Ⅰ.How to Maintain an Engine Cooling System?
Cooling System Impurities
After long time running, the cooling system may be affected by many types of dirt formed inside it. The type of dirt varies according to use and maintenance conditions of the cooling system. For example, as most engineering vehicles usually use water, the dirt formed inside the cooling system is mainly incrustation. However, for vehicles which always use antifreeze, the main impurity formed inside the cooling system may be gel-based dirt.

Other types of impurities inside the cooling system include: ① degraded anticorrosive agents, oxidized ethylene or propylene glycol ② heavy metals ③ hard water impurities ④ physical impurities ⑤ electrolyte

Major Faults of the Engine Cooling System
1. The water temperature of the engine is too high
2. The water temperature of the engine is too low
3. Cooling system leak

There are many reasons for engine overheating. The most common one is that the impurities formed inside the cooling system, like incrustation scale and gel-based dirt, block the waterway and thus affect the cooling effect.

Cooling system leak usually refers to the leak occurs in the water tank, water pipe and cylinder head gasket.

Solutions
1. Solution to High Temperature Problem
Cooling system cleaning agent together with special equipment can help solve engine overheating problem caused by dirt accumulation.
(1) How to choose the cleaning agent?
① Acidic cleaning agent is ideal for most sediments
② If the gel is not hard, you can also use alkaline or non-corrosive cleaning agent, in addition to acidic cleaning agent
③ Removing oily impurities requires acidic cleaning agent.
(2) Handling Method
Connect the special equipment to the vehicle, and put the cleaning agent to the engine cooling system. After it works under the normal operating temperature for 30 minutes, replace the old antifreeze through the equipment.
2. Solution to Cooling System Leak
(1) Leak Analysis
Water tank leak is mainly in the form of granule and strip. Water pipe leak is a problem usually resulting from crazing and aging, in addition to damages.
(2) Handling Method
By using plugging agents, water tank leak problem can be completely solved. The plugging agent, a chemical substance similar to a bulking agent, is capable of plugging all leaky parts.

Ⅱ Loader Hydraulic Torque Converter Oil Temperature Analysis
Ultra high oil temperature of a loader torque converter may cause many problems, such as oxidizing oil, reducing viscosity, decreasing transmission and lubrication functions, accelerating leak and parts abrasion, etc.

There are many different reasons that can cause high oil temperature of a torque converter, typically: unqualified hydraulic transmission oil, blocked filter, faulty rotary oil seal, loose connecting bolts, and cooling system fault.

How to Prevent Ultra High Oil Temperature of a Loader Torque Converter?
1. Select and Use the Right Hydraulic Transmission Oil
Choose the hydraulic transmission oil according to the temperature characteristics of the actual construction season. In addition, the oil should be oxidation resista nt, with certain viscosity.
2. Pay Attention to Maintenance
Keep the filter screen unblocked. Regularly check the oil filter if the wheel loader is equipped with it. The output shaft seals of the front and rear axles should also be inspected so as to prevent oil leak. Additionally, regular checks of the engine cooling water quantity and tensioning of fan belt are required to ensure there is enough cooling water and air.
3. Give Much Attention to Degree of Parts Wear and Assembly Quality
a. Keep the variable speed pump operating at peak performance. If the temperature of the pump is much higher than that of the tank, then an overhaul is required. The clearance between the pump cover and two gear faces should be 0.150～0.200mm, and the maximum width difference of a pair of gears should be less than 30mm. There should be no obvious scratches and grooves on the parts surface. The gears must be assembled in pairs and run flexibly.
b. During transmission overhaul, please focus on checking friction plate. There should be no spalling, cracks, debris or dust, and the friction plate and the steel sheet must be bonded firmly.
c.Maintain proper fit clearance of the speed change valve. If the clearance is too large, the pressure oil may be squeezed from the gap, which may cause throttle loss, resulting in high oil temperature. In addition, the pressure of the speed change valve should be properly adjusted.
d. After installation of the torque converter, all rotating parts should be able to rotate freely. Rotate the turbine set by hand, the first stage turbine blade and the second turbine blade should rotate flexibly and freely without clamping stagnation. Additionally, oil seals and seal rings should be damage free. Also, bearing failure must be eliminated. Furthermore, maintain normal oil pressure at the inlet and outlet of the torque converter
e. Avoid long-term overloaded operations.

Ⅲ Excavator Battery Maintenance
(1) Maintain a High Electrolyte Level
According to operating requirements, the electrolyte level should be 10-15mm higher than pole plate. In order to check this, you can insert a 150mm long glass tube (inner diameter: 4～6mm) vertically into the filling opening until it is in contact with top edge of the pole plate, then press the upper opening of the glass tube with your index finger and take the tube out with your thumb and ring finger. The electrolyte height in the glass tube is the exact height you need. If this height is less than 10mm, you'd better add a certain amount of distilled water timely. Please don't add any liquid like spring water, river water and tap water, as well as dilute sulphuric acid.
(2) Clean the Yellow-White Pasty Mass off the Battery Shell
The yellow-white pasty mass on the battery shell is caused due to electrochemical corrosion of electrode pole around which the sulfuric acid is splashed. The white mass is lead sulfate, and the yellow mass is ferric sulfate. The strong corrosiveness and great electric resistance may result in poor conductivity of the battery. To avoid this, you can use cotton yarn (which has been immersed in alkaline water or soda water) to clean off the splashed electrolyte. If there is any oxide in the gap between the pole and the conductor joint, please scrape it off.
(3)Periodic Boost Charge

Generally, the storage battery should be charged within 24 hours if it is flat; for unused machines, 1 time boost charge of their battery is required every month; 1 time boost charge of the battery which is in use is required every two month. (4) Regularly Inspect the Density of Electrolyte
Electrolyte density should be in accordance with the specific season and other conditions. For example, the density of electrolyte is relatively higher in winter.

Ⅳ Hydraulic Cylinder Maintenance
During the maintenance of engineering vehicles, we usually detect that there are some cellular cavities inside the hydraulic cylinder or at the surface of piston, piston rod. These cavities are caused by cavitation corrosion. Hydraulic cylinder cavitation could lead to burning of bearing rings and seal rings, and finally result in cylinder leak. In addition, cavitation, coupled with other types of corrosion, will greatly accelerate the corrosion of main hydraulic cylinder parts, thus significantly affecting the operation of the engineering vehicles like road rollers, loaders, and excavators.
1. What Causes Cavitation?
(1) Analysis of Cavitation
Cavitation is the formation of vapor bubbles of a liquid in a region where the pressure of the liquid falls below its vapor pressure. When the cavitation bubbles collapse, they force energetic liquid into very small volumes, thus creating spots of high temperature and emitting shock waves. The highly localized collapses can produce great wear on components of hydraulic cylinders.
(2) Cavitation Caused by Unqualified Hydraulic Oil
High quality hydraulic oil can effectively prevent cavitation. Bubbles can be easily formed in oil with poor antifoaming ability, thereby resulting in cavitation. In addition, if the frequency of oil pressure change is too high, air bubble formation and collapse can also be largely accelerated. Moreover, overheated oil will also increase the possibility of cavitation.
(3) Cavitation Due to Improper Manufacture and Maintenance
In the assembly or maintenance, air in hydraulic system is not discharged, which could cause cavitation under high temperature, high pressure conditions.
(4) Cavitation Resulting from Poor Quality Coolant
The coolant which contains corrosive medium like acid radical cation and oxidant is liable to chemical, electrochemical corrosion, thereby accelerating the speed of cavitation.

2. How to Prevent Cavitation?
Although there are many factors could cause cavitation, cavitation can also be avoided if we take effective measures to prevent it.
(1) Use High Quality Hydraulic Oil
Choose high quality hydraulic oil according to the related oil standard, because qualified oil can effectively prevent the formation of air bubble. Keep the hydraulic system as clean as possible, and regularly inspect the oil quality, oil level and oil color. Whenever water bubbles or foams occur in the hydraulic oil, please work to find the air source and then eliminate it.
(2) Prevent the Oil Temperature from Being too High so as to Reduce Hydraulic Shock
Reasonable design of the cooling system is key to maintaining normal temperature of hydraulic oil. In addition, smoothly operate hydraulic joystick, distribution valve and thrust lever, in order to minimize hydraulic oil's impact on the hydraulic components. Furthermore, timely maintain the cooling system so as to keep its temperature within certain boundaries, thus reducing the energy caused by the collapse of air bubbles.
(3) Maintain the Normal Clearance between Joint Surfaces of Hydraulic Components
When manufacture or repair main components of the hydraulic cylinder (like cylinder block, piston rod), please assemble them according to the lower tolerance limit of mounting dimensions, which can greatly reduce cavitation. If cavitation occurs in hydraulic components, utilize metallographic sandpaper polishing technique to remove cavitation pitting and surface carbon deposit.
(4) Pay Attention to Air Discharge during Maintenance
After maintenance, the hydraulic system should be operated for a while so that the hydraulic oil in the system can fully circulate. If necessary, disassemble the oil inlet pipe or return pipe so as to let the oil spill out of it, thus achieving air discharge of single cylinder.

Ⅴ Holes Shouldn't Be Blocked
Some "holes" in the construction machinery shouldn't be blocked, for example:
(1) Pump spill hole and drainage hole. The pump shaft is designed with a spill hole which can detect whether there is a leak in the pump and discharge the water leaked from the pump through it. If this hole is blocked, then the water leaked will enter the pump bearing to affect lubrication, resulting in damage to bearing and pump shaft. When the drainage pump is not operating, the drainage hole can be used to drain the retained water out of the shell. If this hole is blocked, the cooling water left in the pump will damage the water seal.
(2) The oil drain hole in the diesel oil transfer pump can directly drain off the leaked diesel oil from the pump. When this hole is blocked, the diesel oil left in the transfer pump will enter the oil pan of the injection pump to dilute lubricating oil, causing oil deterioration.
(3) The diesel engine is difficult to start if the 2mm conical nozzle in the cylinder head is obstructed.
(4) Once the oil return hole of the diesel engine injector is blocked, redundant diesel oil can not return to the fuel tank. This may cause the pressure in the oil return duct and injector increases, and consequently, change oil injection time.
(5) The vent hole in the fuel tank cap is used to prevent the formation of a vacuum as the oil level decreases, thus ensuring the normal oil supply.
(6) The vent hole in the oil filter cap can discharge waste gas out of the crankcase. The blockage of this hole will lead to oil leakage and oxidation deterioration.
(7) The diesel engine lubricating hole, through which the rocker arm, rocker shaft and valve push rod are lubricated, will significantly accelerate the wear of mechanical parts if it is obstructed.
(8) The dust discharge hole in the air filter can discharge dust particles. If this hole is blocked, the dust may enter into the next filtration device or even the cylinder, thereby accelerating mechanical parts wear.
(9) There are many oil return holes in the piston ring groove of the diesel engine, through which the excess oil scraped off cylinder walls can flow back into the crankcase. Blockage of these holes will make a large amount of oil enter into the combustion chamber and then cause oil burning.
(10) The drainage holes in the engine oil cooler and water radiator are intended to drain the cooling water out of each part. If these holes are blocked, especially in winter, the cooling water will freeze and thus damage the oil cooler and water radiator.
(11) The vent hole in the auxiliary water radiator cap of diesel engine. The formation of pressure difference between the main radiator and auxiliary radiator will be influenced if this hole is blocked, which could hinder the cooling liquid in the auxiliary radiator from flowing back into the main radiator, thus greatly affecting the cooling effect.
(12) The holes in the hydraulic oil tank, transmission and torque converter etc. are designed to balance the internal pressure within the tank and discharge high temperature gas so as to prevent the temperature from rising rapidly and oil deterioration.
(13) The vent holes in the main reducing gear shell are used to prevent high oil temperature and high air pressure in the shell, thus effectively protecting the seals from being damaged.
(14) The vent hole, oil return hole and compensation hole in the cover of the brake master cylinder ensure supplement and backflow of the braking fluid. Blockage of these holes may cause braking problems and cylinder oil leak.
(15) The small holes in the main clutch and steering clutch are responsible for promptly removing oily d oily dirt from these clutches. If these holes are obstructed, the oily dirt will enter the friction plate surface and thus cause problems such as clutch slippage.