How to fix oil in coolant reservoir

Are you having engine troubles due to an oil in coolant mix? Don’t panic, fixing the issue might be simpler than you think. In this blog, we’ll show you how to easily and safely fix the oil in your coolant reservoir – so it won’t affect your car’s performance! Ready to take back control of your vehicle? Let’s get started.


If you’ve noticed oil in your coolant reservoir, it could be a sign of a serious problem with your engine. The presence of oil in the cooling system suggests that the engine oil and coolant are mixing, potentially causing engine damage and performance issues.

Generally, the most common causes of oil in the coolant reservoir are a blown head gasket, a cracked engine block or head, or a damaged cylinder head gasket. As soon as you discover oil in the coolant reservoir, it’s essential to diagnose and fix the issue as soon as possible to prevent further damage to your engine.

Attempting to fix this issue yourself can be dangerous and complex, and it’s highly recommended that you seek professional help in diagnosing and fixing the problem. Even a small mistake can lead to significant engine damage, resulting in costly repairs.

What is an Oil in Coolant Reservoir?

Oil in coolant reservoir is an indication of a serious issue with your engine that needs immediate attention. It could indicate a blown head gasket, a cracked cylinder head, or an engine block.

Here’s how you can fix the problem:

  1. Step 1: Identify the source of the problem. Check for signs of coolant in the oil, power loss, or excess smoke from the tailpipe. If you detect any of these symptoms, it’s best to take your car to a certified mechanic.
  2. Step 2: Once the source of the problem is identified, drain the coolant and dispose of it safely. Refill the coolant with a fresh supply and run the engine for a few minutes to circulate the coolant.
  3. Step 3: Flush the coolant system to remove any contamination, including oil, rust or dirt particles.
  4. Step 4: Replace the oil and oil filter with a fresh supply to prevent further contamination of the coolant system.

It is important to address oil in coolant reservoir as soon as possible, as it could lead to more severe engine damage or malfunctioning.

Pro Tip: Regular car maintenance and inspections can prevent serious engine problems such as oil in the coolant reservoir.

Causes of Oil in Coolant Reservoir

Oil in your coolant reservoir can be caused by several factors that can range from minor issues to serious engine problems. Here are the main causes of oil in coolant reservoir and how to fix them:

  • Engine Oil Cooler Failure: The engine oil cooler can crack or develop a leak, allowing engine oil to mix with coolant. The fix is to replace the damaged oil cooler.
  • Cylinder Head Gasket Failure: A damaged cylinder head gasket can cause oil to seep into the coolant passages. Replacing the faulty gasket is necessary to avoid further damage to the engine.
  • Cracked Engine Block: A cracked engine block can cause oil to contaminate the coolant. Replacing the engine block might be necessary to fix the problem.
  • Transmission Fluid Cooler Failure: If the transmission fluid cooler inside the radiator is damaged, it can cause the transmission fluid to mix with the coolant. To fix the issue, the transmission cooler needs replacement.

In conclusion, fixing oil in the coolant reservoir depends on the underlying cause. It’s important to have a professional diagnose the issue and conduct the repair to avoid further damages to the engine.

Symptoms of Oil in Coolant Reservoir

When you see oil in your coolant reservoir, it may be an early indication of bigger engine problems. To fix it, you should look out for these symptoms:

  1. White smoke or steam coming from the exhaust pipe.
  2. The engine overheats frequently.
  3. The coolant changes color and appears milky or creamy.
  4. The engine oil changes texture, appears thinner, foamy, and lighter in color.

If your vehicle is exhibiting any of these symptoms, take it to a professional mechanic to check for issues like a blown head gasket, a faulty engine oil cooler, or transmission cooler. Ignoring this problem can lead to a complete engine breakdown.

Pro tip: Regular maintenance checks can help detect such issues at the earliest and save you from huge repair costs in the long run.

Diagnosing Oil in Coolant Reservoir

Noticing oil in the coolant reservoir of your vehicle is a sign of a serious problem, and it can be caused by a number of reasons such as a blown head gasket or a cracked engine block. However, identifying the root cause of the problem is crucial before you can proceed with fixing it. Here are some diagnostic steps to follow:

  1. Check for any signs of a blown head gasket or a cracked engine block.
  2. Inspect the engine oil and the color and consistency of the coolant for any signs of contamination.
  3. Pressure test the cooling system to check for leaks or any other anomalies.

Once you have identified the root cause, you can proceed with the repair. A head gasket replacement or an engine rebuild is recommended for severe cases, while a simple flush and fill of the coolant system can fix some mild issues. Always consult your mechanic for an expert opinion on the best course of action.

How to Fix Oil in Coolant Reservoir

Finding oil in your engine’s coolant reservoir can be a worrying sight, but fortunately, it’s a problem that can be fixed. Here are some steps to help you fix oil in the coolant reservoir:

  1. Identify the source of the problem: The presence of oil in the coolant reservoir could indicate a cracked head gasket or a damaged engine block. Check for other symptoms such as overheating, white smoke from the exhaust, or low oil pressure.
  2. Drain the coolant: Using the radiator drain plug, drain the coolant from the engine.
  3. Flush the system: Use a flushing agent to clean out the engine block and radiator. Follow the product instructions for the best results.
  4. Inspect the head gasket and engine block: If the head gasket or engine block is cracked, it will need to be replaced.
  5. Refill the coolant: Once you’ve fixed the problem, refill with the recommended type and amount of coolant.

It’s important to address oil in the coolant reservoir promptly to avoid further engine damage.

Pro tip: A cracked engine block or head gasket is a serious issue that requires professional attention. Don’t attempt to fix it yourself unless you have the necessary expertise.

Preventative Maintenance

Preventative maintenance is essential for ensuring the optimal functioning of your vehicle. However, if you notice oil in your coolant reservoir, it is a sign of a serious problem that requires immediate attention.

Here is how you can fix oil in your coolant reservoir:

  1. Identify the root cause of the problem. It could be due to a blown head gasket, a damaged cylinder head, a cracked engine block or a damaged transmission cooler.
  2. Drain the contaminated coolant and dispose of it safely.
  3. Flush the cooling system thoroughly with a cooling system cleaner and water.
  4. Replace the damaged head gasket or other affected part.
  5. Refill the coolant with a fresh mixture of coolant and water in the correct ratio, as specified by your vehicle’s manufacturer.
  6. Bleed the air from the cooling system, according to your vehicle’s manual.
  7. Start the engine, let it run until it reaches normal operating temperature, and check for leaks.
  8. Perform a complete system check to ensure all components are functioning normally.

Pro Tip: Regular inspection and servicing of your vehicle can help prevent costly repairs and keep your car running smoothly.


To conclude, if you notice oil in your coolant reservoir, it is a sign of a major problem that needs immediate attention. The oil may indicate a leak in your head gasket or engine oil cooler, which can lead to engine failure if left unresolved. It’s recommended to take your vehicle to a professional mechanic to diagnose the issue and provide a suitable solution as soon as possible.

In some cases, you may need to replace the damaged components or perform extensive repairs, which can be costly. However, ignoring the problem can lead to even more significant damages and expenses. So, act quickly and get your vehicle examined by a mechanic to ensure its longevity and safety on the road.


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