Coolant in Oil: Symptoms, Causes and Fixes

Have you ever checked your motor oil and noticed a milky liquid on your dipstick? If yes, it means that you have internal oil leaks. If you see coolant mixing with oil, you have to act fast because it can cause severe engine damage. If you ignore this issue for a long time, it can damage your entire engine system. To prevent this, once you notice coolant in Oil, you have to fix it immediately or seek professional help.

In this article, we’ll discuss at length coolant in oil symptoms and how to fix it.

How do I know if there is coolant in Oil?

Motor oil mixing coolant indicates head gasket or engine failure. When antifreeze mixes with motor oil, it reduces the oil viscosity and lubricating power, resulting in loss of engine power and lubrication, leading to engine damage. There are a few factors to watch out for that indicate water in engine oil Symptoms.

Coolant in Oil

Coolant Loss: If you notice continuous antifreeze drops but there are no leaks from the exhaust pipe or on the ground, odds are the antifreeze is making its way to the oil crankcase. So, if you notice frequent antifreeze drops, ensure you inspect for leaks. If you find no coolant leaks, you can check the oil level to see if the oil is getting into the crankcase.

Sweet smell: when you notice a coolant leak without drooping on the ground or any visual on the engine bay, chances are the coolant has missed its passageway to the oil pan. Antifreeze in oil has a sweet smell. Another way you can tell if there are antifreeze and oil mixtures is to pull the dipstick and whiff it. Even a small amount of coolant in oil will give a sweet smell.

Milky Colour:  When antifreeze first gets into the oil pan, it’ll leave an orange, red, green, or brown fluid in the crankcase, depending on the coolant your vehicle utilizes. However, as the engine runs over time, the coolant and oil will mix, forming a milky liquid. The mixture of these two fluids will gum up the engine passageway, which indicates a ruined engine. So, when you pull your dipstick and notice a milky Colour, it tells you there’s a coolant-oil mixture.

Note: there is a normal coolant loss, so you don’t have to bother when you notice a coolant loss once in a while.

oil mix with coolant

What causes coolant in the oil

There are many factors that should be taken into place – in considering what causes coolant in the crankcase. Let’s briefly look at the causes one after the other.

A cracked head or blown head gasket: The most common area for coolants to get into the crankcase is a cracked cylinder head or blown head gasket. When you have a lousy head gasket, you will notice smoke from the exhaust pipe. Usually a white smoke. If you don’t have any other symptoms but have a coolant and oil mixture, there are other places that it could be coming from.

Oil Cooler: Another place that is not very common but is possible is your oil Cooler. The oil Cooler is designed to accommodate both oil and coolant in a separate compartment, and your air Cooler could have small internal cracks that could be the cause of the problem you are experiencing. If your oil cooler fails, you will get oil in the Coolant but no coolant in the Oil.

Leaky Gasket Head: The head cylinder gasket is a gasket that sits between the cylinder head and engine block to prevent water (antifreeze) from mixing with the motor oil. When you have a blown head cylinder gasket, or it begins to leak, it will eventually mix Coolant with the engine oil, which could cause  Overheating.

The oil and coolant mixture is a symptom of a blown head gasket and needs to be replaced. You can get a head gasket tester kit from any local shop around you or online and see if the issue is the head gasket.

Suppose the tester kit confirms that you have a damaged gasket. In that case, you may want to contact a professional mechanic to assist you in carrying out the replacement unless you are a mechanical engineer with field experience. This requires removing the timing and the head cylinder before you can access the head gasket to replace it. The average replacement cost of the head gasket is $1000.

Overheating: if you have an Overheating engine, it can cause your head gasket to be damaged, which could be the reason your antifreeze and motor oil are mixing. Once you have a damaged head gasket resulting from an engine Overheating, it will allow motor oil and coolant to pass the wrong pathways.

Damaged Engine Block: A damaged engine block could possibly cause engine oil to mix with antifreeze. This is the least scenario that can happen because engine blocks are resilient. If you have a damaged engine block, your best bet is to get another engine or replace the engine block. You can get another block from an online or local scrap yard to rebuild your engine so that it can function well again.

Coolant in Oil

How to fix coolant in Oil

Depending on what you think is the issue, you can face it or seek professional assistance. The cause could be due to engine Overheating, leaky head gasket, or oil cooler. The most common is a leaky head gasket. So, if you are asking how to fix coolant mixing with engine oil, especially when the fault is a leaky heady gasket, you have two options. You can either let a mechanic help you pull off the head gasket and replace it and the other damages that it must have done inside, or you can try putting a steel sealant in the radiator and have it do the fix all the way.

If you don’t have enough money to pull off the head gasket and replace it, you can go for the second option because fixing a head gasket leak could be pretty expensive, depending on your car model. However, the second option would be just a temporary fix. If you choose to go with the steel seals, I will show you how to do it correctly.

To begin with, you want to have a clean coolant in the radiator. If your coolant is dirty, you have to flush it out and pour in a new coolant. Then, you want to take out the two bolts in the thermostat housing and remove the thermostat. Then, bolt the thermostat housing without the thermostat in it. With the thermostat out, the sealant will flow well and have a better chance to seal the leak.

You may want to take off the spark plug coils and loosen the spark plugs. If you find coolant on any of the spark plugs, it shows that coolant is leaking in that same cylinder. This trick has been working for me for years now. If you find coolant on any of the spark plugs, you will have to tighten other spark plugs and leave that one open. You may have to unplug that cylinder injector so it doesn’t fire.

  • Grab the steel seals and pour them into the radiator and start up the car. It will be making a lot of noise because there is no spark in the hole.
  • Let the engine idle for about 30 minutes to let the sealant do its work.
  • After 30 minutes, Shut off the car.
  • Let the engine cool down for about 30 minutes, and then repeat this process 3-4 times and when you’re finally done.
  • Let it dry overnight without the spark plug in the hole.
  • Do not forget to put back the thermostat.

The next morning, put the spark back in the hole and tighten it. Now you want to run the car without accelerating it much to let the sealant get a better chance to circulate very well. And that is it. Unfortunately, some gasket holes are too big for the sealant to work. But, in many cases, this is the best first option. Bringing the engine down is an expensive job.


What happens if you put coolant in Oil?

Suppose you accidentally put coolant in engine oil, or the coolant mixes with the oil for any reason. In that case, it will cause the engine oil to lose its viscosity and lubricating power, resulting in overheating, if ignored, which could lead to catastrophic engine damage. Once you notice coolant mixes with oil, you have to turn off your engine, inspect the cause, or contact your mechanic for a proper diagnosis.

Can you drive a car with oil in Coolant?

Coolant and oil have different compartments in the engine and should never mix. Driving a car with a coolant and oil mixture can cause severe issues in your engine, which could lead to expensive engine repair or total engine replacement.

What does the oil look like with a blown head gasket?

As you know, oil and coolant are not meant to pass through the same route. Both have different compartments. When coolant finds its way to the crankcase, regardless of the coolant color, the motor oil will change color within a short period. If you dip in and pull your dipstick, you will see a milky color. The milky color is one of the coolants in oil symptoms.

Can a bad water pump cause coolant in Oil?

Water pumps are designed to pump water through the radiator, water hose, engine, and entire cooling system. A bad water pump cannot cause coolant to mix with oil. However, the Coolant and oil mixture can be caused by a broken radiator causing coolant to mix with oil or via a blown head gasket.

How bad is oil in Coolant?

Whether you find coolant in oil but no oil in coolant or just notice oil in coolant, it indicates a problem within your engine compartment. You have to find the cause of this problem and fix it immediately. Failure to address this issue on time will lead to catastrophic engine damage.

Final word

If you notice coolant in the oil, it is not the end of the world. But you should know that repairing it should cost you over $1000, depending on the ultimate cost of the problem. If the case is from the oil cooler, this could be an easy fix. If you’re a DIY enthusiast, you can fix it without contacting a mechanic.

If you confirm that the head gasket is the culprit, you can first try using a steel seal by following the instructions above – if it fails, you will have to contact a mechanic to pull off the head cylinder and replace the head gasket.

Hopefully, you have found information on how to tackle this issue if you end up one day finding yourself in this situation.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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