What to do if the antifreeze gets into the engine oil

Antifreeze in the oil: Possible causes and troubleshooting

The engine of a car involves a lubricating and cooling system. These are two indispensable components of any internal combustion engine. In these systems, different fluids are used, which in the normal operation of the engine should not overlap with each other. However, in the case of a failure of any element, oil in the antifreeze appears. The causes may be different. Well, let’s consider this problem in detail.


If the antifreeze gets into the oil, how do you determine this? There are several signs that you should pay attention to:

  • Coolant level. On a serviceable engine, it should not change during operation. However, if the level decreases even slightly, it may indicate that the antifreeze is getting into the engine oil.
  • Exhaust. The exhaust becomes whiter and thicker. When the engine is running, a specific vapor is formed. But it should be understood that this phenomenon is considered normal in severe frost. However, if the temperature outside the window is plus, it is a clear sign that the antifreeze gets into the oil.
  • Candles. The electrodes of the spark plugs will be flooded with the antifreeze and emit a characteristic odor.
  • Oil. It in the case of antifreeze ingestion changes its hue, as well as the structure. Usually the oil becomes almost white.
  • Emulsion on the oil filler neck. It may resemble a thick “mayonnaise”.

About white flecks on the spark plugs

If white fouling has formed on the spark plugs, the reasons can be different. First of all, it indicates a problem with the quality of the fuel. But if it is a rough white fouling on the spark plugs, the reasons are in the overheating of the motor. Also such fouling is formed if:

  • The spark plug is not suitable for the given engine (in terms of gauge number or other parameters).
  • The intake manifold is leaky. This is where the air will be drawn in from outside.
  • Poor ignition calibration.
  • There are problems with the cooling system (e.g. faulty radiator).

Why does the coolant get into the oil?

Experts distinguish several reasons for this phenomenon:

  • Deformation of the gasket that separates the block and the cylinder head. This is the answer to the question of where the antifreeze goes, if it does not leak anywhere. There are separate channels for the coolant in the internal combustion engine. But their isolation is incomplete due to tears at the joint between the block and the cylinder head. A gasket is installed to provide a seal. This also prevents oil leakage. But if the cylinder-head gasket is punctured (symptom – emulsion in oil), the antifreeze will penetrate into the lubrication system. The element is punctured due to a blowout. Also if the cylinder-head gasket is punctured, the symptoms will be as follows: coolant level drop and characteristic white smoke from the exhaust.
  • Defects in the cylinder head. The key here is not the cylinder head itself, but the area that is adjacent to the cylinder block. If there is a deformation in one of the areas, the tightness of the gasket will deteriorate. Even if the gasket is not damaged, insufficient sealing will cause the antifreeze to get into the oil. This problem is complicated by the fact that you will not be able to notice it at once. Where does the antifreeze go if it is not leaking anywhere? It mixes in small volumes with oil. And it is possible to detect a head deformation only after defektovki. For this purpose a specialized tool is needed. The head is placed on the rib and the flatness is determined with a metal ruler. If a defect is detected, the head is ground.
  • Defects of the block body. This applies to the sections of the channels, where the coolant circulates. This problem is the most serious, as the engine has to be removed from the car.

What to do if the coolant got into the oil?

So, having determined the cause of the problem, you can proceed to repair. The easiest option is to replace the head gasket. But this is done only in the case of its blowout. To do this, remove the cylinder-head, clean the place of the old gasket, put a new one and tighten the bolts with the appropriate torque. As practice shows, no more antifreeze gets into the oil. In this case, the repair costs will be minimal.

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But the most difficult stage in the work is the removal and subsequent installation of the head block. In this case, a torque wrench will be required. Bolts should be tightened in accordance with the scheme (usually crosswise). Tightening torque is individual for each car.

It will be useful to inspect the head. If there are surface imperfections, grinding is necessary. But it is performed only with the specialized equipment. Here you can not do without a wizard. If the cylinder head is “warped” (e.g., from severe overheating), the grinding can be of no help. In such a situation only the installation of a new head is needed. The same concerns the block. If it has cracks, you need to replace the block.

How is the gasket changed?

Let’s consider the replacement procedure on the example of the car VAZ-2109. To do this, we need:

  • Remove the body of the air filter.
  • Disconnect all fuel hoses and power wires.
  • Drain the coolant.
  • Unscrew manifold.
  • Disconnect the high-voltage wires.

This way, we free the head from everything unnecessary so that nothing interferes with the removal. To unscrew the head itself you need a strong screwdriver and an allen key. It is necessary to unscrew a total of 10 bolts. The last ones are taken out together with the washers. Then the head is carefully lifted up. It is important not to warp it. The gasket itself can stay on the head or stick to the block. You can remove it with your hands or pick it up with a minus screwdriver. Inspect the cylinder head surface for corrosion. If there is rust, it is necessary to perform milling and grinding. If all is well, it is necessary to remove traces of the old gasket. Having cleaned the surface of its remains, degrease the place.

What next?

Install the new gasket. When installing, you need to pay attention to ensure that the gasket aligns with the guides that are on the corners of the block itself. Next, the block head is mounted. It is important not to displace the gasket. Then tighten the bolts with a torque wrench in three steps:

  1. 20-25 Nm.
  2. 70-85 Nm.
  3. 120 Nm. After the bolts are tightened to a torque of 140 Nm.

The next step is to assemble all the attachments, and the car will be ready for operation. At the first startup, you need to warm up the engine to working temperatures, and then perform the first trip.

Flushing Features

If antifreeze gets into the oil, you need to understand that the engine will need to flush the systems. The first thing to do is to flush the circle through which the coolant moves. To do this, you need a special solution, which can be found in auto stores. The product is poured into the expansion tank, and the engine is started for 10 minutes. When the fan turns on, you can complete the flushing.

After that the old tosol is drained off. Prepare a container of not less than five liters in volume beforehand. Next you need to remove the oil cooler (if any in the car). On different cars it is removed in different ways. After dismantling it is necessary to thoroughly clean it and install new seals.

Next removes the expansion tank. It must be washed. Distilled water is poured into the motor, and the engine is started. After the engine has warmed up, it is necessary to turn on the cabin air blower. The heater should work for 10 minutes. Next, the engine is turned off. Drain the fluid. After this you can already pour in fresh antifreeze. Sometimes an air plug is formed in the system. To remove it, you need to open the cap of an expansion tank and squeeze the socket of the coolant system.

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Pay attention that flushing of the system is made after installation of a new gasket. At the same time the oil is also changed.

Consequences of driving with a punctured gasket

It is prohibited to operate the car, where the antifreeze gets into the oil. What is the cause? The liquid itself, despite its toxicity, does not harm the engine. But the danger is the ethylene glycol, which is contained in the coolant. If it mixes with oil, the result is the formation of abrasive particles. Because of this, there is a risk of scuffing.

What happens when the antifreeze enters the cylinder block? It then interacts with the oil and deposits form in the form of an emulsion. This leads to a reduction in the diameter of the channels. Lubricant and antifreeze are not able to circulate properly. As a result, the engine runs with insufficient oil pressure and overheats. The oil filter is also contaminated considerably.

The oil itself, diluted with coolant, loses its lubricating and protective properties. It reduces the service life of an internal combustion engine, and may lead to high repair costs.

Summing up

So, we have found out why the antifreeze gets into the oil. As practice has shown, this problem can be identified by the car owner in time. The main signs are a characteristic white exhaust and a drop in the level of antifreeze in the tank. If the fluid penetrates into the oil, the latter changes its structure. This is determined by the dipstick. In addition, suspicions may be supported by a wet electrode on the candles and the characteristic sweet smell of the toluene on them. We have considered the causes of antifreeze in the oil. You should not further operate such a car. Such an engine easily overheats. In addition, it will run with bad oil, which has lost all its positive properties. The cost of repair will depend on the essence of the problem. It can be a gasket, a head or a block. In the latter case, the cost of restoring the engine will be the most significant.

Antifreeze in the oil

Antifreeze in the engine oil can be due to different reasons – failure of the cylinder head gasket, damage to the cylinder head plane, damage to the heat exchanger and so on. However, in any case, the result of the fact that the antifreeze went into the oil will be very unpleasant consequences, consisting in the fact that the normal process of lubrication of individual engine parts with all the ensuing consequences will be disrupted.

Similarly, if oil penetrates into the antifreeze, the function of the engine cooling system will be impaired. Accordingly, if the above faults are detected, diagnosis and repair work should be carried out as soon as possible in order to minimize their negative effects and prevent costly repairs.

Antifreeze in oil

How to determine the antifreeze in the oil

Many, especially beginners, car enthusiasts are interested in the question of how to know that the antifreeze got into the oil system of the engine of the car. In fact, there are a number of typical signs by the presence of which you can judge the occurrence of this malfunction. Among them:

  • On the neck under the cap, there appears an emulsion of oil and antifreeze directly, usually white or yellowish in color, similar in appearance to cream (sour cream, mayonnaise). Correspondingly, the more antifreeze or fuel oil has leaked into oil system – the more such mixture will be in its composition. It is not difficult to check emulsion presence in an engine, just look at the engine oil condition on the dipstick. The same emulsion will be on the oil filler neck, you should only open the cap.
  • Coolant level drop . This sign is indirect, as antifreeze may leak from the system not into oil, but just into the underhood space. Therefore, in this case, it is necessary to carry out additional diagnostics.
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  • Engine overheating . This sign is also indirect, as it can also be caused by other problems. However, if there is mixing of antifreeze and oil, respectively, the cooling and lubrication systems will stop working normally, which will lead to rapid overheating of the engine, especially when it works at significant loads (speeds).
  • The presence of oil in the antifreeze . As a rule, in case of depressurization of one (or both) systems mutual mixing of these process liquids occurs. At that the antifreeze turns black and starts to smell of burning oil, and the cooling system is not working properly. You can see the condition of the antifreeze by opening the cap of the cooling system expansion tank.
  • Decline in engine power . This factor is a logical result of the deterioration of the cooling and lubrication systems. Often the engine “trots”. It is necessary to perform additional diagnostics, since the power loss may be caused by other problems.
  • White smoke from the exhaust pipe . This is relevant for both gasoline and diesel engines, but the reasons for this phenomenon are different in the first and in the second cases. If there is white smoke coming out of the exhaust system, then there is antifreeze in the engine components. For gasoline engines, the coolant goes into the cylinders, and for diesel engines, it goes into the manifold.
  • The spark plugs will have a light tint (the color of the burned antifreeze). True, this is only a circumstantial sign, you will need to consider a number of other causes.
  • Air bubbles in the expansion tank of the cooling system. You may see them through a transparent tank casing or by opening the lid (at high engine speeds). The higher they are, the more air will flow out of the system. This sign directly indicates a leak in the system.
  • Coolant leaks from under the cylinder-head gasket to the body of the block itself. Regardless of their color, it is necessary to check the condition of engine oil and antifreeze in the engine for mixing with each other.

If the car owner has experienced one or more of the above signs, it makes sense to check the condition of the engine oil, coolant, as well as perform additional diagnostics of individual engine parts, which will be discussed below.

Causes of antifreeze in the oil

There are a number of typical malfunctions that cause engine oil and coolant to mix in the internal combustion engine. Among them:

  • Burnout of the cylinder-head gasket . According to statistics, this cause is, firstly, the most common, and secondly, the easiest to fix. Gasket burnout can be caused by different factors, in particular: engine overheating, which “leads the head”, improperly chosen tightening torque of fixing bolts, natural aging of the material from which the gasket is made. Elimination of the described failure is possible to do to a car owner himself if he has appropriate tools. As for the financial costs, you will only have to spend money for a new gasket.
  • Disturbance of the cylinder-head geometry. Another popular name is “hung head”. More often this malfunction is the result of significant engine overheating, and it is more typical for small engines (for example, for town cars).
  • Failure of the heat exchanger (oil cooler) and/or its gasket.
  • Damage to the cylinder block . Occasionally (usually as a result of damage or defect) there are microcracks on the cylinder liners, which leads to mixing of oil and antifreeze. Here you can also note such a phenomenon as corrosion of the cylinder liners.
  • Incorrect connection of the cooling system line to the throttle. This is quite a rare cause, but it rarely occurs in used cars, whose past owners or craftsmen incorrectly connected the above-mentioned cooling system line connectors. At that, the antifreeze goes straight into the engine oil, and from there – into the exhaust system (manifold and further).

For clarity, the above causes and brief information about methods of their elimination are summarized in the table.

Schematic of a simple voltage regulator with LM317
Cause Methods of elimination of breakage
Burnout of the cylinder-head gasket Replacement of the punctured gasket with a new one. It is important to observe both the tightening torque value and bolt tightening sequence.
Alteration of cylinder-head geometry. Crimping, milling, grinding of the cylinder head. To be performed in specialized workshops. Check of its tightness.
Failure of heat exchanger and/or its gasket Gasket replacement, heat exchanger repair or replacement.
Damage to the cylinder block Repair of block in service conditions or replacement of block for a new one.
Corrosion of liners. Boring or replacement of the liners for new ones.
Improper connection of cooling system. Revision of wiring diagram. The problem is often actual for the cars, bought “from hand”.

It is interesting that many novice car enthusiasts confuse a little frozen oil during the frost and the antifreeze emulsion itself. It is important to understand that when the car is idle for a long time in winter at significant frosts, the oil thickens and may take on a yellowish tint. Therefore, you need to perform additional diagnostics when the engine is warmed up, so as to find out what the motorist is dealing with – frozen oil or emulsion.

Antifreeze in oil consequences

If you do not pay proper attention and do not perform timely repair of the car engine, the reasons why the antifreeze gets into the oil, can not only significantly reduce the characteristics of the engine, but also lead to difficult and expensive repairs. Specifically, this is due to the following factors:

  • Reduced efficiency of the lubrication and cooling systems. Thus, if there is coolant in the oil, the efficiency of lubrication will drastically decrease with all the ensuing consequences. That is, it will lead to excessive wear and tear of the rubbing parts of the engine (which is designed to protect the oil). On the other hand, antifreeze can also mix with oil. This will lead to two consequences. The first is that the coolant will also lose its performance characteristics (reduced heat capacity and its boiling point). The second is a reduction in the overall level of antifreeze in the cooling system, which itself reduces the effectiveness of its operation.
  • If there is a deformation of the cylinder head, it is possible that there are problems with pistons and rings. In particular, the piston body (several pistons) may get scuffed (due to overheating and changes in geometry). As for the rings, the compression and wear rings can also become damaged (ring lodging).
  • General decrease in engine efficiency. This is expressed in the loss of power, unstable operation of the engine, it can “sneeze” and “thrash”. In any case, it is not desirable to operate the car in such a condition, as it is not only harmful for the engine, but also unsafe from the point of view of driving on the road.

Many motorists are interested in the question of whether you can use to drive a car when the antifreeze is in oil? Ideally, the answer is simple – you can’t! But in practice, everything depends on the amount of antifreeze in the oil, availability of a car repair shop, and the general condition of the engine and the car as a whole. So, if the mixing is insignificant, you can drive the car to a garage or service station, where you can perform direct repair work. However, in the long run to use the car is definitely not! It can lead to very complicated and expensive repairs.

What to do if there is antifreeze in the oil

What actions to take if the antifreeze mixed with engine oil? The answer to this question depends on the cause that caused this malfunction. Let’s list the actions in the same order in which the above causes were listed above.

  • Failure of the cylinder-head gasket . In this case, it is necessary to replace the gasket itself. To do this, it is necessary to dismantle the cylinder head. During installation, it is important to be careful to accurately place the gasket in its seating position. The second important nuance is that it is very desirable to use a torque wrench when tightening the mounting bolts. They should not be tightened by eye as there is a high risk of exceeding the tightening torque which will damage the gasket and cause premature failure. For clamping torque values and bolt tightening sequences, refer to the technical documentation in the model-specific repair manual.
  • Disturbance of the geometry of the cylinder head. In particular, as a result of overheating or other mechanical damage, the cylinder head can occasionally “twist”, that is, the lower plane of the cylinder head becomes deformed. The solution to this problem is to grind the cylinder head on special machines, in particular, press and/or mill (grind). This should only be done in specialized workshops. After the repair work it is obligatory to check its tightness (presence of cracks).
  • Damage to the heat exchanger and/or its gasket. Most often it is the gasket that fails due to its natural wear and tear. The only way out in this case will be the replacement of this element. If it is the heat exchanger that is damaged, an attempt can be made to repair it (solder it), but that is not always possible. Accordingly, if it can not be repaired – it should be replaced by a new one.
  • Incorrect connection of the cooling system line. In this case it makes sense to check the correctness of connection of pipes, as well as gaskets (in particular, the manifold gasket).
  • Damage to the cylinder block . This is quite a complicated case, and to fix the fault it is necessary to dismantle the block. Repair work is carried out at an auto shop, where the block is bored out and new liners are installed in it. In the most complicated case, the entire cylinder block is replaced.
  • Foreign Leaks . In some cases, there are antifreeze leaks on the lines and/or at various connections. For example, on the temperature sensor (in particular, it is relevant for some models of Opel, on the pipe fluid supply to the heater). It is better to diagnose such leaks, when the engine is working at high revs, because in these conditions, the antifreeze is flowing with overpressure and it is easier to spot the leak.
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Regardless of the reason why the antifreeze got into the oil (or vice versa), after eliminating the causes and performing appropriate repairs, it is necessary to change the oil in the engine, as well as to replace the coolant. And before that, perform a flush of the cooling system and engine.

How to flush the engine when the antifreeze got into the oil

Engine flushing should begin with the fact that remove the old oil, which has some antifreeze in it. Then instead pour a special flushing oil. Different manufacturers have their own such compositions, so there is no point in advertising them. Or simply take a few canisters of the cheapest engine oil (still have to drain it after 100 km), you can also take the most accessible oil filter. So change oil a few times and then already pour the new oil necessary for the engine, and do not forget to put and a new good oil filter.

Often, when flushing the oil system from the emulsion use special oil system flushes or even diesel fuel (it’s great with condensed oil and liquid). But it’s still worth using an oil flush after such remedies.


Mixing of antifreeze and engine oil leads to significant negative consequences for the engine, especially in the long term. Therefore, if you identify the specified phenomenon, it is necessary to find out the cause as soon as possible and perform appropriate repair work. The most common cause of mixing of antifreeze and oil is a burned cylinder-head gasket. It is quite possible to change it by yourself. For more complex repairs, it is advisable to seek help from specialized repair shops.

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