Oil in the coolant reservoir
Modern engines depend on proper fluid flow, but mixing of oil and coolant can cause big problems. Oil in the coolant reservoir indicates contamination that affects efficiency.
But the question arises: “Is it time to panic?” We’ll answer this question and show you how to repair oil contamination in your cooling system and restore proper flow.
What does oil in coolant look like?Oil and coolant don’t mix well. This causes a noticeable change in the condition of the coolant and oil that it comes into contact with.
Coolant contaminated with oil often takes on a viscous consistency and appears gray or brown in color. This becomes more noticeable the more contaminated it is.
If your engine’s cooling tank is contaminated with oil, it may look cloudy at first. Over time, a milky film may form inside the container itself, obscuring your overall visibility. In the worst case scenario, this mixture may even leak out from under the overflow tank lid.
What happens when oil gets into the coolant? When oil gets into your engine’s coolant, it can have several effects. Most notably, it severely reduces the engine’s ability to protect itself from overheating.
Over time, cross-contamination between oil and coolant clogs various cooling channels, preventing proper heat exchange. Additionally, if oil does occur in the engine’s cooling system, the possibility of coolant contaminating the engine’s lubrication system should not be overlooked. This type of contamination can have devastating effects on bearings and other critical surfaces in the engine.
Oil in coolant and coolant in oil
Ideally, engine oil and coolant should never mix. These fluids circulate in close proximity to each other at some points along their path, but they should always be structurally sealed from each other.
However, under certain circumstances, one or more problems can cause oil to contaminate the coolant or coolant to contaminate the oil. When oil gets into your engine’s cooling system, it often clogs various cooling channels, including those in your vehicle’s radiator. This can reduce your engine’s cooling performance to less than ideal levels.
Conversely, when coolant gets into your engine’s lubrication system, it effectively reduces the oil’s viscosity, making many vital components vulnerable to accelerated wear.
Possible Causes of Oil in the CoolantThere are several reasons why oil may appear in your vehicle’s coolant reservoir. None of these situations are ideal and require timely intervention to prevent excessive engine damage. Understanding the possible causes of this contamination can help you get your vehicle back in working order quickly. Below are some of the most common ways oil can get into your engine’s cooling system:
1) Leaking Cylinder Head Gasket
The most common cause of oil contamination in your vehicle’s coolant reservoir is a blown cylinder head gasket. Your engine’s cylinder head gasket seals each cylinder head from the engine block itself.
This seal also prevents the mixing of oil, coolant, and compressed gases. A leaking head gasket can also be the cause of your car leaking oil even if there is no visible oil leak.
2) Cracked cylinder head/block
In rare cases, damage can occur to the actual component sealed by the head gasket, such that it cracks, allowing the coolant and oil to mix freely. This type of structural failure can occur in both the engine block and the cylinder head, and in most cases will require a complete replacement.
3) Damaged heat exchanger or oil cooler
Today’s vehicles often have a series of heat exchangers that are specifically designed to cool the lubricating oil to an acceptable level. Some vehicles have an oil cooler, but many also use a transmission oil cooler. An internal leak in any of these components can cause the oil to mix with the vehicle’s coolant.
4) If the coolant reservoir is filled with oil incorrectly
This scenario may seem a bit far-fetched, but fluids are poured into the wrong containers by well-meaning people far more often than you might think. Nonetheless, corrective action should be taken.
What to do if you find oil in your coolant reservoir?
First, you need to address the root cause of your engine’s oil contamination. Of course, this includes diagnosing the problem at hand. This is most often done using a cooling system pressure tester while checking for leaks. If the pressure drops during such a test but no external leaks are found, the seals may be faulty.
Once a leak is found, appropriate repairs should be made and all oil residue should be removed from the cooling system. Many commercial cooling system flushers are offered for this purpose, but some consumers use alternatives such as dish soap instead.
Additionally, it is recommended that you remove your vehicle’s coolant reservoir before cleaning it by hand, if possible.
