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Fiat Tractor 55-60 60-90 79-90 80-90 90-90 100-90 tractor factory workshop manual download

Quick overview (what, why, and basic theory)
- What this is: Fiat 55–60 → 100–90 tractors use a hydraulic assisted steering system: the driver turns the wheel, a steering control valve directs hydraulic pressure from a power pump to assist a mechanical steering gearbox or steering ram so you don’t have to muscle the wheels. The system’s main job is to reduce steering effort and control wheel motion precisely.
- Why repair is needed: common failures are leaks, worn mechanical parts (play in box/linkage), worn pump or control valve (poor assistance, noise), contaminated fluid (sluggish response, damage), air in the system (spongy steering), or failed seals in cylinders/box (drift or loss of assist).
- How it works (analogy): Think of the system like the human arm with power assist. The steering wheel is your brain telling the arm which way to move. The hydraulic pump is the heart, pushing “blood” (hydraulic oil) around. The steering valve is the nervous system that routes fluid to the correct side of the “muscle” (steering cylinder or gearbox ram). The cylinder/gearbox actually moves the wheels — like muscles contracting. Relief/limit valves are safety features that prevent too much pressure (like bones that stop over-extension).

Main components (detailed)
- Power steering pump: engine-driven gear/gerotor pump mounted on the engine. Purpose: generate flow/pressure. Has pressure outlet and return port; often contains an internal or external relief valve. Typical failure: worn internal gears, noisy whining, low flow.
- Reservoir: holds hydraulic oil, often integral to pump or separate. Has fill/level cap and sometimes a screen. Purpose: store oil and let air/bubbles separate.
- Pressure hose (high-pressure): reinforced hose from pump outlet to steering control valve or steering box; carries high-pressure oil. Failure: external leak, burst, internal collapse.
- Return hose (low-pressure): carries oil back to reservoir. Often braided rubber. Failure: leaks, clogging.
- Steering control valve (orbital/orbital valve or rotary valve): converts rotary motion of steering column into direction-controlled flow. Mounted on or near the steering box or integrated in the box. Contains spools and ports. Failure: internal wear → incorrect flow, drifting, poor centering.
- Steering gearbox (hydrostatic assist box or power steering box): contains worm/sector or similar mechanical reduction plus hydraulic assist channels. Converts rotary motion to lateral movement of the pitman/drag link. Wear causes play and free movement.
- Steering cylinder/ram (if used): a double-acting cylinder which moves tie rods/axle; has seals and rod. Failure: leaking seals → loss of assist and fluid.
- Drag link, tie rods, pitman arm, kingpins, wheel bearings: mechanical linkage components. Wear here shows as play even if hydraulics OK.
- Relief valve/pressure regulator: limits maximum system pressure to protect components.
- Filters/strainers: inline mesh or cartridge to keep contamination out.
- Fittings/adapters and check valves: connect hoses and control flow direction.

Symptoms and probable causes (quick map)
- Heavy steering at low RPM: low pump flow (worn pump, belt slip), clogged strainer, low engine RPM, or worn control valve.
- Whining/groaning noise from pump: low fluid, aeration, worn pump, belt slip.
- Steering very light / no return to center / wanders: internal leak in control valve, worn steering box, worn cylinder seals.
- Steering drifts or holds position after letting go: control valve leaking internally or worn cylinder seals.
- Visible leaks, puddles of oil: hose/fitting, pump seal, cylinder rod seal, steering box gasket.
- Excessive play in wheel (free play before wheels move): worn steering gearbox, worn drag link/tie-rod ends, loose pitman arm.
- Front wheel binds one way or another: mechanical binding (tie rod/kingpin) or hydraulic blockage.

Tools, parts & shop supplies you’ll need
- Tools: metric socket set, wrenches, screwdrivers, line wrenches, torque wrench, pry bars, hammer, punch, puller (pitman arm/pullers), bench vice, hydraulic press (for rebuilds), snap-ring pliers, seal drivers, soft mallet, feeler gauges.
- Specialty: hydraulic pressure gauge + adapters (for pump test), oil catch pan, hose clamps, crimp tool / replacement hoses or adapters, thread sealant rated for hydraulics, replacement seals/kits, replacement pump or steering box (or complete overhaul kit), shop rags, parts cleaner, safety glasses and gloves.
- Fluids: correct grade hydraulic oil for Fiat tractors (consult service manual — typically tractor hydraulic oil/Hydraulic oil ISO 46/68 depending on climate; use what manual specifies), clean reservoir/strainer if contaminated.
- Safety gear: wheel chocks, jack stands, blocking to support front axle, PPE.

Safety first (always)
- Lower implement, park on level ground, engage parking brake, chock rear wheels. Do not rely on a jack alone — always use stands.
- Relieve hydraulic pressure before disconnecting hoses: slow engine to idle, cycle steering slowly, then shut engine and center wheels. Wrap rags around fittings and wear eye protection — pressurized oil can penetrate skin.
- Clean around fittings before opening to avoid dirt ingress.
- Cap and plug hoses and ports immediately to keep contamination out.

Diagnostic steps (start here)
1. Visual inspection: check fluid level, color and smell (burned), check hoses and fittings for leaks, check belt tension on pump, check reservoir strainer.
2. Check mechanical linkages: jack front end, support on stands, wiggle wheels and draglink/pitman/tie rods to assess play. If mechanical play exists, fix that first.
3. Check for air and contamination: milky/foamy oil → air; dark grit-heavy oil → contamination.
4. Pump pressure test: attach pressure gauge to pump outlet (use appropriate adapter). Compare pressure to service spec (consult manual). Low pressure → worn pump or relief valve stuck open; very high pressure → relief valve stuck closed or blockage.
5. Flow test or valve test: observe cylinder movement when steering wheel is turned; if unit doesn’t move with pressure present, control valve or steering box is at fault.
6. Listening: groan means cavitation or aeration; metallic grinding means internal pump wear.

Common repairs and step-by-step procedures

A. Replace/repair power steering pump (typical)
When to do: pump noisy, low pressure, contaminated internals, leaking pump shaft.
Steps:
1. Prepare: park, chock, lower implement, remove battery negative for safety if wiring nearby.
2. Drain: place catch pan under reservoir/pump. Loosen return line to drain reservoir and pump; cap/plug lines and ports.
3. Remove belt: loosen alternator/idler to remove V-belt that drives pump.
4. Label and disconnect hoses: mark pressure and return hoses so you reconnect correctly. Use line wrenches to avoid rounding fittings. Immediately cap fittings to prevent contamination.
5. Unbolt pump: remove mounting bolts and any brackets. Note spacer/shims; keep hardware together.
6. Bench work: transfer pulley from old pump to new (if reusing pulley) by removing center nut and using a puller/installer. Compare pump mounting points and rotate shaft to ensure it’s free.
7. Install new pump: mount, torque bolts to spec (if unknown, snug then follow pattern). Reconnect hoses with new sealing washers/threads sealant as required. Refit belt with correct tension (manufacturer spec or about 7–12 mm deflection midspan depending on belt).
8. Fill reservoir with correct fluid to specified level. Leave caps loose for bleeding.
9. Initial bleed: start engine at idle and slowly turn steering wheel lock-to-lock several times to purge air. Monitor fluid level and top up. Do not run prolonged with low fluid.
10. Check for leaks, noise. After test, re-torque fittings and check hose clamp security.

B. Replace/overhaul steering control valve or steering gearbox
When to do: steering drifts, hard to center, internal leakage, severe play from the box.
Note: these gearbox assemblies are heavy and can be rebuilt or replaced as complete units.
Steps for replacement:
1. Park, chock, support front axle with stands.
2. Center steering wheel and lock front wheels straight (mark if necessary).
3. Relieve system pressure: run engine slowly and move wheel to center, shut off. Cap hoses.
4. Disconnect drag link and pitman arm: remove cotter pins and nuts, use puller to separate.
5. Disconnect hydraulic hoses to the box/valve — catch oil and cap lines.
6. Remove mounting bolts for steering box; support the box and lower out of tractor.
7. If rebuilding: disassemble in clean bench area, replace seals, spools, bushings per rebuild kit, use press where needed, replace bearings. Inspect worm shaft and sector shaft for wear; replace if beyond spec.
8. Install new/rebuilt box: align input shaft with steering column, ensure splines seat fully. Bolt to frame and torque per manual.
9. Reconnect hydraulic hoses with new crush washers/threads sealant.
10. Refit pitman arm and drag link—ensure correct orientation and torque. Refit cotter pins.
11. Refill and bleed: fill reservoir, start engine and slowly move wheel lock-to-lock to purge air. Check for correct centering and any unusual free-play.
12. Adjust lash if gearbox has adjustable sector (follow manual procedure): often involves locking down a nut/washer to set endplay.

C. Replace steering cylinder rod seals
When to do: visible rod leak, loss of force.
Steps:
1. Support tractor safely and relieve pressure. Center wheels.
2. Remove cylinder from linkage (disconnect pins) and hoses, cap hoses.
3. Mount cylinder in vice or bench with protective jaws. Slowly extend rod and drain fluid.
4. Disassemble gland/nut, carefully remove rod and piston. Inspect rod surface for scoring — if deeply scored, replace rod/cylinder.
5. Replace seals, back-up rings, wipers with kit. Clean bore thoroughly and lightly lubricate seals with hydraulic oil before assembly.
6. Reassemble with correct torque on gland/nut (do not over-torque). Reinstall cylinder, reconnect hoses with fresh seals, torque fittings.
7. Refill and bleed system.

D. Hose/fitting replacement
When to do: visible leakage, old cracked hoses, fittings damaged.
Steps:
1. Depressurize system.
2. Remove old hose, cap lines.
3. If possible have replacement hoses made to exact length with correct crimped ends. If you replace with braided hose ends, ensure pressure rating adequate.
4. Reconnect using new crush washers or thread sealant as required.
5. Tighten to snug; do not over-tighten and strip threads.
6. Fill and bleed system.

Bleeding/purging routine (very important)
- Why: air causes spongy steering, cavitation noise and damage.
- Standard procedure:
1. Fill reservoir to correct level with clean oil.
2. With engine off, slowly turn steering wheel from lock-to-lock several times to move fluid and dislodge big pockets of air.
3. Start engine at idle; with someone in cab (or carefully sitting), slowly move wheel lock-to-lock several times, pausing at each direction to allow bubbles to rise and reservoir to be topped up.
4. Monitor reservoir level and top up as necessary. Repeat until no bubbles appear and steering response is consistent.
5. After bleeding, run tractor and check for leaks and for wheel centering. Re-check fluid level when hot and cold.
- Tip: keep cap off only during bleeding; do not run pump dry. Place paper towel over cap opening to avoid dirt.

Adjustments and final checks
- Mechanical play: measure free-play at wheel (spec in manual). If excessive, adjust box lash or replace worn parts.
- Wheel alignment: when box or components replaced, check toe-in and wheel alignment and adjust tie rods as required.
- Pressure/spec checks: if available, test pressure with gauge to ensure pump/valve are within spec.
- Check belt tension after a few hours of run time.
- Replace hydraulic oil and filter if contaminated; if serious contamination, flush system.

Common pitfalls and how to avoid them
- Not capping lines/ports: leads to contamination and rapid damage to valves and pumps. Always cap immediately.
- Running pump dry: destroys pump quickly.
- Not bleeding properly: leaves air → noise and erratic steering.
- Reusing old hoses or improper fittings: causes leaks or burst lines.
- Ignoring mechanical wear: replacing pump won’t fix play due to worn pitman/rod ends or gearbox.
- Overfilling reservoir: leads to foaming; maintain correct level.

Typical maintenance tips to avoid future repairs
- Check hydraulic oil level weekly and fluid condition monthly.
- Replace hoses/clamps every few years or when cracking appears.
- Keep reservoir cap and strainer clean; change fluid/filter per manufacturer interval.
- Keep belt at correct tension.
- After any steering work, road-test and re-check everything after short interval.

Quick troubleshooting cheatsheet
- Heavy steering + good fluid, pump noisy = pump issue or belt slip.
- Heavy steering + low/no pressure reading = pump or relief valve fail.
- Steering drifts off center = valve or internal leak in gearbox/cylinder.
- Sudden loss of assist + leak under tractor = large hose or fitting failure.
- Play wheel but hydraulic pressure normal = mechanical linkage or gearbox wear.

Closing notes
- Specific torque values, pressure specs and oil grade vary by exact Fiat model and serial range — consult the factory service manual for your model for precise numbers. The procedures above match the hydraulic-assist steering layout used on these Fiat models and will guide you step-by-step as a beginner mechanic through diagnosis, pump/valve/box/cylinder repair or replacement, and bleeding and testing.
- Work methodically: clean parts, cap ports, keep a parts list and organize fasteners — hydraulic systems tolerate no dirt.

No unnecessary chatter — follow the procedures above, work safely, and refer to the factory manual for model-specific numbers and drawings.
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