How to Fix Coolant Mixing With Engine Oil?

October 23, 2021

Coolant in the engine oil.

There may be an issue with one of your engine’s gaskets or seals if oil is found in the coolant or vice versa. In order to prevent your vehicle from overheating, your engine is equipped with separate systems for controlling engine oil and coolant. When coolant or oil leaks into one another, the cylinder head seal, sometimes referred to as the head gasket, seals the leak. On the occasion that your head gasket has been damaged or cracked, you may anticipate your oil and coolant to begin mixing with one other.

Additionally, oil and coolant may mix when your engine overheats and breaks or fractures the head gasket or cylinder head. Oil and coolant can mix in an accident involving a cracked cylinder head or engine block damage. We often hear from consumers who are experiencing this issue.

Major Causes of Oil in the Coolant

If leakage has been present for a long period of time, the most typical visible sign to look for is brownish milky sludge in the coolant. A glossy oil may appear on top of the coolant as the leak occurs. If the owner didn’t notice these signs, the car might have overheated due to improper maintenance.

The coolant will have to be drained and replenished if it has been contaminated with oil or grease. Additionally, it will be necessary to address the underlying issue. 

Typical sources of oil in the coolant are as follows:

A Blown Head Gasket

Oil can seep from a blown head gasket into the cooling system, where it will subsequently mix with the coolant and cause contamination. As a consequence, the radiator and coolant reservoir have brown muck on top. Additionally, coolant may seep into the combustion chamber. It will produce a sweet white plume of exhaust as a reaction.

The good news is that repairing an oil cooler leak is considerably less costly for the consumer. You will require to replace the oil cooler and its gasket. It will also be necessary to flush and re-fill the cooling system.

Using a compression test, you can determine whether or not your head gasket has blown. You may require some repairs if the head gasket is blown, including:

  • Naturally, you’ll have to get a new head gasket.
  • It will be necessary to flush the entire cooling system.
  • Check for leaks or damage in the radiator and water pump. Cool oil has a thicker consistency than water. If you run the radiator and the water pump with cold oil, it may cause damage.
  • An oil cooler that isn’t working properly.
  • When it comes to gasoline-powered cars, oil coolers are not prevalent. However, turbocharged engines are more likely to have them. Typically, when the oil cooler malfunctions, the most noticeable indication is an oil accumulation in the coolant. It may lead some to believe that the head gasket has blown. In most cases, a blown head gasket will degrade the engine’s power. Even if the oil cooler leaks, the engine will continue to run smoothly.

Transmission Cooler Leakage

Transmission coolers are commonplace in cars equipped with an automatic transmission and often included in the radiator. It may lead to transmission fluid leaking into your coolant because of radiator-to-cooler cracks and the coolant turning pink and foamy in appearance. Unfortunately, the coolant can get into the transmission and may be severely damaged to the point that it requires replacement.

Steps on How To Handle Leak Of Coolant In Engine Oil

If your car’s coolant leaks even a little bit, it may cause an overheat and ultimate failure. You’d be stuck in the middle of the highway if this happened. Nevertheless, if the coolant did manage to seep into the engine oil, the resulting damage would be costly to fix.

Step 1: Inspect the Engine for Coolant for Any Leakages

As an outcome of the coolant-to-oil mixing within the engine, a color of a milky white or yellow oil is formed, which some call chocolate milk. It is visible when the oil dipstick on the valve cover removes.

You may also peek under the valve cover with a flashlight to see any coolant in the oil. Condensation may produce a tiny bit of milky oil that appears on the oil fill cap, although this is not common in engines used often. Head gasket failure is almost often to blame when this problem arises.

The intake manifold gasket on V6 and V8 engines can seep, letting coolant seep into the engine’s crankcase and mix with the engine oil. You will need to remove the intake manifold and inspect the gaskets to rule out this failure source.

Another frequent issue that allows coolant into the engine oil is a blown head gasket. Sealing the engine block from the cylinder heads as well as controlling coolant pressure and cylinder combustion are done by this gasket. When this gasket is subjected to high temperatures and pressures, it is more likely to fail.

In order to find out whether the head gasket has failed, there are several various tests you may do. An engine with a cracked cylinder block or head is one of the more common issues. In most cases, this will happen after the engine has been repeatedly overheated, allowing cooling fluid to enter the engine oil.

It is necessary to dismantle and inspect the engine to assert whether this issue has happened. 

Step 2: Inspect the Presence of Motor Oil in the Coolant

Your vehicle’s engine and automatic transmission are protected against overheating by two types of coolers while the car is in motion. External oil coolers are equipped on specific engines, and radiator coolant is circulated through them to help maintain engine coolness. This cooler is critical because if it malfunctions, the engine oil will be injected into the coolant, which will then be pumped back into the radiator.

Removing the radiator cap will allow you to check for this problem after the engine has cooled down. If you look inside the radiator, you’ll notice oil slicks. Furthermore, coolant may leak into the engine oil due to this fault even with the engine idle. Despite not having an engine running, pressure remains in the cooling system. There’s a chance you’ll find motor oil in there as well. In order to fix this problem, a new oil cooler should be replaced along with a complete flush of the cooling system.

Step 3: Look for Transmission Fluid in the Radiator

Transmission fluid is channeled through a cooler that is housed inside the radiator to prevent overheating. Using this hydraulic fluid cooler, you can ensure that hydraulic fluid stays at appropriate temperatures. Once this cooler creates a leak, transmission fluid will run into the radiator. Engine overheating and transmission problems are possible outcomes of this. Radiator replacement and transmission fluid replacement are required when this issue arises.

How Much Is The Cost Of Repairs and Replacement?

The short-term repair costs, the cost of new fluids, and leak-stopping products are not too expensive. Nevertheless, repairing the faulty gasket or component, in the long run, maybe much more costly. Your engine block may have a crack, and that is the disaster situation you want to avoid. There is nothing that can be done if this is the case other than to change the engine, which usually costs around $4,000 and $8,000. It is, once again, the worst-case situation that might happen.

The cost of replacing the radiator and repairing the transmission should not be more than $400 or $500 if the problem is limited to these two components. The cost of replacing a head gasket, on the other hand, might reach thousands of dollars, including materials and labor.

The Bottom Line

Mixing coolant with oil is a catastrophe waiting to happen. In most cases, it indicates the breakdown of a critical component inside your engine system. Overheating and increased engine wear are both caused by an oil or coolant mixture that travels rapidly through the engine.

If you add oil to the coolant, you’ll have to do an oil and coolant flush right away. A flush entails draining and replacing the vehicle’s coolant and oil. It will be necessary to repair the defective component to prevent an oil or coolant mixture from occurring again.