Oil and antifreeze mixture

Blend of oil and antifreeze in the expansion glass of the car

A breakdown that can affect us bring many head breakers is the mixture of oil and antifreeze . If when you go to check the levels of your car, we find a mixture of these two liquids in the expansion bottle, you can start to worry because, in principle, it is not a simple fault.

Engine has several conduits inside it. Some of these lines circulate the oil to grease the engine and others circulate the antifreeze, which takes care of its cooling . These liquids should not be mixed and, if they do, it means that something has broken. Usually the leak is in the cylinder head gasket or the oil cooler . Two very different faults, mainly because the first one is usually more expensive to repair.

How to know if they have been mixed

Expansion vessel

To easily recognize if the mix has occurred, you must open the cap on the expansion bottle . If you find a yellowish or brown viscous substance , there will be no doubt that oil has been put into the cooling system. However it is not always so. It only becomes a paste of that color when the leak is very abundant. In case you only mix a little, you will find oil stains floating on the antifreeze. So look closely.

Mix of oil and antifreeze in the expander cup of the color car

Oil level

The next check that is usually made is to look at the oil level . If you see that you have exceeded the maximum marked on the rod, without you having thrown more, it means that the antifreeze has entered the oil ducts. An even more serious problem than the opposite process (oil in the cooling system). Anyway, when you mix the two liquids usually invade both systems .

What has been broken

As we have told you, the problem is usually in the cylinder head gasket or in the oil cooler. Two breakdowns with a very large price difference, more by number of workshop hours than by the price of the parts.

Head gasket

This repair requires several hours and we will have to prepare the pocket. Lifting the cylinder head implies, at least, checking the cylinder head itself and putting a new gasket set , it being more than advisable to change the bolts as well. In the worst case, if the cylinder head is damaged, we must replace it with a new one, although it may be "only" necessary to plan it. Changing the stock for a new one is very expensive, so if it is not cracked and you just have to plan it, we can feel lucky.

Oil and antifreeze due to problem in cylinder head

Oil cooler

Another cheaper option is that has been mixed in the oil cooler . As its name suggests, it is responsible for cooling the oil by means of the antifreeze used to cool the engine. It has the shape of a small radiator in which both liquids enter.But if for whatever reason you want to ensure yourself what the problem is, there is a way to check if you have some knowledge of mechanics. It's about isolating the oil cooler from the car's cooling system . An operation consisting of:

  • emptying the oil and antifreeze from the car
  • remove the sleeves that carry the antifreeze to the cooler
  • splice to Close the cooling circuit without the cooler. Do not forget to cover the inlet and outlet of the cooler or at least join them by means of a sleeve so that nothing comes in.
  • fill the oil motor again and the cooling system with distilled water
  • and start the engine until it reaches the operating temperature to see if the oil rises again above the maximum level. If this does not happen, it means that it was the cooler that mixed both liquids.

Two important clarifications : first, each sleeve you put on should be fine adjusted with clamps and second, reach the cooler is not always easy, so if you have to remove parts to reach it, look carefully as was to leave them the same then.

Anyway, if you you find in this situation, the most advisable thing is to go to the workshop as soon as possible to verify the problem. If you do not, it can have very serious consequences for the engine.

If you want to know more about automotive mechanics and its maintenance is not miss the articles:

  • How to check an air filter
  • The intake manifold and the exhaust manifold
  • How to change the oil your car?
  • Remove the carbon from your car
  • Operation of the engine cooling system.
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