Coolant in Engine Oil Symptoms: Diagnostic Test & Fixes

Written by

Charles Bolte


Vernon Hoppe 

coolant in engine oil symptoms

Is understanding the coolant in engine oil symptoms important? Yes, as doing so will help people to come up with possible solutions to prevent the engine from overheating or, worse, engine failure.

It is impossible to turn back time once an oil and coolant mixing situation happens. Fortunately, car owners can be ready by monitoring the possible signs of this mishap. These signs and diagnostic steps will be featured in this blog.

Signs of Coolant in Oil

Contamination due to water in engine oil is a serious matter to solve, especially since these substances are not soluble. It will only lead to clogging or malfunction since the engine will have a hard time transporting the oil in the engine parts.


There are cases where a mixture of both in an engine results in various errors in the vehicle. That includes the following symptoms that will be discussed below.

1. Cream to coffee color engine oil

The most common symptom that the coolant contaminates a vehicle’s engine oil is the color. Coolant leaking into oil causes the color mixture to change. The coolant usually leaves a hue of green or brown, which results in that shade.


If this situation is not resolved, it will affect the flow lubrication. Since the mixture is thicker, the formed mixture will not travel easily, affecting the function of the engine.

2. Coolant level drops

Meanwhile, oil and antifreeze mixing or coolant can also be noticed when the coolant level drops. The sudden drop indicates that there’s a problem, which can be associated with leakage. However, it is still important to identify whether the leak is internal.


There are cases wherein the coolant level drops while the engine oil level increases. That scenario usually features an oil coolant leak or internal leakage. In short, the coolant leaks into the engine oil, increasing the engine oil’s level.

3. Oil mixture has sweet smell


On the other hand, another situation that confirms the coolant mixed with oil is the scent of the engine oil. Coolants are known to have a sweet smell, and if that familiar scent is present, there is a slight chance the oil is contaminated.

When antifreeze in engine oil happens, the vehicle will likely have a sweet smell. Owners can also verify this by sticking a dipstick in their engine oil.

4. Warning light lights up

In connection with the sudden changes in coolant level, this symptom is also present. The coolant warning sign will light up, signaling that there’s a problem with the coolant. This sign happens due to having a low level of coolant, which can be caused by leakage.


Once this sign is up, it would be best for the vehicle owner to see if the coolant is at the right level. Usually, the drop happens about 0.25% of the amount as it helps to cool down the hot engine. If there’s a change higher than the amount, there must be a problem.

5. Overheats


This last symptom can also be due to engine oil with coolant. A vehicle usually overheats because of low engine oil. It struggles to work, thus resulting in friction in the engine. Due to the clogging of engine oil from coolant, this can happen.

In terms of looking at the low coolant factor, the vehicle can also overheat. As mentioned, coolants keep the vehicle cool and run smoothly. Lacking this support for the engine will result in overheating of the vehicle.

Importance of Monitoring the Coolant and Engine Oil Mixing Symptoms

There are still tons of symptoms that a car owner must know regarding the mixing up of coolant and engine oil. Still, checking the box with just that small list above is a great sign that the vehicle is not performing well and the problem is big.


As a responsible car driver, keeping the passengers safe by ensuring the vehicle is functional is vital. Such problems may risk the safety of everyone, and no one wants to experience that.

Furthermore, the financial aspect is undeniably challenging to face. That’s why, if there are fast solutions that owners can do, it is best to fulfill them right away, thus, helping people to save their wealth and health.

Causes of Coolant in Engine Oil

Previously, several symptoms are featured, showing the possible and ongoing errors that can happen when the 2 substances are mixed. While it can be solved by removing the contaminated engine oil, chances are there’s more to this situation.

Uncovering every part is essential to prevent this mishap from happening again. There can be cases where some parts are busted, which results in the entering of coolant in oil pan.


Causes Potential Risk
Leaky Head Gasket Due to leakage, coolant will seep through and mix with the engine oil.
Cracked Engine Block or Cylinder Head The coolant level will drop rapidly, which could cause overheating.
Corrosive Oil Cooler Corrosion will result in leakage resulting in coolant contaminated oil
Compromised Engine Block Engine blocks are highly durable, but if it gets damaged, most likely it will affect the whole engine.

These causes show that faulty head gasket and others that involve separating the 2 substances will most likely affect the vehicle’s status. Some may result in bigger problems, such as the whole engine of the car.

Diagnostic Process for the Problem

The best way to avoid the list of causes is to ensure that the vehicle is in good shape. It includes checking in and out of the vehicle, which a test can help monitor.

Diagnostic test for coolant in oil


  • Dipstick method – for checking the sweet scent in oil
  • Checking coolant level – a rapid decrease in coolant level
  • Check for leaks – it will involve the oil filler cap
  • Access the valve cover (keeps the engine oil from spilling)

These tests are some of the importafnt steps that car owners must do to verify if there’s at least a small amount of coolant in oil. Doing so will help sort out the main cause of the problem.

Plus, it will help prevent dilemmas once the damaged parts are resolved.

Quick fix options

After the diagnostic part, it will be a lot easier to identify the steps to fix the problem. Usually, it involves the following:


  1. Drain the contaminated engine oil and coolant.
  2. Use a sealant for minimal damages only
  3. Replace faulty parts of the cooler, not only the head gasket, and others, by asking a mechanic to help out

Most of the fixes that need to be done can be technically difficult. That’s why, if the parts of the engine or the coolant are the problem, seek help from a professional.

Frequently Asked Questions


How to tell if coolant is in oil?

Coolant in engine oil is easy to notice, especially if the car owner is familiar with known symptoms. That involves changing color, texture, smell, and engine oil levels.

Furthermore, it involves the rapid change in coolant level, which means leakage. Visit a mechanic right away to help resolve the problem.

What does coolant in oil look like

As mentioned, a color change will occur when both substances are mixed. The common hues are creamy to white and coffee brown.

Can you drive with oil in coolant?

Driving the vehicle despite the problem is possible, but not for too long. It is safe to drive the car to the nearest mechanic store for a diagnostic check up and fix the problem. Other than that, the owner must not drive the car for other purposes.

How much does it cost to repair?

Regarding the cost, a minimal amount is needed to fix the minimal errors. That usually covers the sealant products for the leaks. However, if the engine itself has been damaged, it usually covers up to $8,000 for the expenses.

How often should I check my coolant levels?

Checking on the antifreeze level should be more often. Since the coolant acts as the ingredient for stabilizing the engine during a hot temperature, it is only natural to stock up on the coolant.

The engine may reach a hot temperature but the car should not overheat with the help of the coolant.

Why is there coolant in oil, but no oil in coolant?

Oil in coolant is possible, but it rarely occurs as it will depend on where the leak is. Usually, it happens when the leak affects the lubrication and cooling system of the coolant, which forces oil to go to the coolant.


Oftentimes, a problem may arise with the vehicle if the owner is not maintaining it well. Due to this, the unnoticed deteriorated parts of the vehicle will affect the engine’s performance. Thus, the result affects the coolant and engine oil.

To be fair, it can be caused by an honest mistake; still a responsible car owner must be aware of such situations. That way, it can be prevented before the situation worsens.

Understanding coolant in engine oil symptoms is the best way forward in solving the problem and saving the vehicle from malfunctioning.

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