Oil leaks are no laughing matter. Unfortunately, while they should be easy to repair, you may find yourself finding leak after leak within your car. You definitely don’t want those leaks sticking around for a long while, because that will negatively impact your car’s overall performance. As such, knowing about oil leaks, including where those leaks come from, is key in diagnosing the issue. Today, you are going to learn the most common reason your car is leaking oil—worn oil seals—including why it happens so frequently. Let’s get started.

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What Causes Oil Leaks?

If you are wondering why oil is leaking from your vehicle when it is parked or just after doing an oil change, you are going to have to do some detective work. It can be difficult to quickly diagnose an oil leak in your vehicle since there are many possible causes.

Here are some common causes of oil leaks in vehicles:

  • Loose or Damaged Oil Drain Plug: The oil drain plug is responsible for sealing the oil pan and preventing leaks. Make sure the drain plug is tightened properly and not damaged when you do an oil change. Any cracks or issues with the drain plug can cause leaks.
  • Worn Gaskets or Seals: Over time, the gaskets and seals in the engine can deteriorate or become worn, leading to oil leaks. This can include gaskets and seals such as the valve cover gasket, oil pan gasket, camshaft seals, crankshaft seals, or the oil filter seal. When these components degrade, they can allow oil to seep out.
  • Cracked or Damaged Engine Components: Any cracked or damaged engine components, such as the oil pan, engine block, or cylinder head, can cause oil leaks. This can occur due to impact from road debris, improper installation, or other factors.
  • Faulty Oil Filter: A defective or improperly installed oil filter can lead to oil leaks. If the oil filter seal is not properly seated or if the filter itself is damaged, it can result in oil leakage.
  • Engine Gasket Failure: The engine consists of various gaskets that seal different engine components. If these gaskets fail, such as the head gasket, timing cover gasket, or oil pan gasket, it can result in oil leaks.
  • Overfilled Oil: Overfilling the engine with oil beyond the recommended level can cause excess pressure, leading to leaks.

Signs of Car Leaking Oil

How can you tell if your car has a problem? Aside from spotting oil puddles or stains underneath your vehicle, there are some other signs to keep an eye out for. Keep in mind that these signs can also help you diagnose where the leak is coming from.

Signs of oil leaking from your vehicle:

  • Excessive Exhaust Smoke: DO you see any white or bluish smoke coming from the exhaust? This is an indication that oil is leaking into the combustion chamber and being burned instead of lubricating your engine.
  • Engine Overheating: If there is an oil leak, the engine may not receive sufficient lubrication, leading to increased friction and heat buildup. This can result in engine overheating, which is typically indicated by a rising temperature gauge on the dashboard or the appearance of a warning light.
  • Burning Smell: The oil heats up and emits a distinct odor as it comes into contact with hot surfaces. This smell is often described as a burning or oily scent.
  • Constantly Low Oil Level: Do you have to top up your oil again? Something is wrong. If you consistently notice a low oil level between oil changes or if you need to frequently add oil, it could be a sign of an oil leak.
  • Poor Engine Performance: An oil leak can negatively affect the performance of the engine. You may notice a decrease in power, rough idling, or a loss of acceleration. This can occur if critical engine components are not receiving sufficient lubrication due to the oil leak.

What is the Most Common Reason a Car is Leaking Oil

Now, which reason for oil leaks is most frequent? That would be worn or faulty oil seals. Oil seals are designed to create a tight seal between moving engine components, such as the crankshaft or camshaft, or the valve cover gasket, and the stationary parts, like the engine block or cylinder head. Over time, these seals can become worn, brittle, or damaged, leading to oil leaks.

Why do these seals become faulty or damaged? Here are some reasons:

Mileage and Age

As a vehicle ages and accrues mileage, the oil seals are exposed to constant heat, pressure, and the friction of moving parts. This continuous wear and tear can cause the seals to degrade and eventually fail. The constant cycling between hot and cold temperatures can also contribute to seal deterioration.

Poor Maintenance

Regular maintenance, including timely oil changes, is crucial for preserving the integrity of oil seals. Clean engine oil provides lubrication and helps to keep the seals in good condition. If oil changes are neglected or performed irregularly, dirty or contaminated oil can accumulate and accelerate seal wear. Low-quality or improper oil can also contribute to seal degradation and increase the likelihood of leaks.

Extreme Temperatures

During operation, the engine generates high levels of heat. Since the oil seals are closely located to the engine and are also subjected to high operating temperatures. The oil seals are crafted out of rubber, a material that hardens, cracks, and shrinks when exposed to extreme temperatures. This deterioration compromises their ability to maintain a tight seal, resulting in oil leakage.

Improper Installation

During engine repairs or maintenance, if the oil seals are not properly installed or seated, it can result in leaks. Correct installation techniques, such as ensuring the seals are positioned correctly and using appropriate tools, are vital for maintaining their effectiveness. Using substandard or incompatible seals can also compromise their performance and lead to oil leakage.

Harsh Driving Conditions

Driving in extreme conditions can put additional stress on the engine and its components, including the oil seals. High temperatures, such as those experienced in hot climates, can accelerate seal deterioration. Dusty environments can introduce abrasive particles that can wear down the seals over time. Stop-and-go traffic or frequent short trips can prevent the engine from reaching its optimal operating temperature, leading to increased wear on the seals.

How to Replace a Faulty Oil Seal

Oil seals are located throughout the engine, meaning that some are easier to reach than others. There are oil seals within the crankshaft, camshaft, valve cover gasket, oil pan gasket, rear main seal, and timing cover gasket. Some of these are more difficult to reach than others. Even visually inspecting these seals can be difficult if you do not have the same tools as a professional automotive technician. As such, some seals should be handled by a professional.

That said, if you are comfortable with working on your own vehicle, here is how you can fix an oil leak that is coming from a faulty oil seal:

1. Preparation

Ensure that you have the necessary tools and equipment, including a socket set, wrenches, a seal puller or pry bar, a rubber mallet, and the new oil seal. It is best to park your vehicle on a flat surface. Open the hood and look for any faulty oil seals. You can also look at the service manual to see where seals are located within the engine.

2. Draining The Oil

After letting the engine oil cool for about 10 minutes, you can drain it out. Place a drain pan under the drain plug and pull it free. Let the oil drain from the tank completely before putting the plug back.

3. Removal of Components

Depending on the location of the oil seal, you may need to remove other components to gain access. This could include removing belts, pulleys, covers, or other parts as necessary. Follow the service manual instructions for the specific procedure.

4. Removing Seals

Once you have access to the oil seal, carefully remove it using a seal puller or pry bar. Be cautious not to damage the surrounding components during the removal process.

Check out this video for some tips on how to remove the seals properly:

5. Cleaning

Thoroughly clean the area where the oil seal sits. Remove any residue or debris, ensuring a clean surface for the new seal to be installed.

6. Installation

Before you install the new seal, apply a thin layer of clean engine oil to the outer edge of the new oil seal to aid in installation and prevent dry starts. Next, add the new seal. Position the new seal in the correct orientation and carefully tap it into place using a rubber mallet or a soft-faced hammer. Ensure it is seated evenly and flush with the surrounding surface.

7. Reassembly

Reinstall any components or parts that were removed to access the oil seal, following the service manual instructions in reverse order.

8. Engine Oil Refill

Once everything is reassembled, refill the engine with the appropriate type and amount of fresh engine oil. Refer to your vehicle’s manual for the correct oil specifications and capacity.

9. Inspection of Leak

Start the engine and allow it to run for a few minutes. Monitor the area around the new oil seal for any signs of leaks. If no leaks are observed, you can proceed with a test drive to further verify the repair.

Should you find that the leak persists, you may have to go to a mechanic to get it repaired. How much will an oil leak repair cost you? It depends.

Final Thoughts on Common Reason For Car Leaking Oil

Now you know the most common reason your car is leaking oil: faulty or worn-out oil seals. Since there are many oil seals within the engine that get worn over time, there is always a chance that they will break and cause an oil leak. Fortunately, you know the signs and how to fix a seal, if necessary. Just keep in mind that some oil seals are going to be complicated to repair, so you may have to go to a service center. Otherwise, consider routinely checking and replacing if you notice wear and tear on the seals.


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