Coolant in Oil – Symptoms, Causes & What To Do

There are lots of problems you expect when you’re looking at your vehicle, but coolant in the oil probably isn’t one of them. But the truth is that it’s more common than you might think!

If you have coolant in oil, then you very likely have a blown head gasket. We’ll walk you through everything you need to know about diagnosing and repairing the problem for you here.

How You Find Coolant in the Oil

Unless you’re in the habit of constantly looking at your dipstick, you might not even notice that there is coolant in your oil for a little while. But that’s why it’s important to know a few warning signs and what to look for when you’re checking out the oil.

By far the most obvious warning sign of coolant in your engine is an overheating engine. Unfortunately, this happens because the coolant doesn’t dissipate heat from the engine in the same way oil does.

Unfortunately, this problem is more likely to happen when you drive your vehicle for a while, so there’s no telling where it can leave you stranded.

The first sign many people notice when there’s oil in the coolant is that there’s not enough coolant in the coolant reservoir. Coolant is a sealed system, so you shouldn’t need to keep topping it off. If you do, that means the oil is going somewhere.

If you look for an external leak and don’t see anything, one of the next places you should check is the dipstick.

When you’re looking at the dipstick, there are a few things you’re looking for. First, if the oil appears a milky color, this is a tell-tale sign that there’s oil in the coolant. Not only that, but if it’s already a milky color there’s a lot of oil in the coolant.

Next, see if the oil has a sweet smell. Coolant smells sweet while oil doesn’t. So, if you can pick up a sweet smell from the oil and there’s coolant missing from the reservoir, there’s a decent chance there’s coolant mixing into the oil.

This is also something you can check when you’re changing the oil. If you notice a milky or creamy color from the oil or a sweet scent as you drain the oil we highly recommend replacing the head gasket before completing the oil change.

Otherwise, you’ll have to re-accomplish the entire oil change when you replace the head gasket.

Cause of Coolant in Oil

While some guides try to tell you a dozen different reasons there might be coolant in your oil, we’ll keep it simple for you here. If you have coolant in your oil there’s a 99.9 percent chance that you have a blown head gasket.

In fact, the chance is so high that when most mechanics see this problem they don’t even look for anything else. Really, don’t overthink it. If there’s coolant in your oil, your vehicle has a blown head gasket.

What Can Coolant in Oil Do?

If there’s coolant in your it’s not a problem you’ll want to ignore. Not only does it mean that there’s a blown head gasket in your vehicle, but coolant doesn’t work anything like oil.

Because of this, one of the first signs of damage from coolant in the oil is an engine that overheats. That’s a major problem for many reasons, and if you ignore it for too long it can lead to severe engine damage.

Moreover, even if you’re keeping the engine from overheating, coolant doesn’t have the same lubricating properties as engine oil. This means there will be more friction between parts. Not only does this friction create heat, but it also causes them to wear out quicker.

What To Do if Coolant Is in Oil

If there’s coolant in your oil, the first thing you need to do is stop driving your vehicle. While a quick trip to the repair shop to drop off your vehicle is probably fine, we wouldn’t recommend anything else.

The more you drive the vehicle, the more you’re wearing down various components in your vehicle whether you see it or not.

Next, you need to either take the vehicle to a repair shop or get the parts on order to repair it yourself. Either way, it’s time to replace a head gasket!

Cost To Fix

When you find something wrong with your vehicle, one of the first things you want to know is how much it will cost to fix it and get it back on the road. If you’re taking your vehicle to a professional repair shop replacing the head gaskets will cost you quite a bit.

Typical costs to replace head gaskets for your vehicle range from $1,700 to $2,200 for both parts and labor. But if you’re mechanically inclined, the good news is that most of this cost is labor.

In fact, typically between $1,000 and $1,500 of the repair cost comes down to labor. So, if you can do the job yourself you can save a lot of money. It is a labor-intensive job, though, so you’ll need to dedicate a good portion of your day to it.

If you’re using aftermarket parts, expect to spend between $50 and $300 for all the necessary gaskets, and then get the necessary oil, oil filter, and coolant to refill everything back up in your engine. When you total everything up it should cost between $200 and $500 if you do the job yourself with aftermarket parts.

How To Replace a Blown Head Gasket

You can save a lot of money if you replace your blown head gaskets yourself, but it’s a labor-intensive job. But because the savings are so high for this relatively common problem, we wanted to walk you through everything you would need to do to replace your vehicle’s head gaskets.

Before you start tearing apart your engine gather all the necessary supplies. You’ll want new coolant for your vehicle, oil, an oil filter, and the entire head gasket kit for your vehicle.

Don’t purchase just the head gasket unless you already have all the other necessary gaskets on hand. When you’re tearing down the engine to the head gaskets, you’ll need these other gaskets. Additionally, once you pull the heads off you might as well replace all the gaskets that are right there.

The last thing you want is to replace just some of the gaskets there, put it all back together, and then need to tear it all back apart to replace a gasket you didn’t the first time. Once you have all the parts and supplies you need, go ahead and follow this step-by-step guide.

1. Drain the Oil and Coolant

You’re going to remove a lot of components to get to the head gasket, and the last thing you want when you’re working is to have a ton of oil or coolant spill out all over the engine when you take something off.

You’re going to need to replace the coolant and oil to finish the job anyway, so do yourself a favor and drain them both out in the beginning.

2. Disconnect the Battery

If this isn’t already one of your first steps for just about any job, you should make it one. Anytime you’re taking off sensors or working with any electrical components in your vehicle, you run the risk of shorting something out.

All it takes is a second of shorting out a sensor and you’ll need to replace it, driving up the overall cost of the repair. Simply disconnecting the battery before you start eliminates the risk entirely and only takes a minute or two.

3. Tear Down the Engine

All right, this is where things get a little more complicated for you. While we’d love to give you a step-by-step guide to what to remove and when it all comes down to what kind of vehicle you’re working on. You need to remove all the head gasket bolts, but there are going to be lots of components on top of them.

Take off everything you need to in order to reach the heads, and mark and tag the bolts so you can put them back where they belong. If you remove components with gaskets, you need to replace the gaskets when reinstalling the components.

Take your time here, it’s going to take a little bit of work to get to the heads. Finally, after you remove all the necessary head bolts and the components on top of them, gently pry the head up and remove it.

4. Inspect Components

As you’re taking off different components, do yourself a favor and inspect them for any possible damage. You’re taking the time to tear everything apart, you might as well fix any little things you might come across.

This will also ensure that you don’t put in all the work to replace the head gasket only to have a new problem when you put everything back together.

5. Replace All Gaskets

Once you have the head gaskets off, replace all the gaskets under there. Replace the gaskets around each channel and around the exterior of the head gasket itself. Your kit should have all these gaskets, so don’t leave any of the new gaskets in the pack!

6. Reinstall and Torque

Now that you finished replacing all the gaskets, it’s time to put everything back together. When you’re putting the engine back together ensure you follow all the torque specs and the tightening sequence.

You don’t want any leaks or problems at the end of the job and following the correct torquing procedures is the best way to ensure that won’t happen.

7. Replace Oil Filter

Before you put new oil in the engine, do yourself a favor and replace the oil filter. They only cost a few bucks and the one on your engine and coolant running through it. You already put in a ton of work and money, don’t skimp on this small part.

8. Fill Up Fluids

The last thing you need to do once you have everything back together is put new oil and coolant in the engine. Your engine can’t run without them, so don’t forget this crucial final step!

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Rickard Cefalk

Rickard is the owner of and a dedicated and avid do-it-yourselfer who has always enjoyed working on his own vehicles since childhood. He now devotes his time to sharing his expert knowledge of car maintenance and other car-related information through his website.

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