Why is There Oil in My Radiator? Fixing Way

Having oil in your vehicle’s radiator can cause severe damage to the engine if you fail to detect and fix it immediately. Usually, the various fluids in a car have designated areas of operation; hence, it can pose a serious challenge if there’s a mix-up.

If you’re asking, “Why is there oil in my radiator?” You most likely have one or more failed gasket or seals. There’s more to having oil in your radiator than just a mixture of two different liquids in one place.

Some of the key reasons why oil found its way to your radiator, as well as the symptoms, and solution to the problem, have been unveiled in this article.

oil in the radiator

Why Is There Oil In My Radiator?

Typically, oil in a car radiator indicates that you have one or more failed seals or gaskets, allowing the engine oil to trespass into the cooling system.

Generally, vehicles are built so that the lubrication that comes from the engine oil is different from the cooling system, which helps prevent overheating.

Meanwhile, the head gasket is designed to set a boundary for the oil and coolant to prevent the fluids from leaking into restricted areas so that overheating doesn’t occur. The component also seals a vehicle’s engine combustion chamber to enable it to build the required compression to maintain engine power.

Suppose the head gasket becomes cracked or damaged. In that case, it will no longer be efficient in restricting the fluids to their designated area, thereby allowing leaky oil and coolant to mix in the cooling system which causes bubbles in radiator. An engine overheating incident can also destroy the cylinder head and create an inappropriate seal.

Also, if a car gets involved in an auto crash that damages the engine block or cracks the cylinder head, there’s a tendency for oil to travel into the cooling system, thereby finding its way into the radiator. In that case, you can observe smoke coming from oil cap.

Understanding what causes oil in the radiator will make it easy to implement a corresponding solution to fix the problem correctly. Therefore, if you’re experiencing this kind of challenge, ensure to diagnose the cause or contact a professional auto mechanic to do the job.

Causes of oil in Coolant YouTube

What Happens When Oil Mixes In The Radiator?

Oil mixing with coolant in a radiator can trigger various symptoms. When oil mixes with coolant in your car’s radiator, you will experience overheating and gradual engine wear over time.

If there’s oil in antifreeze, it will be difficult for the fluid to properly lubricate and cool the engine, leading to overheating, which can trigger further engine damage.

If you notice that your vehicle’s temperature gauge is unnecessarily reading too high, ensure to inspect the vehicle’s cooling system and other related components to make sure you don’t have motor oil in radiator, and the coolant is not below the recommended level.

You may also experience coolant in vehicle exhaust if the engine oil and coolant mix in the radiator. If you’re experiencing any of these symptoms in your vehicle, you most likely have a problem to deal with.

Therefore, consult an expert auto mechanic to inspect, diagnose, and fix the problem as soon as possible. However, if you’re a confident DIYer, you can check out the problem and rectify it immediately.

How to Fix Oil in Coolant

Fixing the problem of oil in coolant reservoir is straightforward, depending on the exact cause of the problem. However, the following steps will guide you through the process.

Step 1: Drain the contaminated coolant

First and foremost, ensure to drain the contaminated coolant from the radiator’s drain plug. You can locate the drain plug around the edge at the bottom of the radiator. Usually, you may find it facing the engine on the passenger side.

Before draining the coolant, get a pan to catch the fluid and carefully dispose of the waste according to environmental law prescription.

Step 2: Fix/replace the faulty component

Once you’ve removed the oily coolant from the radiator, now is the time to repair the faulty area or replace the damaged component. If a defective head gasket or seal is the problem, kindly replace the component.

If you discover a crack in the cylinder head or engine block, contact a professional auto mechanic to fix it immediately. Whatever the faulty component, do not move on to the next stage until you replace or fix it.

Step 3: Refill the coolant

After fixing the actual cause of the oil leak, you can now refill the coolant tank with your manufacturer’s recommended antifreeze. Ensure to maintain the maximum level of antifreeze that should be present in the tank.

Kindly note that excessive coolant in the tank can result in another challenge when you’re done. So, make sure you consult your owner’s manual and adhere to the instructions in the booklet.

Step 4: Perform a test run

Finally, it’s time to perform a test run to see if you could resolve the problem. So, ensure to check for any oil residue in the coolant tank.

If there’s any, it’s likely that there is another related faulty component that you’re yet to fix. Otherwise, if there’s none, you are good to go.


Driving with oil in the radiator can damage your vehicle’s engine before you know it. Therefore, do not waste a second before fixing the problem. If you were contemplating, “Why is there oil in my radiator?” The major causes of the occurrence have been exposed in this post.

So, diagnose the problem, identify the exact cause, and fix whatever it may be as soon as possible. Deferring the repair can cause your engine to deteriorate until it finally breaks down completely.

Remember that engine problem are some of the costliest to rectify. So, it would be best to avoid such an experience at all costs.


Mr. Shafiqule Islam is a graduated Mechanical Engineer and has more than 15 years experience of repairing and maintenance of different brand vehicles like Toyota, Mitsubishi, Ford, Mercedes, BMW etc. He is also giving training to Mechanics. He has started writing to share his practical knowledge to Vehicle Owners, Drivers and Mechanics to keep their cars at best fit.

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