About the Massey Ferguson MF135

Massey Ferguson developed a wide range of agricultural vehicles and have a large share in the market across the world especially in Europe. The next big selling model was the MF135, widely popular because of its reliability and power compared with other tractors at the time. This was the first model in the MF 100 series. The Massey Ferguson 135 is a popular tractor. In fact it is one of the most popular tractors for vintage and classic enthusiasts.

Massey Ferguson MF135 and MF148 Tractor factory workshop and repair manual

Tools & supplies
- Correct replacement belt (measure old belt or get OEM/aftermarket belt for MF135 M148; if it’s a serpentine conversion get the exact length and rib count)
- Socket set (8–19 mm common sizes), ratchet, extensions
- Combination wrenches
- Long pry bar or large screwdriver (for moving alternator / tension arm)
- Breaker bar or long-handled ratchet (for automatic tensioner square head if fitted)
- Torque wrench (for final bolt torque)
- Belt tension gauge or ruler/tape for deflection check (optional)
- Gloves, eye protection
- Wheel chocks, jack stands (if you need to raise the front)
- Wire brush & shop rag (clean pulley grooves)
- Replacement tensioner/idler pulley if worn (recommended)

Safety first
- Park on level ground, engage parking brake, chock wheels.
- Engine off, key removed, battery negative disconnected.
- Let engine cool. Keep hands/jewelry away from pulleys.
- Support the tractor safely if you must work underneath or remove guards.
- Use eye protection when prying and when checking pulleys.

Preliminary checks
1. Verify belt type and routing: note whether your MF135 M148 uses individual V-belts or a single serpentine/multi‑rib belt (many MF135s retain V‑belts; some owners fit single-belt conversions).
2. Take photos of belt routing from multiple angles or draw a routing diagram before removal.
3. Inspect pulleys, tensioner, and brackets for wear, play, or damaged grooves. Replace worn idler/tensioner/alternator bearings before fitting a new belt.

Step‑by‑step — manual tension (common on older MF135)
1. Disconnect battery negative.
2. Loosen the alternator pivot bolt (do not remove). Loosen the tensioning bolt/nut on the alternator adjusting bracket sufficiently so the alternator can swing.
3. Insert a pry bar between alternator and bracket and lever the alternator inward toward the engine to relieve belt tension. Some tractors use a separate tensioner bolt; turn that to slacken the belt instead.
4. Remove the old belt from around pulleys.
5. Clean pulley grooves with a wire brush to remove debris.
6. Route the new belt according to the photos/diagram: ensure ribs seat fully in grooves and belt lies flat on each pulley.
7. Pull the alternator outward slowly while checking belt seating and apply tension by tightening the tensioning bolt or moving the alternator until correct tension is reached.
8. Tighten the alternator pivot bolt to specified torque (if unknown, tighten securely but avoid over‑torquing; check service manual when available).
9. Reconnect battery negative.
10. Start engine briefly and observe belt operation (listen for squeal, watch tracking). Stop engine and re‑check tension and pulley alignment, re‑tighten bolts if necessary.

Step‑by‑step — automatic tensioner / serpentine style
1. Disconnect battery negative.
2. Locate the tensioner pulley and fit a breaker bar/long ratchet into the square drive or use the appropriate hex/bolt on the tensioner.
3. Rotate the tensioner to relieve pressure on the belt (direction depends on tensioner orientation), slip belt off one pulley, and slowly release the tensioner.
4. Remove the belt and clean pulleys.
5. Route new belt per routing diagram, leaving it off one easy-to-remove pulley (often the tensioner).
6. Rotate the tensioner again and slip the belt over the final pulley, then slowly release tensioner to apply tension.
7. Double-check that the belt seats correctly in all grooves and that rib orientation is correct.
8. Reconnect battery negative and run engine briefly to confirm proper operation.

How to set correct belt tension
- For V-belts: a typical rule is about 1/2" (12 mm) deflection at midpoint of longest span with moderate thumb pressure — check service manual if available.
- For serpentine with automatic tensioner: the tensioner sets tension automatically; ensure tensioner has full travel and is not bottomed out.
- Use a belt tension gauge for accurate readings if available.

How the main tools are used
- Pry bar/large screwdriver: used as leverage to move alternator/tension arm to relieve or increase tension. Apply force slowly and hold securely when fitting the belt.
- Breaker bar/ratchet on tensioner: rotates the tensioner spring assembly to release belt tension so you can remove/install.
- Torque wrench: used to tighten pivot and bracket bolts to correct torque to prevent slippage or bracket deformation.
- Wire brush/cloth: cleans pulley grooves so the new belt seats properly.

Replacement parts commonly required
- Correct length belt (or set of V-belts if not converted)
- Tensioner assembly (if automatic)
- Idler pulleys (if worn/noisy)
- Alternator mounting hardware (if damaged)
- If belts were transferred between drives: consider replacing fan belt, alternator belt, and PTO belt concurrently for long-term reliability

Common pitfalls & how to avoid them
- Wrong belt length or type: measure old belt or confirm OEM part first.
- Incorrect routing: always photograph/draw routing before removal.
- Insufficient/over tensioning: leads to slippage or premature bearing/belt failure — use deflection guideline or belt gauge.
- Damaged/dirty pulleys: grooves or rust cause rapid belt wear — clean and replace damaged pulleys.
- Loose mounting bolts: a slipping alternator will re‑slacken belt and damage bracket — torque properly.
- Forcing belt onto tensioner: when using an automatic tensioner, don’t let it snap back uncontrolled — hold it slow and steady.
- Not replacing worn tensioner/idler: new belt on worn pulleys will fail quickly.

Final checks
- Run engine and observe belt for correct tracking and noise.
- Re-check tension after 10–20 minutes of operation and again after a few hours; many belts settle and need minor readjustment.
- Inspect after first day of use for wear, fraying, or glazing.

End — follow local manual specs where available; replace worn pulleys/tensioner at the same time for best results.
rteeqp73

### Crankshaft Position Sensor Replacement on Massey Ferguson MF135 M148 Tractor

#### Tools Needed:
1. **Socket Set** (Metric and SAE)
2. **Wrench Set**
3. **Screwdriver Set**
4. **Torque Wrench**
5. **Pliers**
6. **Multimeter** (for electrical testing)
7. **Shop Rag** or **Paper Towels**
8. **Safety Glasses**
9. **Gloves**

#### Safety Precautions:
1. **Disconnect the Battery**: Always disconnect the negative battery terminal to prevent electrical shock or short circuits.
2. **Work on a Level Surface**: Ensure the tractor is on a stable, level surface to prevent it from rolling.
3. **Use Personal Protective Equipment (PPE)**: Wear gloves and safety glasses to protect against dirt and debris.
4. **Allow Engine to Cool**: Ensure the engine is cool before starting work to avoid burns.

#### Step-by-Step Procedure:

1. **Locate the Crankshaft Position Sensor**:
- The sensor is typically located near the crankshaft on the engine block. Refer to the service manual for the exact location.

2. **Remove Obstructions**:
- Depending on the tractor's configuration, you may need to remove components such as the air intake or covers to access the sensor.

3. **Disconnect the Electrical Connector**:
- Carefully unplug the electrical connector from the crankshaft position sensor. Use pliers if necessary to avoid damaging the connector.

4. **Remove the Sensor**:
- Using the appropriate socket/wrench, unscrew the bolts or screws holding the sensor in place.
- Gently pull the sensor out of its housing. Be cautious not to damage the surrounding components.

5. **Inspect the Sensor and Connector**:
- Check for any signs of wear, corrosion, or damage on the old sensor and the connector. Clean any debris in the area.

6. **Install the New Sensor**:
- Place the new crankshaft position sensor into the housing. Ensure it fits snugly.
- Tighten the bolts/screws to the manufacturer's specified torque settings using a torque wrench.

7. **Reconnect the Electrical Connector**:
- Plug the electrical connector back into the new sensor. Ensure it clicks into place securely.

8. **Reassemble Any Removed Components**:
- Reinstall any components that were removed to access the sensor, ensuring all bolts/screws are properly tightened.

9. **Reconnect the Battery**:
- Reconnect the negative terminal of the battery.

10. **Test the Sensor**:
- Start the engine to ensure it runs smoothly. Use a multimeter to check the signal output from the sensor if necessary.

#### Common Pitfalls to Avoid:
- **Forcing the Sensor**: Do not force the sensor into place; it should slide in easily. Forcing can cause damage.
- **Neglecting Torque Specs**: Always use a torque wrench to avoid over-tightening, which can damage the sensor or housing.
- **Ignoring Electrical Issues**: If the new sensor does not resolve the issue, check the wiring and connectors for damage or corrosion.
- **Not Cleaning the Area**: Ensure the area around the sensor is clean before installation to prevent debris from entering the engine.

#### Replacement Parts:
- Always use OEM or high-quality aftermarket parts that meet specifications for the MF135 M148. Ensure the part number matches the original sensor to avoid fitment issues.

This procedure will help you successfully replace the crankshaft position sensor on a Massey Ferguson MF135 M148 tractor with safety and efficiency.
rteeqp73

Summary: Replacing the drive belt(s) on an MF135/M148 is a straightforward mechanical job if you follow safety steps and check the pulleys and tensioning system while you’re at it. Below I explain what every component does, why the repair is needed, what can go wrong, and give a clear, step‑by‑step procedure written for a beginner mechanic.

Important safety first
- Work with the engine OFF, key out, and battery negative disconnected.
- Let the engine cool completely before touching the fan, water pump, or other hot parts.
- Chock wheels and set parking brake.
- Wear gloves and eye protection.
- Don’t put your fingers between a belt and a running pulley.

What you’re dealing with (components and what they do)
- Engine crankshaft pulley (harmonic balancer on some machines): main drive pulley that puts power into the belt.
- Fan (direct- or hub-mounted): pulls air through the radiator to cool the engine. Sometimes mounted on the water pump or crank pulley.
- Water pump pulley: driven by belt to circulate coolant.
- Generator or alternator and its pulley: charges battery / powers electrical system. Older MF135s often have a generator; some conversions use an alternator. Their mounting usually pivots.
- Idler pulley(s) and/or tensioner: maintain correct belt tension and routing. Older tractors may use a manual adjuster (pivot + long adjustment bolt) rather than an automatic tensioner.
- Belt (V-belt or multi-rib/serpentine): rubber element that transmits power from the crank to accessories. On classic MF135 tractors the original design uses V-belts; some later or modified tractors may have a multi‑rib belt or a single conversion belt.
- Mounting/adjustment bolts, pivot bolt, locknuts: hold and adjust the generator/alternator or idler.

How the system works — the theory (simple)
- The engine crank pulley is the “engine’s shoe” rubbing on a rubber band (the belt). The crank turns the belt, the belt wraps pulleys and makes the water pump, fan, and generator/alternator spin. If the belt is loose, it slips — just like a loose bicycle chain won’t push the wheel well. If the belt is too tight, it stresses bearings (wheel bearings → alternator/water pump bearings). Tension must be correct for power transfer and component life.

Analogy: imagine the belt as a bicycle chain and the pulleys as sprockets. If the chain is slack, it skips and makes noise; if too tight, the wheel bearings wear out faster.

Why replacement is needed
- Age and wear: rubber hardens, cracks, ribs separate, small chunks go missing.
- Contamination: oil or coolant softens/degrades the rubber.
- Stretching and loss of elasticity leads to slipping.
- Noise or visible damage, or if the belt breaks — engine will overheat (fan/water pump off) and electrical charging will stop (generator/alternator off).

Common failure symptoms
- Squealing on startup or under load (slip).
- Overheating (fan/water pump not effectively driven).
- Battery not charging (generator/alternator not driven).
- Visible cracks, glazing (shiny hard surface), frayed edges, or missing rib(s).
- Belt jumps off pulleys (misalignment or wrong routing).

What can go wrong if you replace incorrectly
- Wrong belt length or type → poor fit, noise, or rapid wear.
- Incorrect routing → loss of function, interference, quick failure.
- Insufficient or excessive tension → slipping or premature bearing failure.
- Damaged or seized pulley/bearing left in place → new belt fails quickly.
- Loose bolts → components shift and belt comes off; safety hazard.

Tools and parts you’ll need
- Replacement belt(s) — correct type and size for your setup. Check parts manual or measure old belt (wrap with tape and measure length), count ribs if serpentine.
- Basic hand tools: wrenches and sockets (common sizes for MF135: 9/16", 1/2", 3/4" or metric equivalents — have a set).
- Screwdrivers, pliers.
- Pry bar or long screwdriver (to lever alternator/generator for tension on manual systems).
- Torque wrench (recommended where torque values are specified).
- Straightedge or long level to check pulley alignment.
- Belt tension gauge (optional) or a ruler and a scale for deflection method.
- Cleaning rags, solvent for degreasing pulleys.
- Replacement idler/tensioner or bearings if pulleys are noisy or rough.

Preparation: identify your belt type on the tractor
- Inspect: older original MF135s use one or more V-belts. If you have a single modern multi-rib belt installed, treat it as a serpentine. The way you tension is similar: pivoting generator/alternator or adjustable idler provides tension. Replace with the same style used currently unless converting intentionally.

Step-by-step replacement (beginner-friendly)
1. Safety and prep
- Park on level ground, chock wheels, engage parking brake.
- Disconnect battery negative terminal.
- Let engine cool.

2. Expose the belt and routing
- Remove grill or fan shroud if needed for access (usually a handful of bolts).
- Sketch or take a photo of belt routing before removal — if you remove the belt, you need to put it back the same way.

3. Inspect pulleys and components
- Rotate each pulley by hand. They should spin smoothly with no roughness or play. If you feel grinding, replace that pulley or bearing.
- Check pulley grooves for glazing, nicks, or oil. Clean them with solvent and rag. Oil-contaminated pulleys must be cleaned and oil source fixed.
- Check that bolts and mounts are not loose or cracked.

4. Release belt tension
- On pivoting generator/alternator: loosen the pivot bolt (don’t remove it), then loosen the adjusting/lock nut and turn the adjustment bolt to move the generator/alternator inward to release tension.
- On systems with an idler/tensioner: loosen the tensioner lock bolt and rotate the tensioner to relieve tension.
- If a fan nut must be removed to access the belt, do so only when engine is cool and you have a proper wrench. Usually you don’t remove the fan unless necessary.

5. Remove old belt
- Slide the belt off pulleys, noting routing. If it’s a V-belt, it will seat into the pulley V groove. For multi-rib belts, ensure ribs align with groove pattern.

6. Compare belts
- Lay old and new belts together to verify length and rib count. New belt should match old one in profile and length.

7. Install new belt
- Route the new belt on all pulleys except the one used for applying tension (usually the alternator/generator or idler). Make sure the ribs sit correctly in the grooves and the belt seats fully.
- Use a bit of leverage (pry bar) on the pivoting unit if needed to fit the belt, but avoid forcing the belt over pulleys in a way that bends or twists it.

8. Apply proper tension
- Manual method (common for MF135): move the alternator/generator out using adjustment bolt until belt has the correct deflection.
- Deflection rule of thumb: at the longest span, with moderate thumb pressure (about 10 lbs / 45 N), belt should deflect about 1/4"–1/2" (6–12 mm) for multi-rib belts; for older V-belts ~1/2" (12 mm) per foot of span. If you have a belt tension gauge, follow the manufacturer’s spec. If unsure, aim for a bit firmer rather than too loose — but not rock hard.
- Tighten pivot and lock bolts while maintaining tension. Ensure you torque bolts to a firm snugness; consult manual for exact torque values — if you don’t have them, tighten solidly but don’t over-torque to avoid damaging threads.

9. Alignment check
- Use a long straightedge across pulley faces — they should be coplanar (in the same plane). Misalignment causes rapid wear or belt throw-off. Adjust mounting if needed.

10. Final checks
- Spin pulleys by hand again to check for binding.
- Reconnect battery negative.
- Start the engine and observe belt behavior at idle. Listen for squeal and watch for wobble or misrouting.
- Shut off engine and re-tighten pivot bolts if anything moved.
- Reinstall shrouds/grill.

Measurement note: if you’re uncertain about the “feel” method, many belt suppliers and repair manuals give specific deflection specs or a recommended tension test force. Using a simple spring scale can quantify your thumb pressure.

When to replace other parts at the same time
- If pulleys show wear, bearings are noisy, or the tensioner is weak, replace them while you have access. A new belt on worn pulleys will wear quickly.

Troubleshooting after fitting
- Squealing: too loose or glazed belt or contaminated pulleys. Readjust tension, clean pulleys, replace belt if glazed.
- Belt tracking off pulleys: misalignment or incorrect belt size. Fix alignment or use correct belt.
- Overheating persists: check that the fan actually spins when running and the water pump impeller isn’t failing.
- Charging issues persist: check alternator/generator and wiring after belt verified.

Quick inspection checklist after a few hours/days of operation
- Recheck belt tension — belts can seat and relax slightly. Retension if needed.
- Inspect for oil or coolant leaks onto belt. Fix leaks promptly.

Parts selection tips
- Use OEM or quality aftermarket belts designed for the tractor. Check parts books or belt diagrams for MF135 or measure the old belt.
- If converting from multiple V-belts to a single serpentine, plan carefully and confirm alignment and pulley profiles (not always a straightforward swap).

Final practical tips
- Keep the old belt until you’re sure the new one runs properly — it’s useful for length/profile reference.
- Don’t use “belt dressing” as a long-term solution — it masks problems.
- If you aren’t confident about detecting bearing noise or pulley wear, change the idler and tensioner when replacing a very old belt — cheap insurance.

That’s the full beginner mechanic’s walkthrough — components, theory, failure modes, and a stepwise replacement method. Follow safety, confirm belt type and length before buying, and inspect pulleys and bearings while you’re in there.
rteeqp73