Reduced thrust, difficult start and increased fuel consumption are the first signals that give combustion-engine Most often, these problems are caused by the formation of dense carbon deposits on the piston rings and cylinder walls, a process known as coking, which is inevitable when machinery is actively used, especially if fuel of questionable quality is used or oil change intervals are disrupted.
Ignoring the symptoms can lead to rings, the appearance of deep bullies on the cylinder mirror and, as a result, to expensive overhauls. Decoxing This is a preventive measure to restore compression and normalize the power unit without fully disassembling. In this article, we will discuss in detail the chemical and mechanical cleaning methods, as well as the nuances of the procedure for different types of motors.
Causes and consequences of the formation of nagar
The basis for solid sediment formation is incomplete combustion of the fuel-air mixture. Under ideal conditions, gasoline or diesel fuel burns completely, turning into carbon dioxide and water. However, in reality, especially when working at low speed or in warm-up mode, some hydrocarbons do not have time to oxidize and settle on hot surfaces as a form of water. smog.
Compounding the situation is the use of low-thermal-stability oils, where at high temperatures, the oil film on the cylinder walls burns out, leaving behind lacquer film and coke. Over time, these deposits accumulate in the grooves of piston rings, depriving them of mobility, the rings stop fitting tightly to the cylinder walls, causing gases to break into the crankcase and fall. compression.
The consequences of ignoring the problem are cumulative: first, the motor unit simply loses power, then it starts to smoke blue or black smoke. In advanced cases, there is a potassium ignition, when the engine continues to work after turning off the ignition due to red-hot carbon particles, which is a direct route to the burn of the valves and the destruction of the piston group.
Chemicals for removing coke
The modern chemical industry offers a wide range of liquids designed specifically to dissolve carbonaceous deposits, which are divided into soft (fuel or oil additives) and aggressive (fill directly into cylinders). For motor-blocks where access to the insides is limited, the second method, often called soft decoking or candle opening, is most effective.
The popular kerosene, acetone and special solvents are used to soften even old, sintered soda, turning it into a liquid substance that then burns out or is removed through the exhaust system. It is important to choose products that are safe for rubber seals and gums, because aggressive chemistry can damage. sealing.
⚠️ Warning: Aggressive chemicals can dissolve the oil film on the cylinder walls. After the procedure, be sure to replace the engine oil and filter, even if the replacement time has not yet come.
When choosing chemistry, you should pay attention to the specialization of the product. Some formulations are only for gasoline engines, others are universal. Briggs & Stratton or Honda It is better to use proven brands such as Lavr, Gzox or Hi-Gear, which ensure that there is no harm to catalysts (if any) and sensors.
Preparation of the motor unit for the procedure
You can't do a good job of decoding without the right technology. The first step is always to get the engine to the operating temperature. The heat gap between the parts is minimal when the heat is warmed up, so the chemistry is more efficient. Let the engine run for 5-10 minutes at medium speed.
Then the equipment must be silenced and access to the spark plugs. Depending on the design of the motor unit, you may need to remove the protective casing or air filter. Be careful when unscrewing the candles on the hot engine - use a candle key and protective gloves to avoid burns.
Before pouring the product, it is recommended to manually turn the crankshaft to set the pistons in the middle position, this will allow the liquid to cover the maximum area of the working surface of the cylinder and rings on all sides. If the pistons remain in the extreme positions, the top of the cylinder and the bottom of the piston may remain untreated.
☑️ Preparation for decoction
Technology of carrying out decoking DIY
The cleaning process depends on the method chosen, but the classical algorithm of actions remains unchanged: after preparation and warming up, a certain amount of cleaning liquid is poured into each cylinder through the candle hole (usually 20-50 ml, depending on the cylinder volume), then the candles are twisted back (or the holes are simply covered with rags) so that the vapors do not evaporate.
The engine is left alone for the time specified in the instructions for the chemical, usually taking from 30 minutes to several hours, it is recommended to periodically turn the crankshaft with a starter (with twisted candles) or manually so that the liquid penetrates deeper into the rings, this movement helps to "stir up" the deposited coke.
After exposure, the candles are twisted out, and the engine is scrolled by the starter several times to throw out the remaining dirt and liquid from the cylinders, then the candles are put in place, and the engine is started. The first minutes of operation will be accompanied by abundant smoke and clapping, which is normal, because dissolved carbon monoxide burns out.
Folk methods of decoxting
As a budget alternative to professional chemistry, a mixture of kerosene and acetone in a ratio of 1:1 or even pure acetone is often used. There is also a method using dimexide (pharmacy), which dissolves soda well, but requires extremely careful handling, since it can be aggressive to certain types of rubber and plastic, the use of such mixtures is justified only in the absence of special products at hand.
Comparison of engine cleaning methods
The choice of method of removing the coal depends on the condition of the engine and the owner's budget. Mechanical cleaning requires a complete disassembly of the engine, which guarantees the perfect result, but time consuming. Chemical decoking without disassembly is a compromise option that allows you to extend the life of the unit without complex repairs.
Below is a comparative table of the main methods used in a garage or workshop:
| Method | Efficiency | labour-intensiveness | Risk of damage |
|---|---|---|---|
| Chemical (no disassembly) | Medium/High | Low. | Low (if dosages are observed) |
| Mechanical (disassembly) | Maximum | High. | Medium (human factor) |
| Fuel supplements | Low (prevention) | Minimum | Missing. |
| steam-oil bath | High. | Medium | Average (temperature control) |
It is worth noting that mechanical cleaning It's often necessary if the rings are so buried that the chemistry can't release them, and in such cases, you have to remove the cylinder head and manually clean the pistons with brushes, but for regular maintenance, the chemical method is the optimal balance of price and result.
After the decoking and heating procedure is completed, allow the motor unit to cool naturally. Sharp cooling can lead to deformation of the HBC or the appearance of microcracks in the metal due to temperature changes.
Compression recovery and checking the result
The main indicator of successful decoking is compression recovery, which can be measured using a special device, a compressometer, which is screwed or inserted into the candle hole. Normal values for motor motors usually vary in the range of 6-9 atmospheres, depending on the degree of compression of a particular model.
If the compression hasn't grown after the procedure and the engine is still working or smoking, it's probably not just the dip that's causing the problem, it's probably already worn out, it's worn out, it's mechanically damaged, and then decoxing won't help, and you'll need to replace the piston group.
Also worth paying attention to the color of the exhaust. The transparent exhaust indicates normal combustion of the mixture. Black smoke indicates over-enrichment of the mixture or wear of the cylinder-piston group, and gray - a combustible of oil. If after decoking oil consumption decreased and the traction returned, the procedure can be considered successful.
Decoxing is not a cure-all, but a way to extend the life of the engine, and if the wear of parts exceeds the permissible limits, only repair or replacement of components will help.
⚠️ Warning: When working with an open fire or a hot engine while burning out residues of chemistry, always have a fire extinguisher on hand. solvent vapors are easily ignite and can flare up in the exhaust system.
Prevention of engine coking
To avoid the need for frequent decoding, it is important to follow the rules of operation of the motor unit. Use only high-quality fuel with the octane number recommended by the manufacturer. Low-octane gasoline burns more slowly and at higher temperatures, which contributes to the active formation of sodium.
Change engine oil regularly. Old oil loses its lubricating and cleaning properties, begins to coke and contaminate the engine. For motorblocks, it is better to use synthetic or semi-synthetic oils with a high index of thermal stability. Also monitor the condition of the air filter - the polluted filter disrupts the mixture, leading to work on the enriched mixture.
Periodically, let the engine work under high-speed loads. Long-term idling or gentle work contributes to the deposition of the coal. Short periods of full-power operation help the cylinders to "self-clean" through high temperature and gas flow rates.
Effects of ethanol in fuels
Modern gasoline often contains ethanol, which can be aggressive to some rubber and plastic in a carburetor, and is hygroscopic (absorbs water). The water in the tank leads to corrosion and combustion deterioration. Try not to store the equipment with a full tank of fuel for a long time (more than a month), especially in winter.
Can I use a cold engine to drive?
It is strongly recommended not to pour chemicals into the cold engine, the effect of the procedure will be minimal, since the reaction of dissolving the soda requires a high temperature, and most of the liquid simply flows into the crankcase, diluting the oil, instead of working in the cylinder.
How often should you do the decoding?
Preventive decoking is recommended once a season or after every 50-100 hours of operation. If the motor unit is used intensively and with heavy loads, the interval can be shortened.
Is the scaling dangerous for older engines?
For severely worn engines, aggressive chemistry can be dangerous. Dissolved soda, which previously sealed the gaps between the piston and the cylinder, can disappear, and the compression will fall even more, and there is also a risk that movable rings released from coke will begin to hang in worn grooves.
Should I change the oil after the oil is removed?
Yes, oil change is mandatory. Some of the cleaning fluid inevitably enters the crankcase, mixing with the lubricant, which reduces the viscosity and protective properties of the oil, and even if you've used soft products, replacing the filter and oil after the procedure is a must to keep the engine alive.
Will the engine be able to smoke if the engine is smoked?
If the smoke is caused by rings and the accumulation of sodium, then decoking will help eliminate the cause. If the smoke is due to wear of oil caps or production in cylinders (bullyers), chemical cleaning will only have a temporary effect or will not help at all.