1. Training Presentation

2. Bulldozer Hydraulic System

3. CONTENTS
Hydraulic System Principles
Hydraulic System Assembly
Malfunctions Analysis and Solving
Pressure Measurement to Diagnose hydraulic system

4. Chapter One Hydraulic System Principles

5. Hydraulic System Principles
Hydraulic Components:
Input: Pumps
Output: Cylinders, Motors
Controls: Valves
Ancillary Equipment: Oil tank, Piping, Filters, Oil Cooler

6. 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.

7. SD22 Hydraulic System

8. 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.

9. SD16 Transmission System

10. SD16 Steering and Brake System

11. Chapter Two Hydraulic System Assembly

12. 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.

13. SD22, SD32 Transmission Valve

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

15. SD16 Transmission Valve
To Torque Converter
From Pump

16. 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

17. 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.

18. Steering Relief Valve
Steering Valve

19. Work equipment control system

20. Relief Valve

22. Chapter Three Troubleshooting & Problem Solving

23. 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

24. Transmission Problems Solving

25. 1. Gearshift inoperative
Reason:
a. Inner Transmission Box:
1. the gearshift’s 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.

26. 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 can’t separate completely.

27. 3. The machine will not drive
Reason:
The machine will not drive on any gearshift position, it’s because the clutch can’t get oil.
Transmission pump damaged, it can’t 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.

28. 4. Gearshift Lag
Reason:
the clutch can’t get oil, suction piping leak.
Relief valve’s relief spring is broken, it delays the pressure increase in time.

29. 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 can’t engage properly, so the hot machine has low power.

30. 6. Transmission Torque Reduced
Reason:
Relief valves blocked, the valve can’t move correctly, the oil pressure is low and the clutch can’t engage.

31. 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.

32. 8. Steering filter cover bulged
Reason:
Relief valves blocked or inlet blocked, the high pressure bulges the cover. Must clean the relief valve.

33. 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.

34. 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

35. Reason: 11. Cold machine has steering,
but hot machine has not steering
Reason:
The tube between steering pump and filter is damaged, so oil can’t pass through.
The oil becomes thin as the machine warms up, or the seal is worn, oil leak, oil pressure decrease.

36. 12. Pulling one steering lever, the machine will stop
Reason:
This phenomenon shows that another side can’t transfer power, maybe another side steering direction valve block at open position.

37. 13. Sometimes steering is intermittent
Reason:
Steering suction oil system seal is damaged and steering pump can’t 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.

38. 14. Braking is poor Reason:
Brake band is worn out, need adjustment or replacement
Brake linkage are adjusted incorrectly
Brake booster valve don’t seal well

39. 15. Pushing force is poor Reason: Engine Torque Converter Transmission
Steering Clutch

40. 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.

41. 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 isn’t normal, we must diagnose, by referring to the manual.

42. Chapter Four Pressure Measure for Diagnosis

43. to Diagnose hydraulic problems
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)

44. Diagnosing Pressure Measurements
Examples for
Diagnosing Pressure Measurements

45. 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 can’t get enough force, the machine can’t 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.

46. 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.

47. 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.

48. 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.

49. 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.

50. 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.

51. 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.

52. 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.

53. The End of This Training Module
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