Short, ordered explanation with theory and how the repair fixes the fault.

1) What the blow‑by system is / why it matters
- Theory: combustion gases that bypass piston rings enter the crankcase (blow‑by). Those gases carry vapour and oil mist. The blow‑by tube/PCV path vents them back to the intake (or to atmosphere on some machines) so crankcase pressure stays low and the engine doesn’t push oil out seals or contaminate oil.
- Normal: small controlled flow returned to intake. Excessive blow‑by (high crankcase pressure, oil in intake, blue smoke, oil leaks) indicates either a venting blockage or internal engine wear (rings/cylinders/valves).

2) Typical failure modes and how they produce symptoms
- Blocked/rotted blow‑by tube, clogged PCV/valve or a bad seal: prevents proper venting → positive crankcase pressure → oil leaks, oil sucked into intake, poor idle/smoke. Repairing the tube/PCV fixes venting and symptoms if the root cause is just blockage.
- Excessive internal blow‑by from worn rings, scored cylinders or blown head gasket: even with an intact tube you’ll still have high blow‑by. Replacing the tube/PCV only masks symptoms briefly; proper fix is ring/cylinder/head repair.

3) Diagnosis, in order (to determine whether tube repair will cure the fault)
1. Visual/smell clues: oil in intake manifold or air cleaner, oil on underside of rocker/valve cover, blue smoke on acceleration.
2. Inspect tube and PCV: follow the hose from valve cover to intake/airbox; check for softening, cracks, blockages, collapsed sections or clogged PCV valve/grommets.
3. Check crankcase pressure: remove oil filler cap (engine at idle, warmed) and feel for strong positive pressure or heavy blow. (If you prefer instruments, use a simple vacuum/pressure gauge on the valve cover port.)
4. Quick root‑check: if tube/PCV clogged and pressure abnormal, clear/replace tube and PCV then re‑test. If pressure remains high, do compression or leak‑down test to assess piston ring/cylinder condition.

4) Ordered repair steps for the blow‑by tube/vent path (what you do and why each step fixes the fault)
1. Safety: engine cold or cooled; disconnect battery if you’ll remove intake components. (Prevents burns/shorts.)
2. Locate vent hose/PCV: it runs from the valve/rocker cover to the intake or air cleaner on the Toyota B family. Inspect routing and attachment points visually.
3. Remove the hose/tube: loosen clamps and pull from fittings. Inspect inside for tarry deposits, oil sludge, kinks or collapse. (This reveals blockages or physical failure.)
4. Remove and inspect the PCV valve/grommet: shake the PCV — it should move freely; replace if stuck. Replace perished rubber grommets. (A stuck PCV blocks flow or passes uncontrolled flow.)
5. Clean mating surfaces and intake area: remove oil residue from intake manifold and throttle region so new seal/clamp seats correctly. (Prevents leaks and oil ingestion later.)
6. Fit new tube/PCV/grommets: replace with OEM or equivalent hose and a new PCV valve. Route and secure with clamps. (Restores proper, unobstructed vent path and correct sealing.)
7. Start engine and re‑check: verify no heavy blow at filler, check idle and absence of oil in intake. Confirm reduced smoke and no new leaks. (Confirms the vent path is functioning.)
8. If symptoms persist, perform compression or leak‑down and plan ring/cylinder repair. (If internal wear remains, tube replacement is only temporary.)

5) How the repair fixes the fault (concise)
- Replacing/cleaning the blow‑by tube and PCV removes blockages and restores the designed low‑pressure vent path. That eliminates positive crankcase pressure, which stops oil being forced out of seals or drawn into the intake and reduces oil‑fouled intake and smoke.
- Important: if excessive blow‑by is caused by worn rings or cylinder damage, the tube repair reduces secondary symptoms but does not reduce the internal blow‑by source. Only reconditioning (rings/cylinders or full rebuild) reduces the blow‑by volume at the source.

6) Quick checklist of tools/parts
- Replacement blow‑by hose/tube, PCV valve, grommets/seals, hose clamps
- Basic hand tools, shop rags, throttle/intake cleaner, optionally a pressure/vacuum gauge and compression/leak‑down test kit

Done.
rteeqp73

Big Toyota B series diesel

How to Toyota b2 diesel engine start, Toyota b3 engine How to Toyota b2 diesel engine start, Toyota b3 engine.

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Ordered, theory-focused guide to manual-transmission repair (applies to Toyota B / 2B–era manual gearboxes and similar designs). Emphasis is on why each action fixes the fault, not just how to turn bolts.

1) Components and operating principles (why things fail)
- Main parts: input shaft (driven by clutch), counter/countershaft (layshaft), output shaft, gears (fixed to shafts or free on splines), dog teeth or synchronizers (synchro rings + sleeves) for engaging gears, shift forks/rails, bearings (radial/thrust), seals/gaskets, shift linkage.
- How it works: engine torque -> clutch -> input shaft -> layshaft -> selected gear pairs -> output shaft. Synchros match shaft speeds by using friction cones so dog engagement occurs smoothly. Bearings constrain shafts and set mesh/axial positions. Oil lubricates friction surfaces and bearings.
- Common failure modes and why: worn synchro friction (gear clash/hard shift) because cones lose material/steel contact; worn dog teeth or chamfers (jumping or not engaging) due to impact/clutch slip; bearing wear (growl/whine, play) from load/contamination causing misalignment and gear noise; seals leaking => oil loss => accelerated wear; bent shift forks/linkage wear => incomplete engagement; worn gear teeth (pitting/chipping) from overload or misalignment.

2) Diagnosis — theory-driven symptom mapping (what damaged component causes which symptom)
- Grinding on shift or double-rev required to engage upshift → worn synchro cones or hub/sleeve wear. Theory: synchro no longer creates friction to match speeds so dogs strike gear teeth.
- Pop-out of gear or jump → worn dog teeth, weak spring retention, or bent shift fork (engagement cannot hold). Theory: engagement geometry no longer locks gear to shaft.
- Whine/roar proportional to vehicle speed → worn/damaged bearings or bad gear tooth mesh. Theory: bearing clearance or gear tooth profile has changed, creating vibration/noise.
- Oil leak/low level → external seal failure; low oil leads to overheating and accelerated wear.
- Hard/slow shifts on certain gears only → worn specific synchro or misaligned selector mechanism.

3) Preparation & safety (theory: isolation and correct environment)
- Rationale: cleanliness and known torque/clearance values are critical. Contamination or incorrect torque leads to repeat failure. Have service manual for torque/specs; use proper tools (press, dial gauge, micrometer, torque wrench).
- Drain fluid before opening to avoid mess and to inspect oil for metal flakes (indicates internal damage).

4) Removal and separation (theory: preserve alignment & document)
- Remove transmission from vehicle, separating clutch/engine components and linkage. Mark relative positions, photograph assemblies and tag parts. Theory: transmissions are assemblies of fitted parts; correct orientation during reassembly prevents mis-shimmed bearings and mis-timed selectors.

5) Controlled disassembly (theory: preserve measurement references)
- Disassemble progressively: remove tail housing, shift forks/rails, synchro hubs/sleeves, gears, bearings, shafts. Keep components in order.
- Theory: many components wear together into a matching relationship (bearings, shims, gear mesh). Preserving order and noting end-play prevents introducing axial/mesh errors at reassembly.

6) Inspection and measurement (theory: compare to limits, measure wear)
- Bearings: check radial play and noise; measure inner/outer races for pitting. Theory: bearings control shaft position; wear changes centerlines and mesh.
- Gears: inspect teeth for pitting, chips, wear pattern; measure backlash and runout. Theory: gear profile must match to transmit torque without stress concentration.
- Synchros: examine friction cones for glazing, missing material, or excessive scoring; check hub splines and sleeve dogs. Theory: friction surface must provide enough torque transfer to synchronize speeds; hub/sleeve wear reduces engagement reliability.
- Shafts: check splines and journal wear, straightness. Theory: bent shafts change mesh and create noise/rapid wear.
- Seals and bushings: check deformation. Theory: leaks and loose bushings allow contamination and movement.

7) Decide repair vs replace; machining needs (theory: tolerances and material limits)
- Replace synchro rings/hubs/sleeves if cones worn beyond spec — machining cannot restore friction material reliably. Theory: synchros rely on precise cone angles and surface finish; replacement restores friction coefficient and geometry.
- Replace bearings and seals — minimal risk and restores shaft support and sealing. Theory: new bearings re-establish correct radial/axial clearance and eliminate vibration/noise.
- Regrind/replace shafts or remachine bearing journals only if within allowable limits; use replacement gears if tooth profile damaged. Theory: machining changes dimensions — if beyond shimming range, replace to maintain gear mesh and endplay.
- Replace shift forks if bent or worn at contact points; worn fork-to-sleeve clearance leads to poor engagement. Theory: forks locate the sleeve; wear changes engagement geometry.

8) Repair actions and why they fix the fault (ordered)
- Replace worn synchro rings and sleeves: restores friction cone contact and corrects the speed-matching function so dogs engage without clash.
- Replace worn hub/sleeve dogs or gear dog teeth: restores positive mechanical lock and prevents pop-out/jump.
- Replace bearings and renew bearing races as needed: re-establishes correct shaft radial/axial positions, reducing noise and preventing mis-mesh that causes gear and bearing failure.
- Correct shims/endplay: measure shaft endplay with dial gauge; fit correct shims. Theory: axial clearance controls gear mesh and bearing preload; improper endplay causes noise/rapid wear or binding.
- Correct backlash and gear mesh pattern: use plastigage or paint pattern to set axial position or shims so contact pattern centers on tooth face. Theory: correct mesh distributes load properly and avoids concentrated wear/pitting.
- Replace seals and gaskets: prevents oil loss and contamination, maintaining lubrication and longevity.
- Repair/replace shift forks/rails and adjust selector geometry: restores proper sleeve travel and alignment so gears fully engage. Theory: precise motion is needed to seat sleeves; worn rails allow misalignment leading to missed engagement.
- Clean and inspect all parts; deburr edges but do not remove functional material. Theory: contamination and sharp burrs cause premature wear.

9) Reassembly with proper tolerances (theory: restoring original geometry)
- Reassemble in original order, using specified torque for fasteners and correct bearing preload/shim thickness. Theory: torques and shims set preload and clamp loads that keep bearings and gears in designed positions; incorrect values alter dynamics and lead to failure.
- Use new gaskets/seals and correct grade of lubricants. Theory: correct oil viscosity forms adequate film thickness at operating temperatures and shear rates.

10) Testing and verification (theory: validate restoration)
- Bench-check free play, shift engagement through full range; measure endplay and backlash again. Theory: ensures restored geometry before reinstallation.
- Road test under controlled conditions: verify shift quality, noise, leaks. Theory: dynamic loads and temperatures reveal residual issues (thermal growth and load-induced deflections).

11) Common fault-specific fixes and the underlying fix mechanism (concise)
- Hard 2nd/3rd shift (classic symptom): replace synchro rings for those gears and inspect hub/sleeve dogs. Why fixes: synchro friction restored so shafts equalize speeds allowing smooth dog engagement.
- Noise/whine at certain speeds: replace worn bearings and correct gear mesh/shim. Why fixes: bearings set shaft centerlines and gear mesh; new bearings remove play and correct alignment reducing vibration.
- Gear pop-out: replace dog teeth, check fork geometry and linkage. Why fixes: restores positive lock and correct sleeve travel so gear cannot back out under torque.
- Leaking output seal: replace seal and check tail housing bore; why fixes: prevents oil loss which will otherwise starve bearings and synchros, halting progressive damage.

12) Prevention (theory: why problems recur and how to prevent)
- Keep proper oil type and level: correct film thickness prevents metal-metal wear.
- Maintain clutch function: slipping clutch causes heat and shock loads that damage synchros and dogs.
- Avoid abusive shifting (shift under heavy load when synchro is weak) to extend life.

Final note: follow a model-specific service manual for exact tolerances, torque specs, shim sizes and parts numbers. The theoretical steps above explain how each repair restores the mechanical relationships (friction, alignment, preload, sealing) that a manual gearbox needs to operate quietly and reliably.
rteeqp73