Coolant in oil usually happens because of a blown head gasket, cracked engine block, or damaged oil cooler. Common symptoms include milky oil, white exhaust smoke, overheating, coolant loss, and engine performance problems.
Two of your vehicle’s most vital fluids are oil and coolant. They guarantee the life of your engine if all parts are carefully monitored and maintained regularly. One sign of trouble, for example, is coolant in oil. There are a few different ways that coolant in engine oil can leak into the motor’s oil, but before that ever occurs, you should also become familiar with the coolant in oil symptoms. When you know what to look for, you can prevent an even more severe problem from happening to your engine, such as loss of power, lack of lubrication, or total engine failure.
Signs And Symptoms of Coolant in Oil
One of the first signs of coolant in oil can be found when you are checking your oil level. When you look at the dipstick, and the fluid appears to be rather milky, you might have coolant in engine oil. Here are other coolant in engine oil symptoms to watch for.
Coolant Loss
One imperative sign involves having a constantly decreasing level of your coolant, but without any leaking from underneath the car onto the pavement or coolant dripping out of the exhaust pipe. Also, if you find that you must add more than a pint of coolant during each oil change, that is not normal. It’s a sign that your cooling system is in trouble. Because this system could be compromised, and you don’t see the coolant coming out of the car, then it’s mixing with the oil.
Syrupy, Sweet Smell
When you check the oil, you may notice that it has a musky, earthy smell. Conversely, coolant smells extremely sweet, almost to the point of being unbearable. Therefore, you can easily tell the difference between the odors of each fluid. With that in mind, when you go to check your oil, and you smell even the slightest hint of something sweet on the dipstick, you have coolant leaking into your oil. This is another way to find out for sure if the coolant is mixing with the oil, even after noticing the drop in its levels without any external leaks.
Milky Color
Aside from the difference in odor, you’ll see a change in your oil’s color and consistency if it mixes with the coolant. By itself, oil always looks dark and has a thick consistency. Once the coolant starts leaking into the crankcase, however, you’ll see a small stream of orange, green, or red floating in your oil. Unfortunately, if you run the engine, the crankshaft and oil pump will mix the two fluids together into what’s called “the dreaded milkshake.” The mixture gets its name from its resemblance to a chocolate milkshake on the surface. At this point, this gooey mixture has already circulated the engine’s pathways, leading to a bearing that was demolished beyond repair due to a lack of lubrication.
Puff Of White Smoke
Also, if you see white smoke puffing out of the exhaust pipe, and it has a strong, sweet odor, this tells you that you have coolant in engine oil. You might even see an increase in your oil’s level when this occurs, but this points toward a large amount of coolant entering the crankshaft along with the oil. In this situation, you should immediately turn off the ignition
What Causes Coolant to Mix with Oil?
Although engines are designed in such a way that coolant would never mix with oil, there are mishaps that cause this to happen. These issues are also common in antifreeze in oil and can lead to serious engine damage if ignored.
Leaking Head Gasket
The cylinder head, which is located at the top of the engine’s block, has a head gasket that seals off the area between the head and the block. If this seal fails even slightly, coolant can leak into the oil.
Overheat
Overheating causes damage to the head gasket, which breaks the barrier between the oil and the coolant. Thus, they circulate through the wrong pathways and mix.
Damaged Oil Cooler
In the case of some vehicles, the oil cooler is surrounded by a larger chamber that holds the coolant. As the oil cooler circulates the oil, the separate coolant chamber keeps the oil’s temperature down. However, if the oil cooler is damaged, then you can have coolant leaking into the oil.
Faulty Radiator Cap
A faulty radiator cap can also be one of the overlooked antifreeze in oil. When the cap fails to maintain proper pressure in the cooling system, it can lead to coolant overflow or improper circulation. This imbalance may force coolant into areas where it doesn’t belong, including the oil system. Replacing a damaged radiator cap is a simple and inexpensive fix that can prevent further contamination.
Damaged Engine Block
Blocks can last for many years and are almost foolproof. However, if you don’t change the oil often enough, the block can crack. This also leads to the coolant leaking or poor coolant circulation.
How To Fix Coolant in Oil
First off, if you suspect that coolant in oil is present, do not drive the vehicle. Turn off your car immediately, or refrain from turning on the ignition. This keeps the mix of fluids from circulating and causing serious damage to your engine.
Next, it’s best to drain and flush the system to remove any contaminated oil or coolant from the engine. This helps prevent further corrosion or buildup inside the engine components. After that, change the oil and filter to make sure any remaining traces of coolant are cleared from the system.
One possible fix is to apply a sealant on the radiator, but that may not address the issue of a damaged head gasket or a broken oil cooler. The ideal route toward fixing this problem is to allow a mechanic to look under the hood and diagnose the cause. Anything related to a damaged oil cooler or a gasket that needs replacing should be done by a licensed professional. Plus, another thing to keep in mind is that a mechanic would have the proper equipment to check for further damage, like a cracked engine block. If that is the case, then you will need a whole new engine—or a new vehicle.
To prolong the life of your car, you need the best fluids that enhance its functionality while performing the two most important tasks—cooling the engine and lubricating it. Shield Lubricants are the leading producers and worldwide exporters of top-performing oil, lubes, and coolants. Your vehicle is one of your most important investments. Therefore, using products that have been certified and proven to lengthen their life and keep them running smoothly will save on costly repairs and keep your engine safe from major malfunctions.
Are you not sure if your engine’s fluids are up to par? We also offer testing on your lubricants, with results sent to you 3 days after receiving your sample. Find out more about our products for the industrial, automotive, and marine industries by contacting Shield Lubricants.
Can You Drive With Coolant in Oil?
Driving with coolant in oil is extremely risky because the contaminated oil loses its lubricating ability. As the coolant mixes with engine oil, it creates a thick sludge that cannot properly protect internal engine components from friction and heat.
Even driving for a short distance with coolant-contaminated oil can damage crankshaft bearings, pistons, camshafts, and other critical components. In severe cases, the engine may seize completely, resulting in very costly repairs or full engine replacement.
If you notice milky oil, white exhaust smoke, overheating, or coolant loss, stop driving immediately and inspect the vehicle before further engine damage occurs.
What Happens If Coolant Mixes With Oil?
When coolant mixes with oil, the lubrication system becomes contaminated and loses efficiency. Engine oil is designed to reduce friction and remove heat, but coolant contamination changes the oil’s viscosity and creates sludge deposits throughout the engine.
Over time, this can lead to:
- Bearing failure
- Increased engine wear
- Overheating
- Corrosion inside the engine
- Reduced oil pressure
- Complete engine failure
The longer the contaminated oil circulates, the more severe the internal damage becomes. Early diagnosis is essential to prevent expensive repairs.
Frequently Asked Questions
What color does oil turn when coolant mixes with it?
When coolant mixes with engine oil, the oil usually turns milky brown, creamy, or foam-like due to contamination.
Can low coolant cause milky oil?
Low coolant itself does not directly cause milky oil, but coolant leaks inside the engine can contaminate the oil.
Is coolant in oil expensive to fix?
Yes. Repair costs vary depending on the cause. A radiator cap replacement may cost very little, while a blown head gasket or cracked engine block can cost significantly more.
Can an oil change fix coolant in oil?
No. An oil change only removes contaminated oil temporarily. The underlying coolant leak must be repaired first.
