WEICHAI WD10 Service Manual - page 159
Service Manual for WD10 Diesel Engine
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4) If the steering wheel is easy to turn at low oil temperature, but hard to turn after oil temperature
raised, we divided this fault into two kinds:
a) Easy steering after cold start, but hard to steer after the vehicle is warmed up:
The problem indicates that the pump and steering gear is in good condition. But oil
viscosity tends to be much smaller under high temperature and high system pressure
(mainly caused by overloading and rapid steering), and the oil can cap will be burst out
under high oil pressure and temperature, the driving safety is at risk. The only to solve this
problem is to cool the steering system, such as improve heat dissipation by adding extra
radiating device, and refresh the steering system oil (Old oil mustn’t be reused). Do not
overload the system for too long and avoid long time extreme steering.
According to our experience, replace the pump or steering gear wouldn’t solve the problem,
the only suggestion is to improve heat dissipation and avoid long-time overloading and
extreme steering. Do not replace the pump or steering gear.
b) Hard steering no matter it is cold start or hot start:
The problem indicates that there is damaged part or oil shortage in steering system, refer to
other normal diagnoses to solve this problem.
Generally, a pressure gauge is needed to measure steering system pressure to determine
part damage condition.
5) Poor sealing performance of steering gear oil seals, leads to internal leakage or blockage and
damage of steering gear control valve. Replace the steering gear.
6) Due to pressure control valve of steering system is designed in steering gear, we can detect
steering system pressure with pressure tester, to check whether the reading changes as the
steering wheel rotates; or adjust pressure tester regulating valve to check whether reading
changes along with the adjustment of regulating valve.
7) For high oil pressure problem, which is generally caused by overloading and long-time extreme
steering, result in the system fails to dissipate the heat effectively and timely. Currently, more
than 80% heavy truck fault is caused by this.
(3) Steering pump and steering system produces abnormal noise
Fault phenomenon: Abnormal noise occurs when steering.
Possible causes:
1) Air in steering system, low oil level in oil cup, oil leakage and blockage of oil cup filter
element, which lead to steering pump oil absorption problem.
2) Overloaded system results in high oil temperature, and produces noise.