Basics of Service – HYDROSTATIC POWER STEERING HYDROSTATIC POWER STEERING SYSTEM – FT & PT 1. DESCRIPTION AND OPERATION Farmtrac & Powertrac feature an hydraulic power assisted, hydrostatic steering system. The components are serviced separately and consist of the steering column shaft, steering moto r, front steering cylinder, power steering pump, oil cover and reservoir, and the hoses and tubes required to connect the system. The integral power steering pump is mounted on the rear of the engine front cover plate at the left hand side of the engine. The pump is connected to the steering motor by two oil tubes. The transmission oil is used to feed the oil requirement of steering system. The steering wheel is secured to the steering column shaft. The steering column upper shaft is joined to the power steering motor input shaft by a coupling secured with a pinch bolt. The power steering motor and steering column assembly are mounted on a housing bracket which is bolt at the clutch housing. The hydrostatic steering motor uses a linear control valve to control the direction of the steered wheels and metering unit to control the rate of turn. In the event of pump failure the metering unit functions as an hydraulic pump and the wheels can be turned manually. 1.1 STEERING CYLINDER The double acting steering cylinder is transversely mounted on the front axle. The cylinder end of the assembly is bolted to an adjuster bar which forms an integral part of the front axle assembly and facilitialies re-positioning of the cylinder when adjusting the track setting. The rod end is attached to the left-hand spindle arm which is connected by the track rod to the right-hand spindle arm. The cylinder incorporates a piston centrally mounted on the piston rod. This arrangement enables the piston to prevent surfaces of equal area to the operating oil and the resultant forces ensure similar right and left-hand turning circles.

EIFM – Pub1.0/ April”07

1.Anchor 2.Cylinder assy. Retaining nut 3.Feed hose support bracket 4.Rod end assembly.

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Basics of Service – HYDROSTATIC POWER STEERING

1.2 EXPLODED VIEW

1. Dust seal ring, 2. Housing, spool and sleeve. Check valve and the seats for relief and shock valves are locktited, 3. Ball ? 8,5 mm, 4. Thread bushing, 5. Oring used with kin-ring (item 6), 6. O-ring, 7. Bearing assembly, 10. Ring, 11. Cross pin, 12. Set of springs, 13.Cardan shaft, 14. Spacer, 15. O-ring,16. Distributor plate, 17. Gearwheel set, 18. O-ring, 19. End cover, 20. Washer, 22. Special screw, 23. Screw, 24. Name plate, 30. Complete relief valve, 31. Spring wire, 32. Complete shock valve, 33. Ball ? ? 3/16 in, 34. Rolled pin, 35. Bushing, 36. Ball, 38. Spring, 39&40. O-ring.

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Basics of Service – HYDROSTATIC POWER STEERING 1.2.1 HYDROSTATIC STEERING MOTOR – OVERHAUL A. REMOVAL 1. Disconnect the battery ground cable at the battery. 2. Clean the flexible steering hose to rigid type connections. 3. With a suitable container to store the escaping steering oil, mark and separate the flexible steering hoses from the rigid pipes. Cap and seal the pipes, using suitable plugs. 4. Slacken the retainer bolts securing the pipes to the side of the engine. 5. Unclip the separate the thro ttle screws and remove the lower steering column shroud by withdrawing main harness connector to gain access to the steering column to motor coupling. 6. Remove the four bolts retaining the steering motor support bracket. 7. Slacken clamp bolts securing the steering column to the motor and carefully withdraw the motor assembly from the left-hand side of the tractor. B. DISASSEMBLY •

Cleanliness in servicing the power steering system is imperative. If it is necessary to disassemble and of the units, ensure a clean work bench or table is used.

•

Clean off external dirt before the unit is placed on the work bench.

•

When disassembled, parts should be cleaned only in clear-clean petroleum base solvent and blown dry with clean air. Other solvents may cause deterioration of rubber seals. Avoid wiping parts with cloth and never steam clean hydraulic steering assemblies.

NOTE : The spool and housing, the commutator and commutator ring the rotor and stator are selectively fitted and must be services as follows : •

If the spool or housing must be replaced, replace the complete motor.

•

If the commutator or commutator ring must be replaced, replace both as a matched set.

•

If the rotor or stator must be replaced, replace the complete metering element.

•

If the pin in the end cover or the end cover must be replaced, replace the pin and end cover assembly.

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Basics of Service – HYDROSTATIC POWER STEERING

1.2.2 DISMANTLING

1. Dismantle steering column from steering unit and place the steering unit in the holding tool. Screw out the screws in the end cover (6-off plus one special screw ).

2. Remove the end cover, sideways.

3. Lift the gearwheel set (with spacer if fitted) off the unit. Take out the two o-rings.

4. Remove cardan shaft.

5. Remove distributor plate.

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Basics of Service – HYDROSTATIC POWER STEERING

6. Screw out the threaded bush over the check valve.

7. Remove o-ring.

8. Shake out the check valve ball and suction valve pins and balls.

9. Take care to keep the cross pin in the sleeve and spool horizontal. The pin can be seen through the open end of the spool. Press the spool inwards and the sleeve, ring, bearing races and needle bearing will be pushed out of the housing together.

10.Take ring, bearing races and needle bearing from sleeve and spool. The outer (thin) bearing race can sometimes “stick” in the housing, therefore check that it has come out.

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Basics of Service – HYDROSTATIC POWER STEERING

11.Press out the cross pin. Use the special screw from the end cover.

12.A small mark has been made with a pumice stone on both spool and sleeve close to one of the slots for the neutral position springs (see drawing). If the mark is not visible, remember to leave a mark of your own on sleeve and spool before the neutral position springs are dismantled.

13.Carefully press the spool out of the sleeve.

14.Press the neutral position springs out of their slots in the spool.

15.Remove dust seal and o-ring.

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Basics of Service – HYDROSTATIC POWER STEERING

16.Remove plugs from shock valves using a 6 mm hexagon socket spanner.

17.Remove seal washers (2-off).

18.Unscrew the setting screws using a 6 mm hexagon socket spanner.

19.Shake out the two springs and two valve balls into your hand. The valve seats are bonded into the housing and cannot be removed.

20.Screw out the plug using and 8 mm hexagon socket spanner. Remove seal washers.

EIFM – Pub1.0/ April”07

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Basics of Service – HYDROSTATIC POWER STEERING

21.Unscrew the setting screw using an 8 mm hexagon socket spanner.

22.Shake out spring and piston. The valve seat is bonded into the housing and cannot be removed.

23.The steering units now completely dismantled. Replace these pins prior to the reassembly! Cleaning Clean all parts carefully in Shellsol K or the like. Inspection and replacement Replace all seals and washers. Check all parts carefully and make any replacements necessary. Lubrication Before assembly, lubricate all parts with hydraulic oil.

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Basics of Service – HYDROSTATIC POWER STEERING

1.3 ASSEMBLING

1. Place the two flat neutral position springs in the slot. Place the curved springs between the flat ones and press them into place.

2. Line up the spring set.

3. Guide the spool into the sleeve.

4. Assemble spool and sleeve. Note: When assembling spool and sleeve only one of two possible ways of positioning the spring slots is correct. There are three slots in the spool and three holes in the sleeve in the end of the spool/sleeve opposite to the end with spring slots. Place the slots and holes opposite each other so that parts of the holes in the sleeve are visible through the slots in the spool.

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Basics of Service – HYDROSTATIC POWER STEERING

5. Press the springs together and push the neutral position springs into place in the sleeve.

6. Line up the springs and centre them.

7. Guide the ring down over the sleeve. Note: The ring should be able to move - free of the springs.

8. Fit the cross pin into the spool/sleeve.

9. Fit bearing races and needle bearing as shown on below drawing.

1 2 3 4 5

Outer bearing race Needle bearing Inner bearing race Spool Sleeve

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Basics of Service – HYDROSTATIC POWER STEERING Installation instructions for o-ring

10.Turn the steering unit until the bore is horizontal. Guide the outer part of the assembly tool into the bore for the spool/sleeve.

11.Grease o-ring and king-ring with hydraulic oil and place them on the tool.

12.Hold the outer part of the assembly tool in the bottom of the steering unit housing and guide the inner part of the tool right to the bottom.

13.Press and turn the o-ring into position in the housing.

14.Draw the inner and outer parts of the assembly tool out of the steering unit bore, leaving the guide from the inner part in the bore.

15.Lubricate the lip seal with hydraulic oil and place it on the assembly tool.

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Basics of Service – HYDROSTATIC POWER STEERING

16.Guide the assembly tool right to the bottom.

17.Press and turn the lip seal into place in the housing.

18.With a light turning movement, guide the spool and sleeve into the bore. Note: Fit the spool set holding the cross pin horizontal.

19.The spool set will push out the assembly tool guide. The o-ring is now in position.

20.Turn the steering unit until the bore is vertical again. Put the check valve ball into the hole indicated by the arrow.

21.Screw the threaded bush lightly into the check valve bore. The top of the bush must lie just below the surface of the housing.

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Basics of Service – HYDROSTATIC POWER STEERING

22.Place a ball in the two holes indicated by the arrows.

23.Place a new pin in the same two holes.

24.Grease the o-ring with mineral oil approx. viscosity 500 mm2/s at 20°C.

25.Place the distributor plate so that the channel holes match the holes in the housing.

26.Guide the cardan shaft down into the bore so that the slot is parallel with the connection flange.

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Basics of Service – HYDROSTATIC POWER STEERING

27.Place the cardan shaft as shown so that it is held in position by the mounting fork.

28.Grease the two o-rings with mineral oil approx. viscosity 500 mm2/s at 20°C and place them in the two grooves in the gear rim. Fit the gearwheel and rim on the cardan shaft.

Important: Fit the gearwheel (rotor) and cardan shaft so that a tooth base in the rotor is positioned in relation to the shaft slot as shown. Turn the gear rim so that the seven trough holes match the holes in the housing.

29.Place the end cover in position.

30.Fit the special screw with washer and place it in the hole shown.

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Basics of Service – HYDROSTATIC POWER STEERING

31.Fit the six screws with washers and insert them. Cross-tighten all the screws and the rolled pin with a torque of 3.0 +/-0.6 Kgm.

Assembly of the pressure relief valve

32.Fit the piston.

33.Fit the spring.

34.Screw in the setting screw with an 8 mm hexagon socket spanner. Make the pressure setting on a panel or the vehicle.

Assembly of the shock valves

35.Put a ball in the two holes indicated by the arrows.

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Basics of Service – HYDROSTATIC POWER STEERING

36.Place springs and valve cones over the two balls. Note: The blue spring applies to setting range 90-180 bar. The untreated spring applies to setting range 170-260 bar.

37.Screw in the two setting screws using a 6 mm hexagon socket spanner. Make the pressure setting on a panel or the vehicle.

38.Screw in the two setting screws using a 6 mm hexagon socket spanner. Make the pressure setting on a panel or the vehicle.

39.Place the dust seal ring in the housing. With the dust seal ring must be placed only after the pressure relief valve and shock valves have been fitted.

40.Fit the dust seal ring in the housing using special tool SJ 150-9000-22 and a plastic hammer.

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Basics of Service – HYDROSTATIC POWER STEERING

2. Max. tightening torque and hydraulic connections

Screwed connection

Max. Tightening torque. Kgm With cutting edge

With copper washer

With aluminium washer

G 1/4

4

2

3

G 3/8

6

2

5

G 1/2

10

3

8

7/16-20 UNF

2

3/4-16 UNF

6

With Oring

M 12 x 1,5

4

2

3

2

M 18 x 1,5)

7

2

5

5

M 22 x 1,5

10

3

8

7

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Basics of Service – HYDROSTATIC POWER STEERING 3. TROUBLE SHOOTING Fault Possible cause 1. No or insufficient supply to pump.

Remedy oil

2. Viscosity of oil too high.

1. Pump noisy

2. No pressure

3. No or unstable pressure

4. Noise in the relief valve 5. Air in the system, foam in the oil

1. Clean suction filter. Check that no damage or narrowing is to be found on suction line. 2. Change the oil, adjust viscosity to working temperature.

3. Pump takes in air: a) at the pump shaft b) at loose or damaged suction line c) oil level too low d) oil takes in air in the tank(return pipe discharging over oil surface)

3. Replace shaft seal. Tighten fittings or replace suction line. Refill with clean oil. Extend return pipe to 54 cm under the surface and as far as possible from the suction pipe.

4. Pump worn out.

4. Repair or replace pump.

5. R.P.M. too high.

5. Adjust the R.P.M.

6. Oil pressure too high.

6. Adjust oil pressure.

1. Oil level too low.

1. Refill with clean oil.

2. Pump does not run or runs in the wrong direction.

2. Adjust direction of rotation. Check driving belt or coupling.

3. Relief valve is stuck in open position.

3. Repair relief valve.

4. Pump defective, broken shaft or key for rotor.

4. Repair pump.

1. Working pressure too low.

1. Check valve.

2. Leaky pressure adjusting valve or pilot valve.

2. Repair valve.

3. The oil flows more or less to the tank through defective valve or cylinder.

3. Repair cylinder or valve.

1. Excessive flow.

1. Fit a larger valve corresponding to the actual oil volume.

2. Dirt or chips between valve cone and valve seat.

2. Repair valve.

1. Leaky suction line.

1. Retighten or replace line.

2. Excessive resistance in suction line.

2. Clean filter and suction line, or replace with pipes having larger bores. Check fittings.

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pressure

adjusting

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Basics of Service – HYDROSTATIC POWER STEERING

Fault

Possible cause

Remedy

5. Air in the system, foam in the oil

3. Return line discharges above the oil level - could cause foam formation.

3. Remove return line from suction line and extend if necessary. 4. Change over to correct oil type.

4. Incorrect oil type. 1. No water.

6. Overheat ed system

supply

of

cooling

1. Re-establish supply of cooling water.

2. Oil cooler blocked or dirty.

2. Clean oil cooler.

3. Excessive oil viscosity.

3. Change over to correct oil type.

4. Abnormal internal leakage in one or more components.

4. Repair or replace defective components.

1) No or insufficient oil pressure a) Pump does not run b) Pump defective c) Pump runs in the wrong direction d) Pump is worn out e) Pump is under dimensioned

a. Start up pump (loose V-belt) b. Repair or replace pump c. Correct direction of rotation of pump or replace pump d. Replace pump e. Install a larger pump (examine pressure need and flow)

2) Pressure relief valve is 2) Replace or clean pressure stuck in open position or relief valve. Adjust the valve to setting pressure is too low. the correct pressure. 7. Steering 3) Repair or clean the priority wheel is 3) Priority valve is stuck in valve. heavy to open position. turn 4) Lubricate bearings and joints 4) Too much friction in the of steering gear or repair if mechanical pans of the necessary. Check steering vehicle. column installation. 5) Emergency steering balls missing.

5) Install new balls.

6) Combination: Downstream 6) Change cylinder type (through system + steering unit with going piston rod). If necessary suction valve and differential use two differential cylinders. cylinder are inexpedient.

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Basics of Service – HYDROSTATIC POWER STEERING

Fault

Possible cause

Remedy

8. Regular adjustmen ts of the steering wheel are necessary ("Snakelike driving")

1. Leaf spring without spring 1. Replace leaf springs. force or broken.

9. Neutral position of steering wheel cannot be obtained, i.e. there is a tendency towards "motoring"

1. Steering column and 1. Align the steering column steering unit out of line. with steering unit.

10."Motoring" effect. The steering wheel can turn on its own.

11.Backlash.

12."Shimmy"effect. The steered wheels vibrate. (Rough tread on tyres gives vibrations)

2. Spring in double shock 2. Replace shock valve. valve broken. 3. Gear wheel set worn.

3. Replace gear wheel set.

4. Cylinder seized or piston seals worn.

4. Replace defective parts.

2. Too Little or no play 2. Adjust the play and, if between steering column necessary, shorten the splines and steering unit input shaft. journal. 3. Pinching between inner 3. Contact the nearest service and outer spools. shop. 1) Leaf springs are stuck or broken and have therefore 1) Replace leaf springs. reduced spring force. 2) Clean steering unit or 2) Inner and outer spools contact the nearest service pinch, possibly due to dirt. shop. 3) Return pressure in 3) Reduce return pressure, connection with the reaction change cylinder type or use a between differentia l cylinder non-reaction control unit. and steering unit too high. 1) Cardan shaft fork worn or broken.

1) Replace cardan shaft.

2) Leaf springs without spring force or broken.

2) Replace leaf springs.

3) Worn splines on the steering column.

3) Replace steering column.

1) Air in the steering cylinder.

1) Bleed cylinder. Find and remove the reason for air collection.

2) Mechanical connections or 2) Replace worn parts. wheel bearings worn.

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Basics of Service – HYDROSTATIC POWER STEERING

Fault

Possible cause

Remedy

13.Steering wheel can be turned the whole time without the steered wheels moving.

1) Oil is needed in the tank.

1) Fill with clean oil and bleed the system.

2) Steering cylinder worn.

2) Replace or repair cylinder.

3) Gear wheel set worn.

3) Replace gear wheel set.

4) Spacer across cardan shaft forgotten.

4) Install spacer.

14.Steering wheel can be turned slowly in one or both directions without the steered Wheels turning.

1) One or both anti-cavitation 1) Clean or replace defect or valves are leaky or are missing valves. missing in steering unit.

2) One or both shock valves 2) Clean or replace defective are leaky or are missing in or missing valves. steering unit.

1) Insufficient oil supply to steering unit, pump defective 1) Replace pump or increase or number of revolutions too number of revolutions. low. 15.Steering is too slow and heavy when trying to turn quickly.

2) Relief valve setting too 2) Adjust valve to correct low. setting. 3) Relief valve sticking owing 3) Clean the valve. to dirt. 4) Clean the valve. that spool moves without spring. 5) Replace spring 5) Too weak spring in priority stronger (There are 3 valve. 4, 7&10 bar). 4) Spool in priority sticking owing to dirt.

valve

check easily by a sizes:

16."Kick-back" in steering wheel from system. Kicks from wheels.

1) Fault in the system.

1) Contact Danfoss.

17.Heavy kickback in steering wheel in both directions.

1) Wrong setting of cardan shaft and gear wheel set.

1) Correct setting as shown in Service Manual.

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Basics of Service – HYDROSTATIC POWER STEERING

Fault 18.Turning the steering wheel activates the steered wheels opposite.

19.Hard point when starting to turn the steering wheel.

20.Too little steering force (possibly to one side only).

21.Leakage at either input shaft, end cover, gearwheel set, housing or top part.

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Possible cause

Remedy

1) Hydraulic hoses for the steering cylinders have been 1) Reverse the hoses. switched around.

1) Spring force in priority valve too weak.

1) Replace spring by a stronger (4, 7 and 10 bar).

2) Air in LS and /or PP pipes.

2) Bleed LS and PP pipes.

3) Clogged orifices in LS or PP side priority valve.

3) Clean orifices in spool and in connecting plugs for LS and PP.

4) Oil is too thick (cold).

4) Let motor run until oil is warm.

1) Pump pressure too low.

1) Correct pump pressure.

2) Too little steering cylinder.

2) Fit a larger cylinder.

3) Piston rod area of the 3) Fit cylinder with thinner differential cylinder too large piston rod or 2 differential compared with piston cylinders. diameter. 1) Shaft defective

1) Replace shaft seal.

2) Screws loose.

2) Tighten screws Torque 33,5 Kgm or steering unit (2,53 Kgm).

3) Washers or O-rings defective.

3) Replace washers and Orings.

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