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Home - News - The exhaust valve of the excavator is faulty, it is actually a problem with the hydraulic oil

The exhaust valve of the excavator is faulty, it is actually a problem with the hydraulic oil

April 8, 2021


Dirty impurities in the hydraulic oil can easily lead to high temperature of the hydraulic oil. This situation has a lot to do with the exhaust valve of the hydraulic oil tank. If the exhaust valve (breathing valve) is not replaced for a long time, the hydraulic oil will directly communicate with the outside world. Without the protection of the exhaust valve filter element, the hydraulic oil becomes very dirty.


Exhaust valve function


The exhaust valve is installed above the suction side of the hydraulic oil tank, making the suction side of the oil tank the lowest pressure part in the hydraulic system. It plays the role of ensuring the balance of air pressure inside and outside the hydraulic oil tank during the process of hydraulic oil output and inflow; it can also be said that the exhaust valve plays a "breathing" role, which can filter dust and other impurities in the air to ensure that the hydraulic oil does not Contaminated and deteriorated.


Working principle


The exhaust valve guarantees its normal operation by exhaling and inhaling. For details on how to operate, please see the following:

Exhalation: When the output flow of the hydraulic pump is less than the total flow back to the tank, the air pressure in the tank is higher than the outside air pressure. In order to ensure the balance of internal and external air pressure, air will be discharged to the atmosphere through the exhaust valve, which is called exhalation.


Suction: When the excavator is working, the hydraulic oil flows to the working device, the oil level of the fuel tank is lowered, the air pressure in the fuel tank is lower, and the air pressure outside the fuel tank is higher. , The fuel tank will be dry and deformed, the most important thing is that it will cause the hydraulic pump to reduce the flow rate and slow down the action.


Failure phenomenon


Once the exhaust valve fails and cannot operate normally, the excavator will have the following phenomena:


Abnormal sound of hydraulic pump suction, vibration and noise of pilot oil pipe, abnormal operation of excavator, this situation is mostly caused by blockage of exhaust valve or poor exhaust.

Affect the working efficiency of the hydraulic system, the pressure is unstable, the excavator works sometimes powerfully and sometimes weakly, and the actions are not coordinated.

The hydraulic oil temperature is high, the temperature in the oil tank rises, and the pressure is too high, which will cause the oil tank to crack in severe cases.

The temperature of the hydraulic oil is too dirty, and there is more dust around the exhaust valve and the outer wall of the oil tank, indicating that there are too many impurities attached to the exhaust valve filter element or the filter element has been damaged, which affects the filtering effect; the same hydraulic oil is too dirty and too much impurities will also cause The hydraulic oil is hot.



It is also very simple to avoid problems with the exhaust valve filter element, and it is easy to replace it. You can replace it yourself.

Note for replacement:


1. After the excavator is parked as required, stop the engine and place the safety lock lever in the locked position. (It is necessary to prevent high temperature burns of hydraulic oil!)


2. Please pay attention to the tightening torque; if it is tightened too tightly, it will cause the bolt to break.


First check whether the exhaust valve assembly is damaged. If it is damaged, it needs to be replaced directly.


If the exhaust valve assembly is intact, check the exhaust valve filter element, which is generally replaced every 1000 hours.


If the filter element is damaged or dusty, the filter element needs to be replaced directly.