Training Presentation

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Training Presentation
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Bulldozer Hydraulic System
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• CONTENTS
• Hydraulic System Principles
• Hydraulic System Assembly
• Malfunctions Analysis and Solving
• Pressure Measurement to Diagnose hydraulic system

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Chapter OneHydraulic System Principles
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Hydraulic System Principles

• Hydraulic Components
• Input Pumps
• Output Cylinders, Motors
• Controls Valves
• Ancillary Equipment Oil tank, Piping,
  Filters, Oil Cooler

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Transmission Steering Hydraulics

• SD22 SD32 Hydraulic System
• Transmission and steering control systems
  are separated to each other, they draw oil from
  different pumps, but all the oil is from steering
  clutch case. The oil flows to the torque
  converter after transmission and steering, then
  the oil flows back to steering clutch case.
• So, the transmission and steering are one
  system called transmission steering hydraulic
  system.

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SD22 Hydraulic System
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Transmission Steering Hydraulic System

• SD16 Hydraulic System
• Transmission and Steering control systems draw
  oil from Transmission case and Steering clutch
  Case. Oil flows to torque converter after
  transmission, then to transmission pan again
  through oil cooler. However steering clutch oil
  flows back to steering clutch case.
• So, the transmission and steering are two
  different systems.

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SD16 Transmission System
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SD16 Steering and Brake System
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Chapter TwoHydraulic System Assembly
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Assembly Operation

• Gear Pump
• Bulldozer Transmission Steering Pumps are
  high pressure gear pumps. Their construction is
  simple and very efficient.
• Transmission Valve
• SD22, SD32 have the same transmission valve
  unit. It is consists of Relief Valve, Return
  Valve, Pressure Reduction Valve, Speed Control
  Valve, Safety Valve and Direction Valve.
• Relief Valve Return Valve are for
  transmission oil pressure, Speed Control Valve is
  for shift change, Direction Valve is for Forward
  and Reverse, Pressure Reduction Valve is for
  First Shift, Safety Valve is for protection of
  starting machine.

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SD22, SD32 Transmission Valve
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• SD16 transmission valve has no Safety valve, but
  other 5 valves structure and principle are same
  as SD22 and SD32.

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SD16 Transmission Valve
To Torque Converter
From Pump
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• Modulating Relief Valve
• The modulating relief valve controls the buildup
  of oil pressure when the gear shift lever is
  operated and the clutch engaged, so as to avoid
  shock during start and off and improves the
  service life of power shift transmission.

Modulating Time
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• Steering Valve
• SD32, SD23, SD22 and SD16 steering valves
  structure and principle are the same.
• Steering brake hydraulic system includes relief
  valve, steering control valve, brake booster
  valve.
• they have a bypass/relief valve, to avoid
  abnormal oil pressure if the filter is clogged.

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Steering Relief Valve
Steering Valve
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Work equipment control system
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Relief Valve
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Chapter ThreeTroubleshooting Problem Solving
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Methods of Troubleshooting

• Hydraulic system problems are caused by many
  factors.
• The Process of identifying a problem
• Watch ?Test Machine ?Check Pressure
• Resolving the problem
• a. Refer to Operation or Shop Manual
• b. Carry out adjustments/fit replacement parts

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Transmission Problems Solving
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1. Gearshift inoperative
Reason a. Inner Transmission Box 1. the
gearshifts cylinder seal damaged or
installed wrong 2. Oil path leak 3. if
First Shift is inoperative 1) Ball of
anti return valve is broken 2) Oil path
rotating seal ring is damaged b. Hydraulic
system 1. the 5 O-rings of clutch oil
entrance in the seat of transmission
valve are damaged 2. the factors of the
pressure reduction valve If the pressure
reduction valve is blocked at closed position,
1st gearshift is inoperative if the pressure
reduction valve piston hole is blocked, the oil
pressure will increase, leading to worn seals,
the 1st gearshift is inoperative.
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2. The machine drives on Neutral Gearshift

• Reason
• Incorrect adjustment of the direction valve
  position
• Forward and reverse clutch disc distorted or
  broken, it locked, the clutch cant separate
  completely.

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3. The machine will not drive

• Reason
• The machine will not drive on any gearshift
  position, its because the clutch cant get oil.
• Transmission pump damaged, it cant draw oil.
• Transmission pump seal leak.
• Transmission case oil level is down.
• Oil piping leak, problem with pump.
• Relief valve is blocked, 5 clutches have no oil
  pressure.

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4. Gearshift Lag

• Reason
• the clutch cant get oil, suction piping leak.
• Relief valves relief spring is broken, it delays
  the pressure increase in time.

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5. Hot machine no drive, but cold machine is
normal.
Reason The suction pipe is aging or worn or
distorted, and the suction ability is not
good. The oil is thin, clutch cant engage
properly, so the hot machine has low power.
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6. Transmission Torque Reduced
Reason Relief valves blocked, the valve cant
move correctly, the oil pressure is low and the
clutch cant engage.
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7. Torque converter over heating

• Reason
• Torque converter problem
• 1. return oil pump filter is blocked
• 2. the seal leaking
• Hydraulic system problem
• 1. oil quality is not good
• 2. oil quantity is low, or oil leak
• 3. insufficient cooling.

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8. Steering filter cover bulged
Reason Relief valves blocked or inlet
blocked, the high pressure bulges the cover. Must
clean the relief valve.
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9. Poor Steering Control
Reason Pulling the steering lever to the end
and the pressure normal, the reason is that
steering lever is adjusted incorrectly.
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10. One side no steering, another side is normal

• Reason
• S tube o-ring is damaged
• Clutch intake oil rotation seal is damaged
• Clutch piston seal is damaged

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11. Cold machine has steering, but hot
machine has not steering

• Reason
• The tube between steering pump and filter is
  damaged, so oil cant pass through.
• The oil becomes thin as the machine warms up, or
  the seal is worn, oil leak, oil pressure decrease.

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12. Pulling one steering lever, the machine will
stop
Reason This phenomenon shows that another side
cant transfer power, maybe another side steering
direction valve block at open position.
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13. Sometimes steering is intermittent
Reason Steering suction oil system seal is
damaged and steering pump cant get enough oil,
the pressure is down. Due to steering pump
drawing air, the oil filter has not oil, it leads
transmission pump to draw air too. So sometimes
transmission failure is caused by steering system
damage. When the pump draws air, there are sharp
whistle, and there are many air bubbles in oil.
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14. Braking is poor

• Reason
• Brake band is worn out, need adjustment or
  replacement
• Brake linkage are adjusted incorrectly
• Brake booster valve dont seal well

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15. Pushing force is poor

• Reason
• Engine
• Torque Converter
• Transmission
• Steering Clutch

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15. Pushing force is poor

• Check for the position of problem
• If the universal joint rotates, the malfunction
  is after engine or torque converter.
• If the universal joint does not rotate, then the
  malfunction is before transmission or steering
  clutch.
• If bevel gear rotates, the problem is at steering
  clutch if bevel gear does not rotate, the
  problem is at transmission.

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15. Pushing force is poor

• Check for the Pressure
• If the pressure is right, it must be that there
  is mechanical malfunction or inner failure.
• If the pressure isnt normal, we must diagnose,
  by referring to the manual.

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Chapter FourPressure Measure for Diagnosis
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Pressure Measurement to Diagnose hydraulic
problems

• 1. Important Measurements
• a. Oil brand, quality and grade are correct,
  steering case oil level correct
• b. Warm-up engine, ensure coolant and oil
  temperature are in 70-90oC
• c. Engine is at operating speed
• 2. Measurement Method
• Measure the oil pressure at engine full speed
  and idle speed.
• 3. Measure Points, Standard Pressure (theoretic
  data in manual)

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Examples for Diagnosing Pressure Measurements
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• Machine will not move on selecting a gear
• Measure relief valve pressure low is 0.1, full
  speed is 0.3MPa.
• Due to this low pressure, gear clutch cant get
  enough force, the machine cant move.
• Discharge the air in steering filter, the
  pressure raised, but once engine stops 10 minutes
  later start again, the pressure is low again.
  This means that air is in the pump, replace the
  O-ring, and the problem is solved.

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2. Speed is low in any gear Measure transmission
relief valve pressure low is 0.4MPa, full speed
is 0.7MPa Due to this low pressure, discharge the
air from filter, it is not helpful. Then check
the return valve, then find the valve piston is
blocked, the oil is leaking from output. Clean
the valve piston, reset it again, the problem is
solved.
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3. Power is down on the mid rpm Measure
transmission relief valve pressure low is
1.0MPa, full speed is 3.5MPa, the pressure
changed too much with increased engine speed, it
means that the relief valve need to be adjusted.
After checking, finding the valve piston is
blocked with many carbon and corrupted hollows.
After cleaning valve piston, reset it again, the
problem is solved.
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4. Torque converter power decrease Measure
transmission and steering relief valve pressure
both are normal. Measure the entrance of torque
converter, the oil pressure is 0.4MPa Check
torque converter safety valve, if spring is
broken, replace it, the problem is solved.
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5. If hydraulic oil temperature high, long term
working, then the valve will block
easily Measure transmission valve, the pressure
is normal. Measure the entrance of torque
converter, low speed pressure is 0.1MPa, full
speed oil pressure is 0.5MPa. Due to the entrance
pressure being low, the oil flow is low and
cooling poor, so the temperature is high. Check
torque converter, check the seal of inner oil
path for damage, replace it, the problem is
solved.
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6. No steering at low speed, but at increased
engine rpm, the steering is ok. Measure steering
relief valve pressure low speed pressure is
0.4MPa, full speed oil pressure is 1.1MPa And
steering clutch oil pressure is low. At the same
time the valve is faulty. It means that steering
relief valve is the problem, check it, if the
spring is broken, replace it, the problem is
solved.
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7. Cold machine steering is normal, but after
working, the steering is very heavy Measure
steering relief valve pressure low speed oil
pressure is 0.5MPa, full speed oil pressure is
1.1MPa Steering relief valve oil pressure is
low, it is caused by a blockage of relief
valve. Disassemble and clean it, the problem is
solved.
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8. One side steering is not serviceable
Steering relief valve pressure is normal, other
side steering brake pressure is normal too, but
this side steering brake pressure is low. It show
this booster or its piping has a leak.
Disassemble booster, check the piping entrance
o-ring is damaged, replaced it, the problem is
solved.
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The End of This Training Module Thanks Your
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