Routine maintenance method of hydraulic excavator engine thermostat
According to the different engine coolant temperature, the engine thermostat of hydraulic excavator has three different forms, namely, the small cycle of the thermostat, the large cycle of the thermostat and the mixed cycle of the thermostat
Thermostat mixing cycle: when the coolant temperature reaches the specified value (e.g. 76 ~ 86 ℃), the paraffin begins to melt and gradually turns into liquid, and the volume increases and compresses the rubber tube to make it shrink. When the rubber tube shrinks, the push rod acts with an upward thrust. Since the upper end of the push rod is fixed, the push rod generates a downward thrust against the rubber tube and the temperature sensor to open the valve At this time, part of the coolant flows back to the engine through the radiator and thermostat valve, and then flows back to the engine through the water pump. The rest of the coolant flows directly back to the engine through the water pump for mixed circulation of the coolant
Small circulation of thermostat: when the engine of the hydraulic excavator is just started and the coolant temperature is lower than the specified value (e.g. 76 ℃), the paraffin in the temperature sensing body of the thermostat is solid. The thermostat valve closes the channel between the engine and the radiator under the action of the spring, and the coolant returns to the engine through the water pump for small circulation of the coolant
Large circulation of thermostat: when the temperature of the engine coolant of the hydraulic excavator continues to rise and reaches a certain temperature (e.g. 86 ℃), the thermostat push rod fully opens the valve and closes the coolant channel 4. All the coolant flows back to the engine through the radiator and the thermostat valve through the water pump for large circulation of the coolant
If the main valve of the hydraulic excavator engine thermostat is opened too late, the excavator engine will overheat If the main valve of the engine thermostat of the hydraulic excavator is opened too early, the engine preheating time will be prolonged and the engine temperature will be too low When the engine starts cold running, if the coolant still flows out from the water inlet pipe of the upper water chamber of the water tank, it means that the main valve of the thermostat cannot be closed; When the engine coolant temperature exceeds 70 ℃, no coolant flows out from the inlet pipe of the upper water chamber of the water tank, which means that the main valve of the thermostat cannot be opened normally, and repair is required
Inspection after coolant temperature rises: at the beginning of engine operation, the coolant temperature rises rapidly. When the coolant temperature gauge indicates 80 ℃, the temperature rise speed slows down, indicating that the thermostat works normally On the contrary, if the coolant temperature keeps rising rapidly, when the internal pressure reaches a certain level, the boiling water suddenly overflows, which indicates that the main valve is stuck and suddenly opens When the coolant temperature gauge indicates 70 ~ 80 ℃, open the radiator cap and radiator drain switch, and feel the coolant temperature by hand. If it is hot, the thermostat works normally; If the coolant temperature at the radiator water inlet is low, and there is no water flowing out or little water flowing from the water inlet pipe of the radiator upper water chamber, it indicates that the main valve of the thermostat cannot be opened. The thermostat that is stuck or not tightly closed should be removed for cleaning or repair, and cannot be used
Inspection after the engine is started: open the radiator filler cap. If the coolant in the radiator is calm, it indicates that the thermostat works normally; otherwise, it indicates that the thermostat works abnormally This is because when the coolant temperature is lower than 70 ℃, the expansion cylinder of the thermostat is in a contracted state and the main valve is closed; When the coolant temperature is higher than 80 ℃, the expansion cylinder expands, the main valve gradually opens, and the circulating water in the radiator begins to flow When the coolant temperature gauge indicates below 70 ℃, if there is water flowing at the radiator inlet pipe and the coolant temperature is warm, it indicates that the main valve of the thermostat is not tightly closed, which makes the coolant circulate too early
