Engine decarbonization is a popular term, which refers to the procedure for removing carbon deposits, primarily leading to the occurrence of piston rings. However, there are other issues that come up along the way. This article on Auto without a service station describes in detail the essence of decarbonization, the symptoms of a motor that needs it, as well as the main methods of implementation. A step-by-step instruction is written on how to decarbonization the engine without disassembly.

The essence and purpose of decarbonization

The main task of decoking the engine is to free the stuck piston rings. This happens for many reasons - due to overheating, oil starvation, low-quality engine oil, untimely replacement. When the engine is operated incorrectly, carbon deposits gradually form in the piston grooves, which among motorists is commonly called coke. Over time, it becomes so much that the rings are blocked in their grooves, that is, they lie.

Dead rings are idle rings. Compression can’t fit the cylinder, resulting in loss of compression. In a gasoline engine, the air-fuel mixture cannot compress normally and a lot of energy is lost from its combustion. In a diesel engine, it is even worse - due to poor compression, air is not compressed, in which the fuel injected by the nozzle should ignite. When the oil scraper rings lie down, they stop removing engine oil from the cylinder walls, and it enters the combustion chamber in large quantities.

It is not only piston rings that suffer from the so-called coke. The piston itself is also covered with soot, as a result of which the volume of the combustion chamber and the quality of mixing of the air-fuel mixture decrease. They also cover the valves and their seats, because of which the compression drops with all the ensuing consequences.

The purpose of decoking the engine is to remove all the carbon deposits described above and, first of all, to release the stuck piston rings. Along the way, the working side of the pistons, valves and their seats are cleaned. The essence of decoking the engine without disassembly is to dissolve this very deposit.

Signs of an engine in need of decarbonization

Blackened fresh oil is one of the signals
Blackened fresh oil is one of the signals

In no case should decarbonization be considered a mandatory procedure, which sooner or later every car owner will have to face. If the engine is operated correctly and serviced in a timely manner, then there will be no problems with soot in it until the resource is completely exhausted and overhauled. However, if the car was “tormented”, overheated, did not change the engine oil for a long time and neglected flushing at the same time, problems with soot are provided.

Soot on nozzles
Soot on nozzles

You should think about decoking if:

  1. There is a wild consumption of engine oil.
  2. Fuel consumption has increased abnormally.
  3. The machine constantly smokes gray or bluish smoke.
  4. Lost power.
  5. The engine began to start with difficulty when cold.
  6. Unstable idling.
  7. Fresh motor oil turns black quickly.

The first thing to do when these symptoms appear is to look at the condition of the spark plugs or injectors. If they are full of oily soot, then there is a high probability that the rings are stuck. Since soot can also indicate a too rich fuel mixture, it is additionally worth measuring the compression. If it is inadequately low, the problem is in the rings or valves.

Coking of rings or valves is not the only cause of low compression. Perhaps the valves are not ground in, and the rings are simply worn out or completely destroyed. In such cases, after decoking, as a rule, the motor behaves even worse than before it.

Decarbonizing methods

Stuck piston rings
Stuck piston rings

There are 5 ways engine carbon cleaning:

  1. Mechanically, with disassembly. On the one hand, this is the most reliable and effective way, but complicated and not always mandatory, on the other. It consists in the fact that carbon deposits are removed from engine parts after partial disassembly. The big advantage of this method is that it is possible to visually assess the condition of the piston rings and find out the exact cause of the reduction in compression.
  2. Fuel additives. Special products are added to gasoline or diesel fuel that help dissolve carbon deposits on valves, their seats, pistons and rings. Such additives do not act quickly, and sometimes they cannot cope with stuck rings at all. Usually, the procedure is delayed by 200-400 km. If no improvement is observed during this time, then either the problem is not soot, or the selected additive cannot dissolve it.
  3. Additives in motor oil. The worst way to decarbonization, since the substance poured into the crankcase will “get” only to the oil scraper rings. When they decarbonization, the additive will not get anywhere else, and soot on the pistons and valves will remain.
  4. Water. Pretty ambitious, but it must be admitted, an effective method of decoking the engine without disassembly. It consists in the fact that finely sprayed water is supplied in small doses to the intake manifold when the engine is running. At the same time, coughs, twitches and stalls. But after several attempts, the soot, nevertheless, can succumb and be dissolved by the steam formed as a result of the evaporation of water.
  5. Special means without disassembly. The essence of the method lies in the fact that a dissolving aggressive substance is poured into the combustion chambers through the holes for candles or nozzles.

Since the last of the listed decarbonization methods is the most popular, we will dwell on it in more detail.

Engine decoking without disassembly

Valves before and after
Valves before and after

All that is needed to decarbonize the engine in this way is a special tool from an automotive store or any solvent for paintwork materials, as well as a medical syringe with a dropper tube. The procedure is as follows:

  1. If the engine starts, start it and warm it up to operating temperature at idle.
  2. Remove spark plugs or injectors.
  3. Examine them as described above.
  4. Jack up one of the drive wheels.
  5. Engage direct gear (highest) at the checkpoint.
  6. By rotating the wheel, try to set all the pistons to the middle position between TDC and BDC, controlling it with a long screwdriver inserted into the holes for candles or nozzles.
  7. If the engine is a single cylinder, set the piston to TDC between the exhaust and intake strokes.
  8. Using a syringe with a tube, pour 30 ml of a special agent or solvent into all cylinders.
  9. Now wiggle the hung wheel a little in both directions, but do not turn it more than 20 degrees.
  10. Cover the holes for candles or nozzles with rags, or wrap them so that dust does not get inside.
  11. Leave the engine like this for a couple of hours.
  12. Open the holes for the candles or nozzles.
  13. Cover them with a clean cloth.
  14. Rotate the crankshaft several times with a suspended wheel or starter.
  15. Screw in the candles (nozzles), remove the jack and try to start the engine.

Most likely, the engine will not start on the first try. If it does not respond after several starts, then the reason is not the occurrence of the rings. If the engine is started, it will initially work unstably, and dense black smoke and a pungent smell will come out of the exhaust. After a few seconds, if the decarbonization was successful and gave a result, the motor will work in normal mode.

Such smoke after decarbonization is the norm
Such smoke after decarbonization is the norm

Immediately after decarbonization the engine in the described way, it should not be subjected to serious loads. Remember that most of what you poured into the cylinders ended up in engine oil. Therefore, after making sure that the engine is running normally, change the oil to fresh and, if necessary, flush, as described in this article on Auto without a service station.

VIDEO: engine decarbonization


Decarbonization is not a myth
Decarbonization is not a myth

Engine decarbonization without disassembly is not a myth, but a completely effective procedure that allows you to solve the problem with stuck rings and soot in the combustion chamber. To understand that it was successful, just measure the compression. If the rings were really stuck, and now they are not, according to the readings of the compression meter, this will definitely be visible.