.

In order to see where the engine oil leakage is coming from, you have to know the common spots where the oil is leaking out from the car. If the oil leakages from the engine drips directly from the engine, there is no doubt that it is the engine oil.

However, depending on the leakage, oil may drip out from the engine and transfer to other parts of the car. If you follow the oil trail, you will find out where the oil came from.

Another way is to check it by how the car operates. If the effectiveness of the brake gets weaker or when the brake feeling feels different from usual, you have to check the brake oil.

For ATF oil, if the transmission is not smooth enough, there is a chance your ATF oil leaked out. And also check the power steering oil, you will feel heavier handle while driving if the oil is not enough.

In addition, there is one common easy mistake that everyone does and it is to mistake engine oil to cooling water.

Most of the current cars are water-cooled engines, the water is chilled inside the radiator and it is used to cool the inner part of the engine.

Since the radiator is mounted on the front side of the engine, cooling water could leak out from the radiator and it may be mistaken for engine oil.

It is easy to differentiate between these two. When you touch it and feels sticky, it is the engine oil, while cooling water is just simply water.

Specific Symptoms of Engine Oil Leakage

The engine is assembled by joining multiple metal parts with bolts and nuts and there is always a gap between those parts.

If it is a new car, the joints are clean. But, as you use the car more often, the joints will get dirty. The reason it got dirty is not because the car is getting older, but because the engine oil oozed out from the joints and got mixed up with dust and other impurities.

To check, open the bonnet and you can easily see the dirty joints on top of the engine.

Why Does Engine Oil Leak?

As we mentioned before, car engine have gaps between the metal parts. So if it is a new engine and you leave the gaps the way it is, the engine oil will leak right away.
So in order to cover these gaps up, rubber packing are sandwiched into the joints.

As the car engine gets hot when you drive the car and the car is parked outdoor for so long, these rubber packing will start to deteriorate and turn hard. Then, the gaps will slowly reform and the engine oil will start to leak again.

Cause of Engine Oil Leakage

Most leakages are caused by the deterioration of the rubber packing mentioned previously.
This occurs commonly regardless of the type of engine. However, there are other reasons for engine oil leakage.

・The Viscosity of the Engine Oil Is Low
It is easier for oil to leak out even from a little gap if the oil has low viscosity.

・Loose Drain Bolt
Drain bolt is usually used when replacing the engine oil. It is located at the bottom of the engine.

So when you replace the engine oil, and the bolt is not tightly fastened, the leakage occurs as the bolts loosen up due to vibrations.

Types of Engine Oil Leakage

Oil leakage from the engine may leak not only to the outside of the engine, but also inside the engine.

External Engine

・Oil leakage caused by deterioration of rubber packing placed in between the joints of head cover, oil pan, plug hole, etc.
・Oil leakage due to the loosed out bolts at various parts of the engine, including drain bolts

Inside the Engine

・Oil leakage due to worn out piston ring that is used for filling the gap between the engine’s piston and cylinder, and this allows oil to drip from the bottom of the piston down to the combustion chamber.
・Oil leakage from gaps caused by deterioration of the valve that circulates gases for the combustion chamber, and the stem seal that fills the gap between the engines.

Oil Rising, Oil Falling
The oil leak inside the engine is also called "Oil rising, Oil falling".
・Oil rising is a state in which the gap between the piston ring and the cylinder becomes large due to the distorted piston ring, and thus making it useless.
・Oil falling is a state in which the stem seal attached to the valve is hardened due to deterioration, and so gaps are formed , making it useless.

Trouble Caused by Oil Leak outside the Engine

Trouble Caused by Oil Leak Outside the Engine

The tire passes over the leaked oil, causing a slip.
If you run with leaking oil from the engine, the oil may get on to the tires of your car or other people’s car during cornering. And if it does get on to the tire, the car could slip and become uncontrollable, leading to serious accidents and it is very dangerous.

The leaked oil will catch fire resulting in a vehicle fire.
There is no guarantee that the oil will not catch fire. If it gets ignited, it will be a serious accident involving life.

Troubles of Oil Leak inside the Engine

The muffler gives off smoke of burned odor due to the oil dripping into the combustion chamber, the oil will burn and white smoke of odor will come out of the muffler.

Common Problem

The car will not run as smooth if the oil is not enough for the parts that need it.

Regardless of which oil that leaks, if you leave it as it is, the amount of oil will keep on decreasing and will eventually run out.

The Risks When Oil Lamp (oil pressure warning light) is On

When hydraulic pressure drops, the oil lamp will light up, and it means that the engine oil had decreased from a specified amount.

The engine is in a dangerous state when the oil lamp lights up.

Engine oil provides lubrication and cooling for the engine. So, if you leave the oil leakage until this oil lamp lights up, the friction of the engine will increase and it will start to heat up, in the worst case this could lead to engine breakdown. You can no longer use the engine once it broke down.

Actions You Can Do, First Aid Measures

If you know that the engine oil is leaking, it is best to ask the professional dealer or repair shop to repair the oil leak.

However, if you cannot request the repair immediately, or if it is not too bad of a leakage, you can try doing it yourself by giving first aid measures to your car.

Putting Additives

Every oil manufacturer has its own additives sold separately from the oil itself.

Additives have features such as improving the performance of oil, improving its start ability, improving fuel economy, power up, etc. Some of them have the effect of reducing oil leakage.

Although the merit would be its immediate effect, the disadvantage is that it does not last long. So it is the best option for a first aid measure.

Increasing Viscosity of the Oil

The viscosity of oil means the stickiness of the oil. If the oil is smooth like water it will leak even from a small gap, but if it is viscous, it will not leak easily.

Increasing the viscosity of oil creates a condition where oil is less likely to escape from the gap.

Do a Repair on the Rubber Packing Which Deteriorated and Became Hard

New rubber packing is soft and it fills the gap by crushing it moderately. As it is exposed to high temperatures, the rubber packing deteriorates over time, gets stiff, creates gaps, and results leakage from there.

By repairing the deteriorated rubber packing, it will fill the gap and prevent the oil leakage again.

Using a Leak-Proof Agent

It is similar to additives as it is mixed into the engine oil, so it is better to put it in at the same time as engine oil replacement.

The leak-proof agent stops the oil leak by softening the rubber packing that became hard due to deterioration.

The advantage is that it is cheap and the effect lasts to a certain extent. But, the disadvantage is that it does not have an immediate effect compared to additives, and it is necessary to travel to some extent before the effect comes out.

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