5 Best Practices for the Use and Maintenance of Principal Assembly
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Use and Maintenance of Principal Assembly

Steering system

1. Mechanical steering

Mechanical steering
  • The steering operation system is composed of steering wheel, steering shaft, universal joint and steering column assembly. The diameter of steering wheel is Φ450mm.
  • The steering gear is ZF8098 power steering gear. ZF8098 is an integral hydraulic power steering gear, and the control valve is rotary valve structure. It adopts the variable-speed ratio transmission and can automatically adjust the hydraulic steering limit valve. It is provided with a built-in pressure safety valve, and the adjustable pressure is 170+13 bar, which can effectively protect the steering pump and steering system, and improve the service life of steering system parts.
Use and Maintenance of Principal Assembly

Fully hydraulic steering

1. Steering schematic diagram

  • Hydraulic oil tank
  • Steering oil pump
  • Steering gear
  • Left steering oil cylinder
  • Right steering oil cylinde

2. Hydraulic schematic diagram

  • (1) System unloading pressure 175Bar
  • (2) Rated discharge 60LPM
  • (3) Maximum operating temperature 93℃
  • (4) Allowable temperature difference with the system 28℃
  • (5) Maximum allowable manual steering torque 136NM
Use and Maintenance of Principal Assembly

3. Precautions for use

Guarantee clean to prevent dirt entering the hydraulic system.

  • (1) The oil pipe connector shall not adopt Teflon tape, etc. for sealing.
  • (2) The input end of steering gear shall avoid bearing axial force.
  • (3) The liquid level of oil tank shall be checked frequently, and the filtering element and hydraulic oil shall be replaced regularly.
  • (4) The steering wheel may reach the terminal point after is turned to left, right for 2-3 circles, indicating that the fully hydraulic steering device has no steering return function.

4. Hydraulic oil

1. Replace the hydraulic oil

2. Oil discharge specification

  • (1) Jack up the front axle, and loosen the oil inlet pipe and oil return pipe on the steering gear.
  • (2) Start the engine for short-time operation (at most 10 seconds) to suck oil out of the oil pump and oil tank.
  • (3) Use a container to hold the oil discharged.
  • (4) Reconnect the oil inlet pipe and oil return pipe.
  • (5) Open the oil return hole bolt at the steering gear bottom.
  • (6) Turn the steering wheel repeatedly until no oil discharge.

3. Keep the hydraulic oil clean
Check the oil level height and the hydraulic oil cleanness once every month.
4. Check the rotating components
The clearance of each rotating component shall be checked for every maintenance, such as steering tie rod, straight rod joint. The component shall be replaced in case of too large clearance. The lubricating grease shall be filled in each part during maintenance.

IV. Transmission control system

Automatic gearbox

1. Main structure

2. Gearbox oil

(1). Gearbox oil and fueling
  • a. Oil standard: It is recommended to use the synthetic oil dedicated for Allison transmission jointly researched and developed by Allison Company and
    Castrol Oil Company: standard of TranSynD TM .
  • b. Oil filling: The oil consumption for this series transmission varies with the change of oil pan depth and external piping, and will be finally confirmed according to the oil level inspection procedure.
  • c. Fueling procedure: Unplug the oil scale in the oil filler pipe, and place it in a clean place Fill the qualified gearbox oil to be within the oil gauge range, then check the oil level.
  • Note: Do not bring sundries in the gearbox when fueling and checking the oil.
(2). Oil level inspection
  • a. Oil gauge: For the oil gauge scale as shown in Figure 12.2, the range between characters of COLD ADD and CALD FULL is oil level of cold oil level, in the lower part of the oil gauge, while the range between characters of HOT ADD and HOT FULL is hot oil level, above the cold oil level.
  • b. Cold inspection: The so-called cold inspection is the oil level inspection when the gearbox oil temperature is ambient temperature (16-49℃). The purpose of cold inspection is to have sufficient gearbox oil for hot inspection. The steps are as follows:
  • 1) Park the vehicle on the level ground.
  • 2) Place the gearbox in the neutral position to start the engine.
  • 3) The engine returns for idling after running 1 minute at the speed of 1000-1500r/min. The gearbox enters the forward gear for running 1 minute again. At this moment, the oil temperature shall be within 16-49℃.
  • 4) Wait for a period of time to make the oil level balanced, take out the oil gauge, and check to confirm the oil level in the cold position, namely between COLD ADD and CALD FULL. Otherwise add or discharge to make it reach this position. Oil gauge Oil filler pipe Hot oil level Cold oil level Oil gauge scale Figure 12.2
  • c. Hot inspection: The so-called hot inspection is to check the gearbox oil level when the gearbox oil temperature reaches 71-93℃ for the first time. At this
    moment, take out the oil gauge, and the oil level shall be in the hot position, namely between HOT ADD and HOT FULL. Otherwise add or discharge to make it reach this position.

(1) Grasp and pull the handle down to close the engine hood, and the hood is automatically locked.

Power take-off


The power take-off is a set of transmission gears, also known as power output device, which provides power for the equipment requiring extra power. The
power take-off for port vehicles is mainly used for saddle lifting system, and services as the power source of
lifting pump. Generally the engine rear power take-off method is adopted. PR70 power take-off is optional for ZF
mechanical transmission model.

PR70 power take-off (Figure 12.4)

  1. Output location: upper right output
  2. Speed ratio of power take-off: 2.12×0.789=1.673
  3. Output speed: 2,300rpm (rated engine speed)/1.673 (total speed ratio)=1,375rpm (output transmission speed
    of power take-off)
  4. Rotating direction: left-handed rotation (viewing from the output end of power take-off), in the same direction
    with engine
  5. Output mode: internal spline, major diameter of 25mm, minor diameter of 20.1mm, tooth space width of 6mm
  6. Rated output torque: 700Nm
  7. Recommended oil pump: CB-HJH series gear pump (Xuzhou Construction Machinery), the users may choose
    as needed, and direct connection is available.

Use maintenance

When the gear meshing of transmission mechanism connected with the power take-off is poor, and the related connecting bolts of power take-off is loose, the abnormal sound will occur. Check the fastening bolt of each component; meanwhile, pay attention to viewing the conditions of lubricating oil, clean the dirt promptly, and keep each component clean, intact, without collision, scratch. In addition, check the connecting pipe between power take-off and oil pump frequently, and if there is looseness, damage, falling, fracture, replace promptly.


Front Axle

1. Structure overview

The front axle (as shown in Figure 13.1) is a fist type I-shape rigid special front axle, which is mainly composed of the middle front beam and the knuckle and hub, etc. hinged at both ends of the front beam. The front beam is the integral forging fist-type I-shape beam, and its middle part adopts the concave curve structure. The titling both ends on the front beam present the fist shape, and the round hole on it is used for installing master pin, thus the inclination angle of master pin is guaranteed.

2. Maintenance of front axle

  • The front axle shall be maintained regularly for every traveling of 15,000km or for every six months. The following fasteners shall be tightened regularly according to the required tightening torque.
  • Check the rotation conditions of hub bearing, and replace the lubricating grease; meanwhile, check whether the hub bearing can be used continuously, and adjust or replace if necessary. The lubricating grease for hub bearing, brake camshaft and master pin, tie rod ball pin, brake clearance adjusting arm, etc. is the general purpose lithium base grease for automobile.
  • Usage of lubricating grease:
    (1) Usage of lubricating grease for each hub: a total of about 0.6kg for hub inner chamber, two bearings;
    (2) Usage of lubricating grease for each brake camshaft and master pin: about 0.2kg, use an oil gun to fill until spillover of bracket hole;
    (3) The tie rod ball pin, brake clearance adjusting arm, etc. shall be fully filled with lubricating grease.
  • The following items need to be checked regularly, as shown in Table 1. The parameter requirements are shown in Table 2.

Drive axle

Rear axle overview

The Steyr ST16 rear drive axle is the central one-level reduction and wheel planetary reduction two-stage drive axle, with the total speed ratio of i=10.77. According to different drive types, there are also duplex drive axle and single rear axle two kinds. The steel plate punched axle housing makes the drive axle and vehicle have better matching attribute.

Rear axle maintenance

1. Fueling and oil changing

Figure 13.2 After traveling 5,000km, replace the lubricating oil filled when assembling, and check the oil level once for every traveling of 5,000km or for every month; Replace the lubricating oil once for every traveling of 150,000km or for every year; Replace the lubricating grease for brake adjusting arm and camshaft once for every traveling of 150,000km or for every year. Oil name: GL-585W-90 gear oil; oil filling: 23L (middle axle), 20.5L (rear axle).

2. Axle maintenance
  • a. Clean the dirt, dust on the rear axle breather plug frequently.
  • Check the oil filler plug and oil drain plug frequently, and if there is oil leakage, tighten or replace the sealing washer promptly.
  • As the half axle flange transmission torque is torque, and there exists the impact load, check the fastening condition of half axle bolts to prevent looseness and fracture of the half axle bolts arising therefrom.
  • For every traveling of 2,000km, fill 2# lithium base grease in each grease nipple, clean the breather plug, and check the gear oil level height in the axle
    housing (open the oil filler plug on the axle housing rear cover for inspection).
  • For every traveling of 5,000km, check the brake clearance.
  • For every traveling of 8,000-10,000km, check the fastening condition of brake bottom plate, and check the looseness of hub bearing. Check the wear
    condition of brake pad, and if the wear of brake pad exceeds the limiting pit, replace the brake pad. Check the quality of gear oil in the axle housing, and if there is deterioration or thinning, replace with new oil promptly. The initial oil changing mileage is 8,000km; later, replace the gear oil for every traveling of 24,000km.

Brake system

Brake system structure requirements

  1. Functions required for the brake system: service brake, parking brake, emergency brake;
  2. The service brake must be dual circuit system.
  3. The service bake must function on all the wheels, with even braking effect.
  4. The brake control must have the function of gradual advance.
  5. There must be an audio (or) optical alarm device structurally.
  6. If one circuit fails, the other circuit pressure must be protected to make the residual brake force can effectively stop the vehicle.

Main structure of brake system

1. Air compressor
  • The air compressor is air source for the entire vehicle gas path. At present, Sino Truck equips with WABCO double-cylinder air compressor that has the synchronous level with Europe’s most advanced heavy-duty truck engine, and under the Europe’s service conditions, its service life reaches 1500,000KM.The single-cylinder air compressor is in the high load operating state for long time due to small discharge capacity, thus easily causing break of crankshaft, linkage of air compressor and large expelling of engine oil. The double-cylinder air compressor has large discharge capacity and short operating period, which greatly improves reliability, life of the air compressor itself, thus reducing the power consumption.
  • The temperature and oil expelling of compressed air are obviously reduced, causing the reliability of various valve components of the truck brake system are promoted greatly, then the safety and maneuverability of entire vehicle will become better. Under the traveling condition of descending a long slope, the compressed air can be made up promptly to ensure there is sufficient compressed air in the brake system, and ensure the traveling safety.
2. Air processing unit (APU)
  • APU (as shown in Figure 9.1) is an assembly of air dryer and four circuit protection valve. The air dryer uses molecular sieve as desiccant to clean, dry the compressed air from the air compressor. The built-in reflux valve substitutes the 5L air reservoir, which saves more installation cost and installation space. The reflux valve allows a certain amount of pressure to blow back the drying cylinder, and the back flowing process is controlled through accurate pressure difference. The four circuit protection valve is used for restricting and protecting the system pressure. Therefore, APU provides a complete, simple, effective air processing system for the automotive air brake system.
3. Main control valve

The main brake valve is a device used to control and manipulate the main brake system work, and to make the brake pressure and brake controlling force (or pedal travel) form a certain proportional relation. The internal combustion tractor adopts the double circuit dual-chamber main brake valve.

4. Brake relay valve
  • The function of main brake relay valve (as shown in Figure 9.2) is to shorten the brake reaction time, which plays the role of “fast charge” and fast discharge for the main brake chamber. With long axle base, large total capacity of automobile (middle) rear axle brake chamber, and long distance to the main brake valve, therefore, the brake reaction time from the brake pedal being pressed down to reaching the corresponding value of chamber pressure is too long. Thus a relay valve is installed in the nearest position to the (middle) rear axle brake chamber, which is supplied of air directly by the air reservoir through a thick main piping, then is controlled by the main brake valve through a thin piping.
5. Brake chamber
  • The function of front brake chamber is to input different pressure and produce different thrust, then through the brake cam and brake shoe, the brake drum will produce braking of different strength to the front axle. The middle rear axle is a combined brake chamber, and its function is not only to produce effect on the (middle) rear axle main brake, but also to implement the parking and emergency brake.

Brake system fault and solution

Brake failure

Causes and removal methods
1. Insufficient pressure in the gas path:
  • Poor sealing of suction and exhaust valve of the air compressor, gasket damage, replace the valve or spring, and replace the gasket in case of damage.
  • Damage of air tube or air tube joint, replace the air tube or joint.
  • Leakage of four circuit protection valve, after the valve dismantling, clean each machine part, and check the leak tightness after replacing the damaged part.
  • Leakage of relay valve, after the valve dismantling, clean each machine part, and check the leak tightness after replacing the damaged part.
  • Leakage of main brake valve, after the valve dismantling, clean each machine part, and check the leak tightness after replacing the damaged part.
  • Leakage of parking brake valve, after the valve dismantling, clean each machine part, and check the leak tightness after replacing the damaged part.
2. Poor sealing of suction and exhaust valve of the main brake valve, clean the suction and exhaust valve, and replace if necessary.
3. Poor sealing of suction and exhaust valve of the relay valve, after the valve dismantling, clean each machine part, and check the leak tightness after
replacing the damaged part. If the valve is damaged, replace it.
4. Damage of brake chamber diaphragm, replace the diaphragm.
5. Too large brake clearance, readjust the brake clearance as required, and if necessary, replace the lining.
6. Oiliness or burning hardening of brake lining, replace the brake lining or oil seal, and eliminate the oil leakage phenomenon.

No reliving or incomplete relieving of brake

Causes and removal methods
  1. Blocking of main brake valve relay piston or slave piston, after dismantling the main brake valve, check the piston, sealing ring and its operating surface, and replace the piston or sealing ring.
  2. Shriveling of plastic pipe from main brake valve to relay valve, causing the air venting obstructed, check the piping of this section, and replace if necessary.
  3. Blocking of relay valve piston or exhaust valve, after dismantling the relay valve, check the piston, sealing ring and exhaust valve, and if necessary, replace the repair kit.
  4. Leakage of hand brake chamber, dismantle, check and repair the hand brake chamber.
    5. Leakage of hand brake valve, dismantle and check the hand brake valve.
  5. Inhibited air return of main brake valve, relay valve, dismantle, check and repair.
  6. Camshaft unsmooth, check the movement condition of camshaft, and if necessary, dismantle and check.
  7. Insufficient elasticity of return spring of brake pedal, replace the spring.
  8. Too small brake clearance, readjust the brake clearance.

Braking deviation

Causes and removal methods
  1. The tire pressure does not meet the requirements; check the tire pressure.
  2. The tire type is not consistent; install the same type of tire.
  3. The brake clearance adjustment is not correct; readjust the brake clearance.
  4. The brake shoe wear is uneven; replace the brake shoe, and polish it if necessary.
  5. There is oil stain on the brake shoe of some side; clean with gasoline, and replace if necessary.
  6. The material, model of each brake shoe are not consistent; replace the brake shoe of the same model, material.
  7. The brake chamber of some side does not work normally; repair or replace the brake chamber.
  8. The brake drum is out of round; bore the brake drum.

Central control system

  • a) Keep the vehicle in good condition, and do not drive the defective vehicle!
  • b) When installing this control system, ensure that the circuit system is well earthed.
  • c) When operating, extremely avoid the hot plugging behavior. When carrying on welding work on the vehicle or nearby, disconnect the battery power and unplug all electrical connectors, such as CBCU, electrical junctions’ box, instrument, ECU of engine and ECU of ABS, etc.

Overview of central control system

  • The HOWO VDO bus control system structure chart is as shown in Figure 11.1, and the constituting components include vehicle body central computer
    (CBCU), menu knob / switch, combination instrument (CMIC), travel detector (VDR) (optional). The vehicle body central computer can be connected with other modules with the CAN communication function, such as power bus conforming to SAE-J1939.
  • The function of externally connected nodes can be extended according to the future loading need. System advantages: The combination instrument can be controlled flexibly through the vehicle body central computer, all functions can be completed through PLC programming, and the customer personalized requirements can be realized easily. The system has high reliability. Operation cautions: The charged assembly and disassembly of the instrument is strictly prohibited! Otherwise the instrument, wiring harness may be damaged (such as causing the terminal burning, and causing the data loss).
  • The sufficient protection must be provided for cable layout.
  • The line on CBCU must be disconnected during welding, etc.
  • Turning off the power switch is strictly prohibited during the engine operation.
  • CBCU opening, flushing and measuring are strictly prohibited.
  • The supply voltage must be kept within the range of operating voltage.
  • Before the battery line is firmly connected, connecting power and starting engine are strictly prohibited.
  • The battery electrolyte boiling is strictly prohibited.
  • Touching the CBCU terminal with hand or other conductor is strictly prohibited.
  • All operations that may produce too high instantaneous induction voltage due to load discharging are strictly prohibited.
  • Pay attention to good earthing connection

Description of central control system function

  • 1. When the vehicle is traveling (vehicle speed of more than 15km/h), if the cab door is not tightly closed, the buzzer will send high-frequency alarm for 30 seconds; meanwhile, the display screen flickers constantly, displaying “please shut the door”.
  • 2. After the power master switch is connected, and when the key is not inserted, all pointers return to zero, and the driving screen flickers a time. The buzzer will not chirp, and all indicator lights will not be lit.
  • 3. After the 15# power supply is connected, all signal lights on the instrument will flicker, and the buzzer will chirp, about 1 second. After the engine start, D+ generation, when the ordinary alarm indicator light is lit, the buzzer will not alarm. If any one of engine oil pressure alarm light, cab lock-up signal light, engine overspeed alarm (more than 2,500r/m), brake pressure 1 signal light, brake pressure 2 signal light, brake pressure 3 signal light is lit, the buzzer will send high-frequency alarm continuously.
  • 4. During the engine operation, turn off the 15# power supply, and the buzzer will send high-frequency alarm; meanwhile, the display screen will display “please stop the engine”.
  • 5. Description of safety belt alarm A.14 on the central control unit (CBCU) is input terminal of the safety belt alarm signal. When the safety belt is not inserted well, there is earth signal input, and after the safety belt is inserted well, the input terminal dangles.
  • a. After the 15# power supply is connected, if the safety belt has been inserted well, the safety belt lock-up signal light on the instrument panel will not be lit. If the safety belt is not inserted well, the signal light will be always lit, and the buzzer will not alarm.
  • b. After the engine starts, if the safety belt is not inserted well, the signal light will be lit, and the buzzer will send low-frequency alarm for 6 seconds, then stop. After the safety belt is inserted well, the signal light will be off, and meanwhile, the buzzer will stop alarming.
  • 6. During the engine operation If the safety belt is pulled out, the signal light will be lit, and meanwhile, the buzzer will have a 6-second low-frequency alarm reminder.
  • 7. Description of air filter blocking alarm After the 15# power supply is connected, if D.37 of the central control unit (CBCU) detects the air filter blocking alarm signal, this alarm light on the combination instrument will be always lit until the key switch 15# is closed, then recheck after power-on. The buzzer will not alarm.

New-type digital CAN instrument

  • The new-type digital CAN instrument is mainly composed of engine tachomerer, speedometer, barometer 1, barometer 2, fuel gauge, water thermometer, information display panel, signal light and knob.
  • The combination instrument is connected with the vehicle body central computer, recorder through instrument bus (ICAN) to display traveling information, error alarm, etc. of the vehicle, then the instrument will display directly on the dial after receiving these signals.
  • The combination instrument internally is set with a buzzer, and it can send alarm when the system fails. During steering or operation of the danger alarm switch, the buzzer also beeps.
  • The instrument surface has a button used for zero clearing of trip distance.

Central control unit (CBCU)4

1. Main tasks of central control unit (CBCU) are as follows:
  • Through CAN port, receive, process and distribute data;
  • Diagnosis function applicable to driver, owner, service personnel;
  • Diagnosis port for the overall electrical network;
  • Special gateway for CAN bus system;
  • Input / output, error handling;
  • Switch digital input and status signal;
  • Frequency input;
  • Sensor analog input;
  • Input of multi-function selector switch;
  • Output to incandescent light bulb and relay;
  • Output of 8V, 5V power for sensor;
  • Input and output error monitoring;
  • Monitoring of CAN bus error information;
  • KWP2000 port used between the vehicle body central computer and KIBES-32 software;
  • Diagnosis information storage;
  • Control instrument (CMIC), including the display content of LCD, etc.
2. Advantages of central control unit (CBCU):
  • The KIBES-32 software may be adopted for flexible programming. KIBES-32 is a highly graphical software based on KIBES-32, and the product developer may make the system programming simply.
  • Without needing to change the CBCU source program, the programmer may realize all functions directly.
  • The customer may realize the system integration.
  • KIBES-32 platform is established with CAN, gateway, etc. function, thus, using CBCU, the function extension of future system can be realized easily.
  • All functions of the instrument are completed through PLC programming, and the professional design to customers can be realized easily.
  • The flexible configuration of all system within the port defined range can be realized.
  • The central computer shall be installed in the cab.
  • The central computer shall not be operated in the inflammable and explosive environment.
  • The charged assembly and disassembly of central computer is extremely prohibited, otherwise the damage to the central control unit (CBCU) and wire harness may be caused (such as causing the burning of terminal in the connector assembly, etc.

Electrical junction box assembly

The electrical junction box assembly integrates the relay, diode, safety, etc. used on the vehicle:

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