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How to Choose and Test Cooling Water for Diesel Genset

Dec. 13, 2018

Matters needing attention when adding cooling water and antifreeze to diesel generator sets


When the diesel engine is working, the water level in the radiator will gradually decrease due to the evaporation of the water. Therefore, the water level in the radiator should be checked before starting and when the starting time is long. If it is lower than the drain pipe, Replenish clean soft water. If it is hard water, it should be softened first.

How to Choose and Test Cooling Water for Diesel Genset.jpg


When the diesel engine is used under the environmental conditions below 0 °C, the cooling water should be prevented from freezing to avoid being freezing and cracking of the parts. Therefore, the cooling water should be drained whenever the diesel engine is finished running. For models with closed-loop cooling system, anti-freeze coolant with appropriate freezing point can be used according to the local minimum ambient temperature. Commonly used coolants include ethylene glycol plus water and alcohol, and glycerin plus water. The corresponding formula is shown in the table below for your reference.


Formulation of antifreeze coolant



Solidifying point/℃

Ethylene glycol




Unit of composition ratio 





Volume ratio 











Alcohol, glycerin antifreeze




Quality ratio











When using flammable antifreeze coolant, it is flammable due to ethylene glycol, alcohol and glycerin. Before using the antifreeze coolant, the diesel engine should clean the dirt in the cooling system to avoid new chemical deposits and affect the cooling effect. For diesel engines that use antifreeze coolant, it is not necessary to release the coolant after each stop, but it is necessary to periodically replenish and check the composition. Never use 100% antifreeze as a coolant.


If there is too much scale and dirt in the diesel engine cooling system, it can be cleaned with a cleaning solution. The cleaning solution can be prepared from water, soda (Na2CO3) and water glass (Na2SiO3) by adding 40 g of soda and 10 g of water glass per liter of water. When cleaning, the cleaning liquid is poured into the cooling water chamber of the diesel engine, and the running water reaches the outlet water temperature greater than 60 ° C, and the operation continues for about 2 hours to stop, and then the cleaning liquid is discharged. After the diesel engine is cooled, rinse it twice with clean fresh water, drain it and then pour it into the cooling water to start the operation, so that the outlet water temperature reaches 75 °C or more, stop the sewage, and finally fill in the new cooling water.


How to use the diesel cooling water test kit


For diesel engine cooling water, you must choose soft water instead of hard water. 40% antifreeze and 3~5% rust inhibitor (DCA4) can be added to the cooling water. The concentration of the additive must be checked every 500 hours to keep it within the correct range.


Number of antifreeze in winter


Ambient temperature

Cooling water%

Antifreeze (%

Above -10






















How to use the cooling water test kit

1. When the temperature of the cooling water in the diesel engine is (10-55) °C, unscrew the blockage to discharge the cooling water and fill the semi-plastic cup.


2. Dip the test paper into the collected water sample, stir the water sample, and after 3 to 5 seconds, remove the test paper and shake off the water drops on the paper.


3. Wait 45 seconds until the color of the test strip changes.


4. The test paper of the changed color is compared with the color list label on the storage bottle to calculate the value.


5. The color tone that has become yellowish green is compared with the green indication of the test paper storage bottle to determine the concentration. (The concentration display must be between 33% and 50% in the tonal range).


6. The brown color in the middle of the test strip and the pink color in the lower position represent the concentration of the rust preventive. The appropriate range is to satisfy the values of brown (vertical) and pink (horizontal), and is located in the range of 0.3 to 0.8 in the color list label on the test paper storage bottle. .


7. If it is lower than 0.3, a rust inhibitor (DCA4) should be added; if it is higher than 0.8, 50% of the cooling water should be poured out and fresh cooling water should be refilled. Then adjust to the appropriate concentration.


The coolant must generally be replaced every 6 months, otherwise lime and corrosive deposits will occur, affecting the diesel engine cooling system.


How to soften hard water into cooling water suitable for diesel generator sets


The cooling water used in the diesel generator set should be clean soft water. Soft water refers to water with little minerals, such as rain and snow. Most of the water is commonly used in river water, well water, etc. Before it is softened, it contains a lot of minerals in addition to sediment and other impurities. This water is usually hard water. After the salt water is heated in the cylinder, the mineral will form scale on the water jacket wall. The heat transfer capacity of scale is very poor, its thermal conductivity is 50 times lower than that of brass, and 20 to 30 times lower than that of cast iron. Therefore, the heat of the cylinder and the cylinder head cannot be smoothly transmitted to the cooling water, which easily causes the machine to overheat, even burns the lubricating oil, accelerates the wear of the components such as the cylinder and the piston connecting rod group, thereby reducing the power of the diesel engine. In addition, too much scale can not block the water pipe and the cylinder water channel, making the cooling water circulation difficult. Therefore, hard water is preferably softened before use. Common hard water softening methods are as follows:


1. Boil hard water

2. Grass ash softening


(1) The sifted ash is placed in a bag. Usually, the amount of ash in the cooling pool or water tank is 1 liter of water and 4 g of ash.


(2) Grass ash leaching method: Add one part of grass ash and nine parts by weight of water to the wooden barrel, stir several times, stir once every 20 minutes, and then use for 15 hours to be used. When hard water softens, the amount of leaching solution is: 4L leachate for 100L hard water.


3. Ammonium nitrate softening method: Ammonium nitrate and calcium bicarbonate in hard water react chemically to form ammonium hydrogencarbonate and calcium nitrate dissolved in water to soften hard water. Softening the hard water with ammonium nitrate also dissolves the formed scale.


Specific operation method: dissolve the ammonium nitrate crystal into an ammonium nitrate solution, and then add it to the cooling water, and add 3 to 4 grams of ammonium nitrate per kilogram of hard water. Generally, the diesel engine needs to be replaced with the same new cooling water for 4 to 5 days.


4. Caustic soda softening method: caustic soda reacts chemically with calcium bicarbonate in hard water to form water-soluble sodium carbonate and water-insoluble calcium carbonate to soften hard water. 6.6 g of caustic soda per 10 L of water.


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