The hydraulic system is a core component of the mixer truck. In our after-sales service process, the hydraulic system is also a frequently repaired part. Once a malfunction occurs, it often leads to downtime, or even bigger problems such as tank jamming. Furthermore, hydraulic system repairs are relatively more specialized, and the repair costs are also higher. To reduce the failure rate of the hydraulic system, vehicle owners must understand common faults and causes, as well as maintenance precautions.

　　1. Common Faults and Causes of Hydraulic Pumps and Motors

　　• Oil Leaks

　　Oil seal damage in the control valve, oil leaks due to poor sealing of the front and rear end covers of the replenishing pump;

　　Oil leaks due to poor sealing of the O-ring at the servo cylinder motor oil pipe interface.

　　• Noise

　　Abnormal sounds from the oil pipe pump motor (return oil, intake, resonance).

　　• Drum Doesn't Rotate

　　Unidirectional non-rotation (pull wire not in place, damper plate blockage, servo cylinder damage, swash plate jamming, shuttle valve malfunction, hand control valve pin spring malfunction);

　　Bidirectional non-rotation (hand control valve pin spring malfunction, oil passage blockage, severe oil shortage, filter clogging).

　　2. Common Faults and Causes of Gearboxes

　　• Abnormal Noise

　　Dust cover dry grinding, oil seal with foreign objects, dirty or incorrect oil type, internal faults, etc.

　　• Abnormal Noise Not from Gearbox

　　Loose large-disc fastening bolts, accumulated material in the tank, abnormal noise from the towing wheel track, etc.

　　• Oil Leaks

　　Dust cover wear, poor sealing of the motor stop.

　　• Gearbox Doesn't Rotate

　　Internal fault.

　　3. Hydraulic System Maintenance

　　80% of hydraulic system failures are caused by contamination of the hydraulic fluid; contamination of the hydraulic fluid can lead to failures of system components and the system itself. The main contaminants in the hydraulic fluid are: solid particles, water, and air.

　　Therefore, to reduce hydraulic system failures, the most important thing is to strictly control the quality of the hydraulic oil and avoid the above contaminants from polluting the hydraulic oil;

　　Secondly, strictly follow the requirements of the mixer truck instruction manual and regularly replace the hydraulic oil with the correct grade. In principle, use 68# anti-wear hydraulic oil in summer, 46# anti-wear hydraulic oil in winter, and 32# low-temperature anti-wear hydraulic oil in extremely cold areas.

　　In addition, oil changes and filter replacements also have strict requirements: the first replacement should be carried out after 150 operating hours! Thereafter, replace every 1500 hours, but at least once every six months! When changing the oil, replace the filter element at the same time (only original qualified filter elements are allowed).

　　4. Handling Emergency Situations in Mixer Trucks

　　If the mixing drum stops rotating while loading concrete, and the hydraulic motor and gearbox driving the mixing drum are in good condition, an emergency oil pipe can be used to discharge the concrete. The emergency oil pipe is used as follows:

　　First, connect the emergency oil pipe as shown in the figure;

　　Then, start the engine of the rescue vehicle;

　　Next, move the rescue vehicle's operating handle to the "discharge" position to allow the malfunctioning vehicle to discharge the concrete.