Short version up front: the EGR (exhaust gas recirculation) valve recirculates a small amount of exhaust into the intake to lower combustion temperature and reduce NOx. On older tractors like the MF135 (M148 engine family variants are similar), the EGR is usually a simple valve mounted between an exhaust crossover and the intake manifold and is vacuum‑ or mechanically actuated. Common problems are carbon clogging, failed diaphragm/actuator, or leaking gaskets. Below is a beginner‑friendly, step‑by‑step guide, with detailed descriptions of every component, what can go wrong, how to test, how to clean or replace, and why the repair is needed.

Safety first
- Work on a cold engine. Hot exhaust/intake metal will burn you.
- Park on level ground, set parking brake, chock wheels.
- Wear safety glasses and gloves; have good ventilation if using solvents.
- If the EGR valve is electrically controlled on your specific model, disconnect the battery before working on wiring.
- Keep rags and a small container for old gasket bits/solvent.

What the EGR system does (theory, in plain English)
- Purpose: Mix a controlled amount of exhaust gas back into the fresh air/fuel charge to reduce peak combustion temperature. Lower peak temperature → less formation of NOx (oxides of nitrogen). Think of it like adding a little stale, cooler air into a hot oven to keep the temperature from spiking.
- If the EGR is stuck open: too much exhaust enters the intake — engine idles poorly, stalls, and loses low‑end power (like breathing through a blocked, leaky straw).
- If the EGR is stuck closed or plugged: you get higher combustion temperatures and increased NOx; sometimes detonation/pinging or higher exhaust temps. Carbon builds up elsewhere over time.

Main components (detailed descriptions)
1. EGR valve body
- Metal casting bolted between an exhaust crossover/port and the intake manifold.
- Contains the valve seat and moving pintle/plate that opens to let exhaust gas flow into intake.
- Has bolt holes and a gasket surface.

2. Valve internals (pintle/seat or plate)
- The moving part that seals against the seat when closed. Carbon builds up on these surfaces and prevents proper sealing.

3. Actuator
- Two common types on older tractors:
a) Vacuum diaphragm actuator: rubber diaphragm with a rod connected to the valve pintle. A vacuum line pulls the diaphragm, opening the valve. A spring returns it closed.
b) Mechanical linkage/thermal actuator: less common; linkage moved by throttle or governor.
c) Some later models may have an electrically controlled actuator (solenoid or stepper) with a position sensor.
- Diaphragm failures: tears or hardened rubber leak vacuum so valve doesn't move.

4. Vacuum lines and vacuum source (if vacuum‑actuated)
- Rubber hoses that carry vacuum from the engine (manifold or vacuum pump) to the EGR actuator through a control solenoid/valve.
- Hoses age, crack, or split and leak vacuum.

5. EGR control solenoid/valve (if present)
- An electrical/solenoid valve that switches vacuum on/off to the EGR actuator according to conditions (governor/engine load). On older MF tractors there may be a simple vacuum tap or manual control instead.
- Can fail electrically or mechanically (stuck open/closed).

6. EGR passages / crossover
- Cast or bolted passages that route exhaust gas from the exhaust manifold/crossover into the intake manifold.
- Carbon and soot deposits build up here and can clog passageways.

7. Gaskets and seals
- Paper/metal gasket between EGR valve and manifold. If leaking, exhaust bypasses or leaks into bay.

8. EGR cooler (rare on MF135)
- Some modern systems cool the exhaust before recirculation; not typical on old MF tractors.

Symptoms that indicate EGR work is needed
- Rough idle, stalling at idle, poor low‑speed response — especially when warm.
- Black smoke (if too much EGR or running rich).
- Loss of power, hesitation on load.
- Engine pinging at high load (if EGR failed closed; less likely on simple tractors).
- Visible soot/carbon around the valve or intake manifold.
- Vacuum leaks in hoses (if vacuum‑actuated).

Tools and supplies you’ll need
- Basic metric socket set, spanners, screwdrivers.
- Pliers for hose clamps.
- Handheld vacuum pump with gauge (recommended) — to test vacuum actuators.
- Wire brush, brass brush, picks for carbon scraping.
- Carburetor/inlet cleaner or dedicated EGR port cleaner (avoid strong acids).
- Clean rags and a small container/tray for parts.
- New EGR gasket (always replace).
- Replacement vacuum hose if old/soft.
- Replacement EGR valve or actuator if cleaning won’t fix it.
- Torque wrench (optional) — tighten bolts evenly, don’t over‑torque.

Step-by-step: locate the EGR
- Typical location: between the exhaust crossover (a short pipe or port that connects exhaust to intake) and the intake manifold, usually on the side or top of the engine near the intake. On the MF135 it’s a compact component bolted to the intake/exhaust crossover; trace exhaust piping near the intake manifold.
- Identify vacuum hose to the actuator (if present) and the two or three bolts holding the valve in.

Removal (beginner level)
1. Work on a cold engine. Disconnect battery if electrical connections exist.
2. Photograph or note locations of hoses and any vacuum lines before disconnecting.
3. Remove the vacuum hose from the actuator first; plug it with a rag to prevent debris entering.
4. Unbolt the EGR valve from the manifold/crossover — usually 2–4 bolts. Keep bolts and old gasket.
5. Remove EGR valve and inspect ports and gasket surfaces.

Inspection (what to look for)
- Carbon build‑up on valve face, pintle, and in the passages.
- Torn or hardened diaphragm (if you can see it).
- Cracked or collapsed vacuum hoses.
- Soot/black deposit blocking holes in the EGR or intake manifold.
- Gasket surface damage.

Cleaning (when to clean vs replace)
- Clean if the actuator moves freely and diaphragm is intact; replace if diaphragm is torn, actuator is dead, or valve is heavily corroded.
- Use a brass brush and carb cleaner to remove carbon from the valve face and passages. A wire brush can be used carefully — don’t gouge sealing surfaces.
- Use picks/mirrors to clean small ports in crossover and intake; compressed air (briefly) to blow loose carbon out (wear eye protection).
- If you remove the intake manifold for deep cleaning, clean the mating surfaces and ports thoroughly.

Testing the actuator and valve
- For vacuum diaphragm:
- Connect a handheld vacuum pump to the actuator. Apply vacuum: the valve pintle should move smoothly and hold vacuum (no leak) when pulled. If vacuum leaks away quickly, the diaphragm is bad.
- With vacuum applied, visually check the pintle/plate opens and closes smoothly.
- For electrical solenoid/actuator:
- Check connectors for corrosion. Use a multimeter to check for expected resistance in solenoid coil (if service data available) or apply 12V momentarily to see movement (careful).
- Check vacuum lines: squeeze and inspect; replace any brittle or collapsed hoses.

Reassembly
1. Fit a new gasket between the valve and manifold.
2. Ensure mating surfaces are clean and flat.
3. Reinstall EGR valve and tighten bolts evenly until snug. Don’t overtighten — you can strip threads or crack castings. Hand tight + quarter turn is often enough on small bolts; use torque spec if you have a manual. (If uncertain, tighten gently until you feel resistance, then give a small additional turn.)
4. Reconnect vacuum hose and any electrical connectors.
5. Reconnect battery if disconnected.

Testing after reassembly
- Start engine and let it reach operating temperature.
- Check for vacuum leaks (hissing, smell, or soot blowing).
- Use the handheld vacuum pump again with the engine idling (if you can operate the EGR control) to actuate the valve and watch for changes in idle.
- On vacuum controlled systems: with engine at idle, opening EGR should typically cause roughness or a drop in RPM; that indicates it’s doing something. If no change, it may still be plugged or control not operating.
- Road/field test under load: look for restored power and smooth idle.

Common failures and how to fix them
- Carbon‑clogged valve or ports: clean as above. If ports are badly clogged and can’t be cleared, replace manifold/crossover or remove manifold for deep cleaning.
- Torn diaphragm: replace the EGR valve assembly (diaphragms are usually not serviceable on many older valves).
- Stuck pintle (carbon welded): sometimes tapping the valve while applying cleaning solvent frees it; if not, replacement is safer.
- Vacuum line leak: replace hose; test vacuum source.
- Faulty vacuum solenoid: replace or bypass temporarily for bench testing.
- Gasket leak: always use new gasket; if mating surface damaged, machine or replace part.
- Cracked valve body: replace entire valve.

Analogy to help remember how it works
- Think of the engine like a campfire stove. Fresh air is the oxygen you add to the fire. If it gets too hot and burns hotter than you want (making unwanted “smoke” like NOx), you add a little cooled, used air (exhaust) back into the cooking pot so the fire’s hottest spot doesn’t spike. The EGR valve is the little tap that admits that used air only when needed. If that tap is stuck open, you’re choking the fire; if stuck closed, parts overheat.

Parts to have on hand for a typical EGR job
- New EGR gasket, replacement vacuum hose, replacement EGR valve (if needed), small tube of anti‑seize (light) for bolts (optional), solvent and brushes.

Troubleshooting quick list
- No vacuum at actuator: check vacuum source and hoses.
- Vacuum present at actuator but valve doesn’t move: actuator linkage seized or broken.
- Valve moves but engine behavior unchanged: passages clogged or EGR not wired/controlled.
- Engine stalls/rough while EGR is supposed to be closed: valve leaking or gasket leak.
- Black smoke: excessive soot (could be too much EGR or poor combustion).

Final tips
- Don’t force the valve open with excessive leverage — you can bend the pintle or damage the seat.
- Replace small rubber hoses while you’re at it; cheap insurance.
- Keep track of knives/picks near gasket surfaces so nothing drops inside intake.
- If your tractor’s EGR is electronically controlled, basic electrical tests (voltage at connector when command is given) are needed in addition to vacuum tests.
- If you’re unsure about removing the intake or doing major disassembly, take photos at every step — they make reassembly easier.

Time estimate
- Simple remove/clean/reinstall: 1–2 hours.
- Deep clean of passages or replacement: 2–4 hours depending on access and parts.

This covers the purpose, parts, symptoms, testing, cleaning, removal, replacement, and common failures for an EGR valve on an MF135‑style tractor. Follow the steps and safety precautions; replace any part that shows mechanical or diaphragm failure.
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Tools & consumables
- Basic hand tools: metric/imperial sockets, ratchets, breaker bar, extensions, combination wrenches, screwdrivers, punch set.
- Torque wrench (0–200 ft·lb range).
- Engine hoist and stand (or secure cradle) — do not attempt major crank work with engine in place unless fully supported and accessible.
- Hydraulic press or flywheel puller / harmonic balancer puller.
- Micrometer (0–3" / 0–75 mm) for journal measurement.
- Dial indicator with magnetic base for endplay/runout checks.
- Plastigauge (correct width for typical main clearances).
- Feeler gauges.
- Soft-faced mallet, brass drift.
- Cleaning brushes, solvent, lint-free rags, gasket scraper.
- New bearings (main and connecting rod), thrust washers, front and rear crank seals, any required gaskets and O‑rings, new main cap bolts if specified as torque-to-yield or one‑time stretch bolts.
- Engine assembly lube (high pressure).
- Threadlocker (where specified), anti-seize for certain bolts.
- Shop manual for Massey Ferguson MF135 (M148 engine) — required for specs, sequences, tolerances.

Safety precautions
- Work on a flat, level surface with good lighting and ventilation.
- Disconnect battery before beginning.
- Use proper lifting equipment (engine hoist) and rated chain/straps. Never work under a suspended engine.
- Wear eye protection, gloves, and hearing protection as needed.
- Keep bystanders clear of the work area.
- Clean oil spills immediately; avoid slipping hazards.
- If unsure about any step, stop and refer to the factory manual or a qualified machinist.

Overview (what you are doing)
This procedure covers removing, inspecting and reinstalling/replacing the crankshaft on the MF135 (M148 engine family). It assumes the engine is removed from the tractor and on a stand or is otherwise fully accessible. If you only intend to remove the crank (e.g., for grinding or replacement), you’ll need to remove pistons/rods or at least rod caps to free crank rotation.

Step‑by‑step procedure

1) Preparation
- Get the factory workshop manual for exact torque values, bearing part numbers and crankshaft clearances.
- Label/photograph everything before disassembly (timing, wiring, linkages, orientation of caps).
- Drain engine oil and coolant (if applicable). Remove oil pan and oil pickup carefully.

2) Remove ancillaries and timing components
- Remove fan, pulley/harmonic balancer (use appropriate puller), timing cover, timing gears/chain/belt, camshaft gear if needed to access front of crank. Remove oil pump if it obstructs.
- Remove flywheel or flexplate (use correct bolts; note orientation and mark location). If clutch is present, remove clutch pressure plate and disc.

3) Mark components and cylinder heads
- If removing pistons, mark each piston and connecting rod and their caps so they return to same location and orientation. Keep rod caps with their rods in order and oriented correctly.

4) Remove connecting rod caps and pistons (if necessary)
- Rotate engine so each rod journal is at bottom to access rods. Remove rod cap bolts, remove caps, push pistons up into bore and secure with rope/safety strap or remove pistons from top if doing full disassembly. Keep rod bearings in order.

5) Remove main bearing caps
- Loosen main cap bolts in a crisscross sequence progressively to avoid distortion. Remove caps one at a time, mark orientation and order. Note any thrust washers/locating tabs and keep in order.

6) Remove crankshaft
- With all bearings/caps removed, carefully lift the crankshaft out of the block. Crankshafts are heavy; use two people or hoist. Avoid dropping or nicking journals.
- If stuck, gently pry using suitable drift points; do NOT lever on journals.

7) Inspect crankshaft and bearings
- Clean journals and bearing surfaces with solvent and lint-free rags.
- Measure each journal with micrometer at multiple positions (0°, 90°, 180°, 270°) to check diameter, taper and out-of-round. Compare to factory specs.
- Measure main and rod bearing saddles in block and compare.
- Inspect thrust faces for wear and measure axial play (when reassembled) with dial indicator.
- If journals are scored beyond allowable limits, crankshaft will need grinding (rebore) or replacement. If journals are within limits but marginal, consider undersize bearings during reassembly — consult manual and supplier.

8) Replace required parts
- Replace all main and rod bearings and thrust washers as a set. Do not reuse bearing shells.
- Replace front and rear crank seals when reinstalling.
- Replace any damaged bolts (rod/main) or stretch bolts as specified in manual.
- Replace oil pump gasket, oil pan gasket and any timing cover seals that were disturbed.

9) Clean and prepare block, caps and crank
- Deburr the oil holes, clean oil galleries with solvent and compressed air (block oil plugs in ears with rag to prevent debris entering).
- Inspect main cap bore faces for mating surfaces and clean.
- Apply assembly lube to bearing surfaces and journals during reassembly.

10) Install crankshaft
- Lower crank into place carefully onto new main bearing shells (ensure correct orientation of bearing tangs).
- Fit new thrust washers in correct location and orientation.
- Apply assembly lube on bearing surfaces.

11) Fit main caps and torque progressively
- Install main caps in original positions with new or reused bolts per manual. Tighten bolts in a progressive sequence (center outward) in several steps to final torque. Use factory torque specs. If bolts are stretch type, follow specified angle tightening method and replace bolts if required.
- After initial torque, check crank end play with dial indicator: mount base to block and push crank forward/back with suitable tool or pry; measure total movement and compare to spec. If out of spec, adjust thrust washers or contact machinist.

12) Check bearing clearances (Plastigauge method)
- Alternate method: with caps torqued to spec, remove them one at a time and use plastigauge on journals to confirm oil clearance. Procedure: place strip along journal, refit cap and torque to spec, remove cap and measure width of flattened plastigauge against scale. Replace bearings if clearances out of range. Do not rotate crank with plastigauge installed.
- Proper clearances and specification must be met. If boring/line‑boring or undersize bearings are required, take block to machine shop.

13) Refit rod caps/pistons
- If pistons were removed or pushed up, reinstall rods onto journals with new rod bearings, torque rod bolts to spec. Clean and lube surfaces and ensure correct bearing orientation.

14) Final checks and reassembly of ancillaries
- Rotate crank by hand through several revolutions; it should turn smoothly with even oil pressure when primed.
- Reinstall oil pump, timing gears/belt/chain aligning timing marks, timing cover, harmonic balancer/pulley, flywheel/clutch, oil pan with new gasket, seals and all ancillaries.
- Refill oil and coolant, prime oil system (crank for oil pressure without starting, or use pre-lube method), check for leaks.

15) Start-up and break-in
- Start engine and idle, monitor oil pressure and listen for unusual noises. Change oil/filter after initial run-in per manual.
- Check endplay and torque values again after a short running period if recommended.

Common pitfalls & how to avoid them
- Not marking parts: Always tag main caps, rod caps and pistons. Mixing orientation will destroy journals/bearings.
- Reusing bearings/seals: Replace main and rod bearings and crank seals every time the crank is removed.
- Incorrect torque/bolts: Use factory torque specs and replace stretch bolts. Overtightening or wrong sequence = bearing failure.
- Not checking clearances: Always measure journals and use plastigauge or micrometers. Guessing leads to seizure or low oil pressure.
- Dirt/contamination: Cleanliness is critical — contamination causes rapid engine failure.
- Damaging journals during handling: Protect journals; drops or nicks require machining.
- Incorrect thrust washer fitment: Wrong placement causes excessive endplay or binding.
- Attempting major crank work in situ: Access and safety are compromised; remove engine if possible.
- Forgetting to prime oil system before initial start: Leads to dry start and bearing damage.

When is replacement required
- Deep scoring, heat discoloration, cracks, or journal taper/out-of-round beyond service limits — crankshaft must be reground (to standard undersize) or replaced.
- If undersize grinding needed, you must fit corresponding undersize bearings and verify clearances.
- Replace front/rear seals, bearings, thrust washers and any one‑time use fasteners whenever the crank is removed.

Final note
Follow the MF135 (M148) factory workshop manual for exact torque figures, bearing part numbers and clearance limits — those are critical and vary by engine serial and production run. The steps above cover the full mechanical process; accuracy and cleanliness are the keys to a reliable reassembled engine.
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