SECTION 35 - HYDRAULIC SYSTEM. Chapter 2 - Variable Flow Hydraulic Pump Assembly

Transcription

1 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 1 SECTION 35 - HYDRAULIC SYSTEM Chapter 2 - Variable Flow Hydraulic Pump Assembly CONTENT Section Description Page Special Tools Specifications Tightening Torques Description and Operation Hydraulic Circuit Operation Low Pressure Standby High Pressure Circuit High Demand High Pressure Circuit Low Demand Controlling Maximum System Pressure Fault Finding Initial Fault Finding Check Transmission Low Pressure Warning Light ON' Charge Pressure Light Intake Filter Restriction Warning Light Power Steering Trailer Brakes Hydraulic Lift Remote Control Valves Pump Pressure and Flow Testing Low Pressure Standby High Pressure Standby Load Sensing Circuit Test Charge Pressure test Variable Flow Piston Pump Flow Test Steering Pump/Low Pressure Pump Test Hydraulic Pump Leak Test Continued Overleaf

2 2 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 CONTENT Section Description Page Overhaul Charge Pressure Valve Charge Pressure Filter Dump Valve Steering Flow Control Valve Pressure and Flow Compensating Valve Pump Removal and Installation Steering Pump Overhaul Charge Pump Overhaul Variable Flow Piston Pump Overhaul Pump Drive Gear and Bearing Overhaul

3 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 3 SPECIAL TOOLS NEW HOLLAND PRIOR TOOL PART No NUMBER Pump Removal Bracket NH Pump Drive Shaft Retainer NH By-Pass and Dump Valve Extractor FT. 857 Pressure Gauge 0-6.6bar (0-100lbf\in 2 ) FT Pressure Gauge 0-414bar (0-6000lbf\in 2 ) FT. 8503A Adaptor Charge Pressure Test NH Hydraulic Pressure Test Kit Adaptor Pump Drive Gear Shaft Pin Removal 50140* Adaptor Pump Drive Gear Shaft Removal Tee Adaptor 1 / 4 ORSF (F) x 1 / 4 ORFS (F) x 7 / 16 UNF (F) Tee Adaptor 3 / 8 ORSF (F) 3 / 8 ORFS (M) x 7 / 16 UNF (F) Adaptor m10x1 (M) x 7 / 16 UNF (F) Adaptor m10x1 (M) x 7 / 16 JIC (M) Cap 1 / 4 ORFS Quick Release coupler Quick Release Adaptor x 7 / 16 UNF (M) Alignment Dowel Local Manufacture Plug (Modify adaptor New Holland Part No ) Flowmeter ltrs/min Procure Locally SEALANT Flexible Gasket Sealant

4 4 Charge Pump Type SECTION 35 - HYDRAULIC SYSTEM - CHAPTER SPECIFICATIONS Gear Type Pump Charge Pressure Filter Dump Valve Crack 6.9 bar (100lbf/in 2 ) Fully 12.4bar (180lbf/in 2 ) Charge Pressure Minimum bar (23-50lbf/in rev/min and variable flow piston pump On Load' Charge Pressure Switch bar (8-12 lbf/in 2 ) Making charge pressure warning light flash Variable Flow Closed Centre Load Sensing Piston Pump Type Variable Flow Piston Pump (Swash Plate Controlled) Minimum 2200 erpm 111 Ltr/min 24 Imp Galls/min 29 US Galls/min Standby Pressure (Low Pressure Standby) 21-24bar ( lbf/in 2 ) Maximum System Pressure (High Pressure Standby) bar ( lbf/in 2 ) Steering/Low Pressure Circuit Pump Type Minimum 2200 erpm Flow to Steering Motor Steering Pressure Gear Type Pump 61.5 Ltr/min 13 Imp Galls/min 16 US Galls/min 22-28ltr/min Imp Galls/min US Galls/min 190bar (2750lbf/in 2 ) max

5 TORQUES SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 5 TIA

6 6 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER DESCRIPTION AND OPERATION Hydraulic Pump Assembly With Variable Displacement Closed Centre Load Sensing 1. Steering, Low Pressure and Lubrication Circuit Gear 2. Gear Type Charge Pump Type Pump 3. Variable Flow Piston Pump 2 The variable flow closed centre load sensing hydraulic pump assembly is mounted on the right hand side of the rear axle centre housing and contains within its body three hydraulic pumps. A charge pump of the gear type to supply oil at a charge pressure of bar (23-50lbf/in 2 ) to a variable flow closed centre load sensing hydraulic piston pump. A variable flow closed centre load sensing piston type hydraulic pump supplying oil to the high pressure circuits for operation of:- Trailer Brake Hydraulic Lift Assembly Remote Control Valves Front Axle Suspension Variable Flow Piston Pump Output on Full 2200 erpm 111 Ltr/min 21 Imp Galls/min 25 US Galls/min A fixed displacement gear type pump, referred to as the Steering and Low Pressure Circuit pump, supplying oil for operation of: Steering System Independent Power Take Off Differential Lock Front Wheel Drive Axle Transmission Clutches Lubrication Circuit Steering and Low Pressure Pump 2200 erpm 61.5 Ltr/min 13 Imp Galls/min 16 US Galls/min

7 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER Spring 2. Spring 3. Seat 4. Swash Plate Variable Flow Piston Pump Pump Components 5. Thrust plate 6. Nine Element Pumping Head 7. End Plate and Servo Piston Assembly 8. Load Sensing Valve 3 Principal of Operation All three pumping elements are driven by a live' drive gear train directly connected to the PTO clutch input drive shaft and driven by the engine flywheel. The operating principal of the fixed displacement gear pumps is to provide a constant oil flow directly related to the rotation speed of the pump. The operating principal of a variable flow piston pump is to provide oil flow on demand and minimises the engine power absorbed in driving the hydraulic pump when the hydraulic circuits do not require maximum pump flow. The variable flow piston pump in hydraulic systems therefore has distinct power loss advantages over fixed displacement gear type pumps, which continually provide oil flow and absorb engine power even when the hydraulic circuits do not require the total pump output. Variable Displacement Piston Pump The major components of the variable flow piston pump with closed centre load sensing are:- 1. A nine element pumping head. 2. A plate mechanism (swash plate) to adjust piston stroke and corresponding pump output. 3. A load sensing valve which monitors the requirements of the hydraulic circuits and signals the pump to increase or decrease hydraulic oil flow accordingly.

8 8 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 1. Pump End Plate 2. Swash Plate Servo Piston 3. Swash Plate 4. Swash Plate Return Spring 5. Driveshaft Gear 6. Driveshaft Variable Displacement Piston Pump-Sectional Drawing 7. Slipper (9 off) 8. Piston and Barrel 9. Inlet Port 10. Pumping Head Pre-load Spring 11. Outlet Port 4 The nine element pumping head is cylindrical in shape and has nine barrels, into each of which, is installed a piston. On the end of each piston is pressed a slipper which always remains in contact with the face of the swash plate located at the front of the pumping head. The drive shaft, which is driven by the pump drive gear, rotates the pumping head. As the pumping head rotates, the pistons move in and out of their barrels, following the contour of the swash plate. For every revolution of the drive shaft each piston completes one pumping cycle. The swash plate, which does not rotate but pivots about the front of the pumping head, is the control mechanism that limits the stroke of each piston and works in conjunction with the pressure and flow compensating valves in the load sensing line. As the pumping head rotates each barrel passes over the inlet and then the outlet ports of the pump. During the inlet cycle for each piston and barrel, oil is pumped into the barrel pushing the piston forward so that it always remains in contact with the swash plate. The stroke of each piston and volume of oil charged into its barrel is therefore dependent on the angle of the swash plate. After a piston and barrel has completed the inlet stroke, further rotation of the head aligns the barrel with the outlet port. Oil within the barrel is then forcibly ejected by the piston through the exhaust port to the hydraulic circuits.

9 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER Intake Filter 2. Oil Low Temperature Switch 3. Intake Filter Restriction Switch 4. Low Charge Pressure Switch 5. Charge Pressure By-Pass Valve 6. Steering Flow Control Valve CCLS Hydraulic Pump Installation 7. Steering and Low Pressure Circuit Pump 8. Charge Pressure Filter Dump Valve 9. Charge Pump 10. Charge Pressure Filter 11. Variable Flow Piston Pump 12. Load Sensing Valve (Flow and Pressure Compensating Valves) 5 The location of the principal components in the hydraulic pump assembly are identified above. These items are shown on the hydraulic circuit diagrams which describe the operating modes of the pump. The principal function of the valves and switches is as follows:- Intake Filter and Restriction Switch Oil for both the charge and steering pump is drawn from the rear axle centre housing via the intake filter. The filter incorporates a by-pass valve, which is an integral part of the replaceable filter and it is therefore essential that the correct filter is installed at every filter change. When the filter is blocked the oil filter restriction vacuum switch is activated and illuminates the oil filter restriction warning light on the instrument panel. Because oil is more viscous (thicker) when cold and can falsely indicate that the filter requires servicing a low temperature oil switch is also used in the filter restriction circuit. This switch ensures that the warning light will not operate if the oil temperature is less than 40 C. Low Charge Pressure Switch The low charge pressure switch will cause a light to Flash' on the instrument cluster whenever the charge pressure is less than 0.75bar (11 lbf/in 2 )

10 10 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 Charge Pressure Filter Dump Valve The charge pressure filter dump valve is a safety relief valve for relieving excess pressure on the charge pump should the filter be restricted. This valve will start to operate if the charge pressure exceeds bar ( lbf/in 2 ). It should be noted that the charge pressure filter does not incorporate a by-pass valve thus preventing dirty oil entering the variable flow pump circuits. 6 Charge Pressure Valve The charge pressure valve diverts excess oil supplied by the charge pump and not required by the variable flow piston pump to the inlet port of the steering and low pressure circuit pump. This valve starts to operate at a pressure of 1.6bar (23lbf/in 2 ) and when fully open limits the charge pressure circuit oil to 3.4bar (50lbf/in 2 ). 7 Steering Flow Control Valve (All Models except Supersteer) The steering flow control valve ensures that 25ltr/min (5.5 Imp Galls, 6.6 U.S. Galls/min) of oil is constantly supplied to the steering motor from the steering and low pressure circuit pump. All additional flow from the pump passes directly into the low pressure circuit. 8 Steering Flow Control Valve (Models with Supersteer) On tractors installed with supersteer front axles the steering flow control valve (2) is dynamically load sensed. When the steering wheel is turned slowly The dynamic load sensing line (3) supplies oil via the steering motor to the steering rams. When the steering wheel is turned quickly oil is also supplied to the steering circuit through the main supply feed (1) to the steering motor. All excess flow passes into the low pressure circuit (4). Refer to Steering Systems Section 41 for further details. 9

11 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER Plug and O' Ring 2. Housing 3. Flow Compensating Spool 4. Seat 5. Spring 6. Adjuster and O' Ring Seal 7. Locknut 8. Tamperproof Cap Flow and Pressure Compensating Valves 9. Tamperproof Cap 10. Locknut 11. Adjuster and O' Ring Seal 12. Spring 13. Seat 14. Pressure Compensator Spool 15. O' Ring Seals 16. Plug and O' Ring 10 Flow and Pressure Compensating Valves (CCLS Pump Load Sensing Valve) Output from the variable flow piston pump is determined by adjusting the angle of the swash plate in the pump. The flow compensating valves senses the circuit operating pressure and adjusts the swash plate angle to control pump output. If pump output and circuit pressure rises to 200bar (2900lbf/in 2 ) the pressure compensating valve overrides the flow compensating valve and adjusts the swash plate angle to limit maximum system pressure.

12 12 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 HYDRAULIC CIRCUIT OPERATION With Reference to Figure 10 The charge pressure pump draws oil through the charge pump inlet filter. Oil drawn by the charge pump flows through the charge pressure filter to the variable flow piston pump and also through the charge pressure valve to the inlet port of the steering pump. Because output from the charge pump can exceed the combined demand of the steering and variable displacement pumps an open gallery between the inlet side of the charge and steering pumps allows excess flow to the inlet side of the steering pump to be returned to the inlet side port of the charge pump. The variable flow closed centre load sensing hydraulic pump operates progressively in 4 modes:- Low Pressure Standby High Pressure Circuit Maximum Demand High Pressure Circuit Low Demand Maximum System Pressure (High Pressure Standby)

13 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER To High Pressure Circuit 2. From Compensating Valves 3. Intake Filter Restriction Switch 4. Intake Filter 5. Oil Low Temperature Switch 6. Low Charge Pressure Switch 7. Charge Pressure By-pass Valve 8. To Steering Circuit 9. Steering Flow Control Valve 10. To Low Pressure Circuit 11. Steering and Low Pressure Circuit Pump 12. Charge Pump 13. Charge Pressure Filter Dump Valve 14. Pump Intake 15. Charge Pressure Filter 16. Swash Plate 17. Variable Flow Piston Pump 18. Servo Piston Return Spring

14 14 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 Low Pressure Standby With Reference to Figure 11 Low pressure standby is the system pressure lbf/in 2 (21-24bar) maintained by the hydraulic pump when high pressure hydraulic circuits are not being operated. During engine start up, standby pressure has not been generated and both the flow and pressure compensating valves are held to the left by spring pressure. While the spools are held to the left oil pressure generated by the pump cannot be applied to the swash plate servo piston. The swash plate consequently remains in the maximum flow position until the pump has developed sufficient flow to produce pressure at low pressure standby. As pump output pressure increases to 21-24bar, this pressure is sensed in gallery E, Figure 11 and applied to the flow compensating spool. The spool gradually moves against the spring allowing oil flow from gallery E to gallery D. The controlled pressure rise in gallery D operates the swash plate servo piston, changing the angle of the swash plate in relation to the pumping head. The change in angle reduces the operating stroke of the pistons and output of the pump. As pump output decreases and the pressure in gallery D reduces to less than 350lbf/in 2 (24bar), the flow compensating valve gradually moves under spring pressure to the left bleeding gallery D to sump through gallery C. This reduces the control pressure applied to the servo piston, allowing the servo piston to retract at a controlled rate under pressure from the swash plate return spring and re-adjust the angle of the swash plate to increase pump output. This control process continues maintaining pump output pressure at bar (low pressure standby) until a high pressure circuit is operated and pump system pressure needs to be increased to operate the service.

15 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER High Pressure Circuit (In Neutral) 2. Pressure Compensating Valve 3. Flow Compensating Valve 4. Swash Plate

16 16 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 High Pressure Circuit High Demand High Pressure Circuit 2. Pressure Compensating Valve 3. Flow Compensating Valve 4. Swash Plate When the electronic draft control hydraulic lift, remote control valves or trailer braking system are operated the pressure rise in the hydraulic circuit is sensed by the load sensing line B. The pressure in the sensing line is now applied to the spring loaded end of the flow compensating valve. The combined pressure from the pilot line and flow compensating valve return spring causes the flow compensating spool to move against the standby pressure in gallery E, preventing the flow of oil to the swash plate servo piston through gallery C. The movement of the spool opens gallery D to the return to sump gallery C, allowing the servo piston to retract under pressure from the swash plate return spring and adjust the angle of the swash plate to increase pump output.

17 High Pressure Circuit Low Demand SECTION 35 - HYDRAULIC SYSTEM - CHAPTER High Pressure Circuit 2. Pressure Compensating Valve 3. Flow Compensating Valve 4. Swash Plate When output from the pump is meeting the demand of the hydraulic circuit the output pressure of the hydraulic pump in gallery E will continue to rise unless the flow from the pump is controlled. As pump pressure increases the differential between system pressure E and load sensed pressure B will similarly increase. When this differential rises towards 21bar (300lbf/in 2 ) the pressure in gallery E causes the flow compensator spool to move back against the spring and load sense pressure in Gallery B to open gallery E to gallery D. The controlled pressure rise in gallery D operates the swash plate servo piston and changes the swash plate angle to reduce pump output according to demand. It can now be seen that whenever the differential pressure between system and load sensed pressures approaches 21-24bar ( lbf/in 2 ) the flow compensator valve will operate to control the angle of the swash plate and consequently pump flow (output).

18 18 Controling Maximum System Pressure SECTION 35 - HYDRAULIC SYSTEM - CHAPTER High Pressure Circuit 2. Pressure Compensating Valve 3. Flow Compensating Valve 4. Swash Plate To limit the maximum output pressure of the piston pump and prevent consequential damage that may occur due to excessive pressures, a pressure compensating valve, located adjacent to the flow compensator valve, is incorporated in the swash plate control circuit. This valve limits the pressure to 190bar (2750lbf/in 2 ) and operates as follows:- As the pressure in gallery E increases to 2800lbf/in 2 (193bar) the pressure compensator valve spool (2) moves against the valve return spring and opens gallery E to gallery D. The pressure in gallery D is now applied to the servo piston which changes the swash plate angle to reduce pump output to minimum flow. This operating mode is referred to as high pressure standby.

19 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 19 Before commencing fault finding refer to the initial check fault finding chart which may identify an obvious cause for the concern and prevent unnecessary component disassembly. IMPORTANT: If the steering is inoperative, there will be no lubrication to the transmission or PTO clutch and the tractor must not be run for more than 5 minutes at a maximum engine speed of 1000rev/min. Fault finding charts listed in this Chapter are: FAULT FINDING Initial Fault Finding Check Transmission Low Pressure Warning Light On' Charge Pressure Light Flashing Intake Filter Restriction Warning Light On' Power Steering not Working or Working Incorrectly Trailer Brakes not Working Hydraulic Lift not Working Correctly Remote Control Valves not Working Initial Fault Finding Checks To be Performed Before Proceeding to General Diagnostic Procedure 1

20 20 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 1. Intake Filter 2. Oil Low Temperature Switch 3. Intake Filter Restriction Switch 4. Low Charge Pressure Switch 5. Charge Pressure By-Pass Valve 6. Steering Flow Control Valve 2 CCLS Hydraulic Pump Installation 7. Steering and Low Pressure Circuit Pump 8. Charge Pressure Filter Dump Valve 9. Charge Pump 10. Charge Pressure Filter 11. Variable Flow Piston Pump 12. Load Sensing Valve (Flow and Pressure Compensating Valves) TIA35004 Charge Pressure Filter Dump Valve TIA Steering Flow Control Valve 4

21 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 21 Transmission Low Pressure Warning Light ON'- Power Command Transmission Steering Pump Charge Pressure Valve 5 6 Transmission Low Oil Pressure Switch

22 22 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 Transmission Low Pressure Warning Light ON' - Range/Dual Command Transmissions Steering Pump Charge Pressure Valve 7 8 Transmission Low Oil Pressure Switch

23 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 23 Charge Pressure Light Flashing Intake Filter Restriction Warning Light On

24 24 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 Power Steering Not Working or Working Incorrectly Trailer Brakes Not Working

25 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 25 Hydraulic Lift Not Working Correctly

26 26 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 Remote Control Valves Not Working

27 PUMP PRESSURE AND FLOW TESTING SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 27 IMPORTANT: Before performing any pressure or flow testing operate the tractor until the oil in the rear axle is at normal operating temperature. 75 C (170 F). The following tests check operation of the hydraulic pump and associated high pressure circuits. Low Pressure Standby 1. Disconnect load sense line (1) to remote valves and install plug (2) Tool Number Install 0-42bar (0-600lbf/in 2 ) pressure gauge into lift port of remote valve number Set engine speed to 1500 rev/min. 4. Pull and hold remote valve control lever No 1 in the extend' position. 5. The pressure reading should be 21-24bar ( lbf/in 2 ) and is the Low Pressure Standby. 10 IMPORTANT: Do Not operate tractor brakes while remote valve No 1 lever is in operating position, otherwise the system pressure will increase to maximum pressure of 200bar (2900lbf/in 2 ) resulting in damage to the pressure gauge. If pressure reading is marginally away from Specification adjust flow compensating valve. If reading is high examine flow compensating valve (1) spool for sticking. 6. Reconnect load sense line

28 28 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 High Pressure Standby 1. Install 0-420bar (0-6000lbf/in 2 ) pressure gauge into lift port of remote valve number Set engine speed to 1500 rev/min Pull and hold remote valve control lever No 1 in the extend' position. 4. The pressure reading should rise to be 200bar (2900lbf/in 2 ). and is the High Pressure Standby If reading is not to specification adjust pressure compensating valve (2). 15

29 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 29 Load Sensing Circuit Test This test checks that the load sense lines which signal the hydraulic pump to go on and off load are functioning. 1. Install Tee adaptor (3) and quick release adaptor (2) into load sense line between compensating valves and trailer brake valve. 2. Connect 0-420bar (0-6000lbf/in 2 ) pressure gauge using quick release coupler Set engine speed to 1500rev/min. 4. Operate in turn each of the high pressure hydraulic services (Remote Valves, Trailer Brakes, Hydraulic lift). As each service is operated the pressure should rise from 21-24bar ( lbf/in 2 ) to a maximum of 190bar (2750lbf/in 2 ). Changes in pressure indicate that the load sensing line to each service is operating. 16 Charge Pressure Test 1. Remove charge pressure switch. 2. Install 0-10bar (0-100lbf/in 2 ) pressure gauge (1) using adaptors (2) as listed below. adaptor quick release adaptor quick release coupler or M10x1.0 7/16 JIC adaptor NOTE: The thread size of the charge pressure switch port is M10x1 DIN specification Install flow meter between remote valves I and II. Ensure inlet hose of flowmeter is installed into extend port of valve No I. 4. Fully open load valve on flow meter. 5. Set remote valve flow control knobs to maximum flow. 19

30 30 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 6. Set remote valve No 2 in Float' position. 7. Set remote valve No 1 in Extend' position. 8. Start tractor and set engine speed to 1500rev/min Move control lever for remote valve No 1 between extend and neutral position. The charge pressure readings should not vary outside bar (23-50lbf/in 2 ). If pressure readings below 1.6bar (23lbf/in 2 ) are recorded replace hydraulic filters and re test. If after retest charge pressure is still below specification examine both the charge pressure filter dump valve and charge pressure valve before disassembling pump to inspect for wear. 21 Variable Flow Piston Pump Flow Test To flow test the variable flow piston pump it is recommended that the output is checked at the remote valves. 1. Install flow meter between inlet ports of remote valves I and II. 2. Set flow control knobs to maximum flow Ensure load valve on flow meter is fully Open'. 4. Set tractor engine speed to 1100 rev/min. 5. Set remote valve No 2 in Float' position and remote valve No 1 in Extend' position. 23

31 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER Adjust load on flow meter to a of pressure of 100bar. 7. If a flow of 45 ltr/min is recorded the pump flow is to specification. NOTE: This test is performed at half maximum rated speed and assumes that pump flow at rated speed is twice that measured in the test. Steering Pump/Low Pressure Pump Test There is no relief valve in the steering/low pressure circuit pump. The following practical test will determine if steering pump output is sufficient to allow satisfactory operation of the steering system. 24 Steering Test 1. Set engine speed to 1100 rev/min. 2. Turn steering quickly from lock to lock. If steering is operating correctly the reaction should be immediate with no time delay between turning the steering wheel and movement of the wheels. 3. At full lock the relief valve in the steering motor should be heard to blow and the engine speed drop to approximately 970rev/min. 1 If transmission low pressure warning light comes on when the steering is held on full lock this is an indication that the pump has developed an internal leak. Check torque of pump mounting bolts and if tight examine pump for leaking seals or wear. 25 Steering Circuit Pressure Test 1. Install Tee adaptor (2) and quick release adaptor (3) into hose to steering cylinder. 2. Connect bar ( Connect 0-420bar (0-6000lbf/in 2 ) pressure gauge (1) using quick release coupler Set engine speed to 1500rev/min. 5. Turn steering wheel to full lock and hold in position. 6. Pressure reading of 190 bar should be recorded. 26

32 32 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 Hydraulic Pump Leak Test The hydraulic pump leak test should be performed whenever operation of the hydraulic system is erratic or the pump is extremely noisy. The purpose of the test is to, ascertain if the malfunction of the system is due to an internal pump leak or alternatively the ingress of air due to a leak through a component in the system. 1. Disconnect the breather tube (1) from the top of the hydraulic lift cover (2) Attach approximately 1 1 / 2 metres of clear plastic tubing (1) to the breather connection (2) on top of the transmission and position the tubing so that it forms a U' (Similar to a manometer). 3. Fill the tube with sufficient oil to prevent the ingress of air through the tube. 4. Set tractor engine speed to 1000 rev/min and pull and hold remote valve lever If the hydraulic pump has an internal leak oil or bubbles will sucked from the plastic tube into the transmission. If the hydraulic circuit has an external leak the oil in the U' of the plastic tube will be pushed towards the open end of the tube by the air being drawn into the transmission casing through the pump. 28 WARNING If the leak is excessively large it is possible for the oil to be projected out of the tube. Take care to position the tube so not to cause injury or project oil into the work area. If an external leak is diagnosed use an oil can' to selectively apply a film of oil around the joints of the circuit. For example remote valve tubing joints. When oil is applied to the leaking joint the noise in the pump will cease. If an internal leak is identified inspect mounting face at pump intake port or intake tube in transmission for missing or damaged O' ring, Figure

33 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 33 OVERHAUL CCLS Hydraulic Pump Installation 1 1. Intake Filter 2. Oil Low Temperature Switch 3. Intake Filter Restriction Switch 4. Low Charge Pressure Switch 5. Charge Pressure By-Pass Valve 6. Steering Flow Control Valve 7. Steering and Low Pressure Circuit Pump 8. Charge Pressure Filter Dump Valve 9. Charge Pump 10. Charge Pressure Filter 11. Variable Flow Piston Pump 12. Load Sensing Valve (Flow and Pressure Compensating Valves) This procedure describes the overhaul of the complete pump assembly when removed from the tractor. The following items however can be serviced with the pump installed on the tractor. Charge Pressure Valve Charge Pressure Filter Dump Valve Low Charge Pressure Switch Steering Flow Control Valve Pressure and Flow Compensating Valves Steering Pump Assembly

34 34 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 Charge Pressure Valve 1. Remove charge pressure valve manifold from steering pump Remove circlip (2) and using New Holland Tool No unscrew valve (3) from manifold (1). NOTE: If during pressure testing the charge pressure reading is away from specified value of bar (23-50lbf/in 2 ) both the charge pressure valve and charge pressure filter dump valve must be examined for faulty operation. Do Not attempt to adjust the valves which is supplied as a pre-set assemblies and should not be adjusted. 3 Charge Pressure Filter Dump Valve 1. Remove Plug (1) and O ring (2). 2. Using New Holland Tool No unscrew valve (3) from pump body. 4 Steering Flow Control Valve 1. Unscrew plugs (1) and (4) and remove spring (3) and spool (2). 2. Inspect spool for wear or damage. If damaged it is necessary to replace both spool and steering pump end plate. 3. Lubricate spool with clean hydraulic oil prior to reassembly. 5

35 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 35 Pressure and Flow Compensator Valve 1. Disconnect load sense line connection and remove pressure and flow compensating valve assembly. 2. Remove the tamper proof caps, carefully unscrew each adjuster and remove the component parts. 3. To ensure correct re-assembly keep the component parts for each valve separate. NOTE: The stem on the flow compensating spool is longer than that on the pressure compensating spool. IMPORTANT: Due to extreme spring pressure within valves DO NOT remove rear plugs until the adjusters have been removed. 6 Flow and Pressure Compensating Valves 7 1. Plug and O' Ring 2. Housing 3. Flow Compensating Spool 4. Seat 5. Spring 6. Adjuster and O' Ring Seal 7. Locknut 8. Tamperproof Cap 9. Tamperproof Cap 10. Locknut 11. Adjuster and O' Ring Seal 12. Spring 13. Seat 14. Pressure Compensator Spool 15. O' Ring Seals 16. Plug and O' Ring

36 36 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 Re-assembly of the valves follows the removal procedure in reverse. On re-assembly observe the following:- Wash all components in a suitable solvent. Examine all components for wear or damage. If the spools are damaged it is necessary to replace the complete valve assembly. Lubricate all parts with clean hydraulic oil. To aid re-assembly of pressure and flow compensating valves, the spools should be inserted into the rear of the housing. 8 Tighten all plugs and locknuts to the correct torque as detailed in Specifications. When installing valve on pump ensure all O' ring seals are correctly installed. Pressure test the pump and adjust the pressure and flow compensating valves to the correct specification as detailed in Pressure Testing Section of this Chapter. 9

37 PUMP REMOVAL SECTION 35 - HYDRAULIC SYSTEM - CHAPTER Securely support the tractor on suitable axle stands and remove the right hand rear wheel. 2. Remove oil filters. NOTE: To prevent excessive loss of oil loosen intake filter by approximately one turn and leave for one minute to allow oil in filter to drain into sump Disconnect all electrical and hydraulic connections to pump. 4. Ensure lubrication pipe banjo connector (1) and brake line retaining bracket (2) are disconnected from pump body Where fitted, remove ground speed PTO interlock safety switch and bracket from pump mounting boss Manufacture from M12x1.25 bolts two alignment dowels to assist in removing/ installing pump on tractor. Cut a screwdriver slot across the end face of each dowel. 13

38 38 SECTION 35 - HYDRAULIC SYSTEM - CHAPTER 2 7. Remove upper pump retaining bolts and install the two locally manufactured alignment dowels Remove three lower retaining bolts Locate suport tool onto pump and using tractor splitting kit MS 2700C remove pump from tractor. Alternatively use the New Holland support tool (1) and use suitable trolley jack to remove pump, Figure. WARNING The hydraulic pump is a heavy component and weighs 40kgf. It is important that it is securely supported when being removed from the tractor. 16 NOTE: Use a drip tray to collect the small volume of oil that may be lost from the transmission during removal of the pump. 17

39 INSTALLATION SECTION 35 - HYDRAULIC SYSTEM - CHAPTER Ensure O' ring (1) is correctly positioned around drive gear retaining pin and pump alignment dowels are not damaged. Two different types of dowel installation are used, either solid dowels as shown or ring dowels located around top and bottom pump mounting bolts. If dowels are damaged always replace with the same type as originally installed on the tractor. 2. Clean mating face of pump and transmission and apply New Holland sealer to transmission face Ensure alignment dowels are installed. The use of the alignment dowels is an important requirement when positioning the pump onto the transmission housing Install pump using the removal procedure in reverse. 5. After installation ensure pump retaining bolts are tightened to a torque of 76-90Nm (56-66lbfft). 21