What you’re doing: removing and reinstalling (or replacing) the oil pan on a Toyota 4Runner. This guide is written for a beginner mechanic and covers components, theory (how it works and why it fails), a safe step‑by‑step procedure, tools/consumables, common failure modes and troubleshooting. Vehicle specifics (year, engine) change hardware and exact torque specs, so treat exact numbers as examples and confirm final torque/specs from the factory service manual for your 4Runner.

Quick overview (analogy)
- The oil pan is the car’s oil “bucket” mounted under the engine. The oil pump uses a “straw” (pickup tube) that reaches into that bucket to draw oil and send it through the engine. The pan also has baffles (windage tray) that keep oil from sloshing away from the pickup, and a drain plug to empty the oil. The gasket or sealant between pan and engine block is like the rubber rim on a jar lid — it must seal but not be crushed or ripped.

Key components and what each does
- Oil pan (sump): stamped steel or cast aluminum container that holds engine oil when the engine is off.
- Drain plug (and crush washer): threaded plug to drain oil; washer provides a seal.
- Oil pickup tube & screen: rigid tube with a screened inlet that sits in the pan; it’s what the oil pump draws from.
- Windage tray / baffle(s): sheet metal that controls oil splash and keeps oil near the pickup during motion/acceleration.
- Gasket (molded rubber, cork, or paper) or RTV sealant: seals mating surfaces between pan and block.
- Pan bolts & washers / studs / dowel pins: fasteners and locators that hold pan to block and keep alignment.
- Oil level sensor (if equipped): threaded sensor sometimes mounted in the pan.
- Transmission crossmember / exhaust / skid plate: ancillary parts that often must be removed for access.
- Engine block mating surface: the flat surface on the block that the pan seals to.
- Oil filter: normally removed as part of the oil change when pan is off or engine is being serviced.
- Oil pump (internal to engine): draws oil from pickup; indirectly involved when you inspect/replace the pan.

Why this repair may be needed / how the system works
- Function: When the engine runs, the oil pump pulls oil from the pan through the pickup and pressurizes it through galleries to lubricate bearings, camshafts, etc. The pan simply stores oil and acts as the lowest point of the system.
- Why you remove the pan: to replace a leaking pan/gasket, repair a damaged pan (dent/crack), replace the pickup or pump, clear sludge or debris, or address a damaged torque converter/front of transmission leak that involves pan removal.
- Failure modes:
- Leaks from old/deteriorated gasket or failed RTV (oil pooling or dripping).
- Stripped drain plug threads (oil drips and can’t seal).
- Cracked or punctured pan from road debris or hitting a rock.
- Warped mating surface or uneven sealing causing leaks.
- Loose or missing bolts allowing leaks or pan movement.
- Clogged pickup or broken pickup tube causing oil starvation.
- Over-tightened bolts that strip threads in the block.
- Corrosion or rusted pan where bolts break when removed.
- Consequences if ignored: oil loss leading to low oil pressure and severe engine damage; contamination from debris; running with leaking oil is dangerous and environmentally illegal.

Tools & consumables (minimum)
- Floor jack and quality jack stands (do not rely on jack only). Wheel chocks.
- Oil drain pan, rags, shop towels.
- Socket set (metric) incl. extensions, universal joints.
- Torque wrench (appropriate range).
- Breaker bar, ratchet.
- Gasket scraper (plastic or brass preferred) and razor or gasket remover.
- Wire brush or Scotch-Brite pads, brake cleaner / parts cleaner.
- New oil pan gasket or OEM pan, new drain plug crush washer or new plug if needed.
- RTV silicone gasket maker (if factory uses RTV) — use Toyota-specified type if documented.
- New oil filter and correct engine oil/quantity.
- Replacement bolts if any are damaged, thread chaser/Heli-Coil kit if threads are stripped.
- Gloves, eye protection.
- Optional: magnetic pickup tool, drip tray, small pry bar, rubber mallet.

Safety and environmental notes (must-do)
- Work on level ground. Chock wheels and set parking brake.
- Use jack stands — never work under a car supported only by the jack.
- Let engine cool completely; hot oil and hot exhaust will burn you.
- Disconnect negative battery terminal if you will be working near sensors or wiring.
- Catch and dispose of used oil and contaminated rags at an authorized recycling facility.

General procedure (step-by-step, beginner-friendly)
This is a typical sequence for a 4Runner. Your model may vary — follow the service manual for exact steps, bolt counts, and torque specs.

1) Prepare
- Park on level surface, chock rear wheels, loosen front wheel lug nuts if you’ll remove wheels to ease access.
- Raise front of car with floor jack and support on jack stands under recommended lift points. Ensure stable.
- Place oil drain pan under drain plug.

2) Drain oil and remove oil filter
- Remove drain plug and let oil drain; remove oil filter. This reduces mess when pan drops.
- Reinstall drain plug finger-tight for now (or clean threads and leave removed — depends on pan removal order).

3) Remove obstructing components
- Remove skid plate, splash shields, heat shields, or crossmembers that block pan access.
- On some models you may need to remove or lower transmission crossmember or exhaust pipes. Support any dropped components safely.
- Label fasteners or take photos if needed to remember locations.

4) Unbolt items attached to pan
- Remove bolts around the pan perimeter. Count bolts and note any that are a different length — some holes use different length bolts or studs.
- Remove bolts for crossmember/heat shield if they attach to the pan.

5) Separate pan from block
- The pan may be sealed with RTV and will stick. Gently tap along the seam with a rubber mallet to break the seal. Do not force a screwdriver between surfaces indiscriminately — you can gouge the mating surface.
- Support the pan with a jack or have a second person. Lower slowly — the pickup may still be attached or wires/sensors may be connected.

6) Inspect internals
- Remove windage tray/baffles if present. Inspect pickup screen for sludge/metal debris. If you see lots of metal, do not just reassemble — investigate bearings/cam journals and oil pump.
- Clean pan: drain residual oil, scrape off gasket material.

7) Clean mating surfaces
- Remove old gasket or cured RTV from block and pan using a plastic scraper and solvent. The mating surface must be flat and clean. Lightly scuff with Scotch-Brite if needed; clean with brake cleaner.
- Inspect block mating flange for damage, corrosion, or stripped bolt holes.

8) Prepare new gasket / sealant
- If your 4Runner uses a molded rubber gasket, install it per OEM instructions (some use a small bead of RTV at corners).
- If the factory uses RTV only, apply a continuous bead of the specified Toyota RTV (or equivalent) in the pattern the manual shows — typically a zigzag line around bolt holes. Don’t overdo it; too much will squeeze into the pan and might clog pickup.
- Some pans use a gasket + a light bead of RTV at certain sections — follow the factory method.

9) Install windage tray/pickup if removed
- Replace pickup o-ring/gasket if present. Torque pickup bolts to spec.
- Make sure pickup is fully seated and the screen is not touching the block.

10) Position and install the pan
- Raise pan into position, align dowels, and hand-start bolts in the correct pattern (don’t force). Replace any crushed washers or special bolts.
- Tighten bolts finger-tight, then torque in a crisscross pattern to specified torque in stages. Typical pan bolt torque ranges are low (e.g., ~8–12 ft‑lb / 10–16 N·m) but check the manual. Over‑torquing will distort the pan or strip threads.

11) Drain plug
- Install drain plug with new crush washer and torque to spec (typical range ~20–30 ft‑lb, but check manual).

12) Reinstall removed components
- Reinstall crossmembers, shields, exhaust heat shields, skid plate, etc. Torque bolts to spec.

13) Refill with oil and install filter
- Replace oil filter with new one, pre-lubricate gasket, tighten per spec.
- Fill with the correct type/amount of oil for your engine (check manual).
- Reconnect battery if disconnected.

14) Start engine and check
- Start engine and observe for leaks around pan and drain plug. Let it idle and check oil pressure light behavior.
- Let engine reach operating temperature; re-check for leaks.
- After cool down, re-torque pan bolts if manual calls for it (some require re-torque after initial run, some don’t).
- Check oil level and top up to the correct level.

Common pitfalls and how to avoid them
- Relying only on the jack: always use stands.
- Not replacing crush washer: leads to slow leaks.
- Scratching/block damage when removing old gasket: use plastic scraper; avoid gouging mating surfaces.
- Using too much RTV: excess can squeeze into oil passages/pickup causing blockage.
- Using the wrong gasket method: some models require only RTV, some a molded gasket; use OEM guidance.
- Cross-threading bolts / over-tightening: start bolts by hand and torque to spec in sequence.
- Not replacing pickup O-ring/screen when damaged: can cause air to be drawn into pump leading to low oil pressure.
- Not cleaning the mating surfaces thoroughly: will lead to leaks.

Troubleshooting leaks after reassembly
- If you see a drip directly below a bolt hole: suspect a pinhole or misplaced RTV or a bolt that’s not torqued properly. Re-tighten to spec, then if still leaks, remove and clean, inspect bolt hole threads, replace gasket or re-seal properly.
- If oil leaks from corners: often inadequate RTV bead or wrong gasket placement.
- If oil pressure is low after reassembly: check pickup seating and screen for blockage; ensure oil pump bolts are secure; check for metal debris inside pan (indicator of internal wear).

When to call a pro / red flags
- Significant metal shavings or chunks in the pan — engine damage likely.
- Stripped block threads that prevent proper torque (you may need thread inserts or professional repair).
- A cracked block or pan that requires welding/replacement beyond basic bolt-on work.
- Inability to remove corroded/stuck bolts without breaking them — broken bolts inside the block are hard and time-consuming to extract.

Estimated time & cost (very general)
- Time: 1–4 hours for a typical gasket/pan swap if no complications; longer if crossmember/exhaust removal or internal inspection/repairs.
- Costs: gasket or pan –0 (used vs OEM), oil/filter –, RTV –, replacement bolts/crush washer small additional cost. Labor if pro: 1–4 hours.

Final checklist before driving
- All bolts torqued to spec.
- Drain plug installed with new crush washer.
- Oil filter installed and tightened appropriately.
- Oil filled to correct level.
- No loose tools/clamps under vehicle.
- No leaks after test run.

Closing, short recap
- The oil pan stores oil, the pickup draws it up; leaks or damage require removing the pan, inspecting the pickup and windage tray, cleaning and resealing the mating surfaces, and reassembling with correct parts and torque. Work safely, use jack stands, follow factory sealing method (gasket vs RTV), and consult the factory service manual for model‑specific torque values and procedures.

No questions from me per your instruction — follow the steps above and consult your 4Runner’s service manual for exact bolt counts and torque specs for your model and engine.
rteeqp73

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1) Quick theory — how the clutch hydraulic system works
- The clutch master cylinder (MC) converts pedal travel into hydraulic pressure. Pushrod → piston in MC → pressurized brake fluid in lines → slave cylinder (or concentric slave) moves the clutch release mechanism.
- Proper operation requires: an intact piston/bore and seals to hold pressure, and a system free of air. Air compresses so the pedal feels spongy and pressure is lost; leaks (external or internal) reduce or eliminate ability to generate pressure.
- Common MC faults: worn or scored bore, hardened or torn seals (internal leakage), or contaminated/old fluid causing seal damage. Symptoms: low or sinking pedal, spongy pedal, difficulty disengaging clutch, fluid loss (external leak), or no visible leak (internal bypass).

2) Before you begin (parts, tools, safety) — why each matters
- Parts: correct replacement master cylinder (OEM or equivalent), fresh DOT spec brake/clutch fluid as Toyota specifies. Old fluid carries water and contaminants that damage seals.
- Tools: basic hand tools, line wrench for hydraulic fitting, container for fluid, tube for bleeding, bleeder tool or helper, gloves, rags. Use a line wrench to avoid rounding fittings.
- Safety: work on a cold engine, parking brake on, wheels chocked. Prevent fluid contact with paint (it’s corrosive). Proper disposal of old fluid.
- Why: correct parts ensure proper bore/fit and new seals; correct fluid ensures seal compatibility and hydraulic properties.

3) Diagnosis confirmation (brief)
- Verify pedal behavior: if pedal sinks while held and there’s no external leak, MC internal seals likely failing. If fluid visible at firewall or under vehicle near MC/slave, that’s external leak. Confirm reservoir level and inspect lines/fittings for seepage.
- Why: distinguishing internal vs external leak guides whether replacing MC will fix it (external slave or line leak might need different part).

4) Removal — ordered steps with theory
1. Open reservoir cap and cover it cleanly to prevent dirt entry. Remove excess fluid with a turkey baster or syringe to limit spillage.
- Why: reducing fluid prevents a big spill and contamination.
2. Disconnect negative battery terminal if needed for access/clearance (optional).
- Why: prevents accidental electrical issues if working near wiring.
3. From engine bay, locate master cylinder on the firewall (attached to clutch pedal pushrod). Clean around area.
- Why: prevents dirt contaminating the new system.
4. Place catch container under the hydraulic line at the master-to-line fitting. Use a line wrench to loosen the hydraulic line and cap or plug the line to limit air entry if you can. Remove the hard line fitting.
- Why: minimizes fluid loss and air entry; loosening with a line wrench avoids rounding the nut.
5. Inside the cabin, disconnect the pushrod from the clutch pedal (pin/clip). Remove any retaining pin or clip.
- Why: frees master cylinder for removal without stressing pedal assembly.
6. Unbolt the master cylinder mounting bolts at the firewall and withdraw the MC. Keep the reservoir if reused or remove it if integral.
- Why: physical removal required to replace the failed unit.

5) Bench-prep and bench-bleeding the new master — why critical
- Before installation, fill the new MC reservoir with clean fluid and bench-bleed the MC: attach short hoses from the outlet ports back into the reservoir and slowly depress the piston until you see no air bubbles. Repeat until only clear fluid returns.
- Why: new cylinders contain trapped air. If not bench-bled, that air will be driven into the system and make bleeding very hard; bench-bleeding ensures the MC itself is free of air and its seals are initially lubricated.

6) Installation — ordered steps with theory
1. Mount the new MC to the firewall and tighten bolts to factory torque (refer to service manual).
- Why: correct torque ensures a good mounting and prevents leaks or distortion.
2. Reconnect the pushrod to the clutch pedal at the correct free-play/adjustment (if adjustable); ensure pin/clip is secure.
- Why: correct pedal free play ensures proper disengagement and prevents pre-load of the MC piston.
3. Reattach the hydraulic line to the MC using the line wrench; tighten to proper torque. Make sure fittings and any crush washers/seals are clean and replaced if necessary.
- Why: a properly sealed line prevents external leaks; crush washers provide leak-free connection.
4. Refill reservoir to recommended level with correct DOT fluid. Keep reservoir cap loosely on but not tight to allow venting during bleeding.

7) System bleeding — ordered steps and theory
- Goal: remove all air from lines and slave so only incompressible fluid remains. Air causes spongy pedal and loss of force.
Choose one method:
A. Two-person pump-and-hold: Have helper pump pedal 8–10 times and hold depressed. Open slave bleeder nipple to let fluid/air out, then close bleeder, then helper releases pedal. Repeat until clear fluid no bubbles and pedal firm.
B. Vacuum or pressure bleeder: Connect vacuum pump to slave bleeder or pressure to reservoir and cycle until no bubbles. This is faster and often more reliable, especially with concentric slaves.
- Sequence: always open bleeder at the slave while depressurizing the system. Keep reservoir topped up to avoid introducing new air.
- Why: air must be expelled from the lowest point (slave). Pump-and-hold forces fluid and trapped air toward the bleeder; vacuum/pressure pulls air out without relying on pedal feel.

8) Checks after bleeding — why each matters
- Hold pedal at mid-travel for 30–60 seconds; if it sinks, there’s still internal leakage (bad MC or leak). If it holds firm, pressure integrity is restored.
- Inspect all fittings and seals for leaks under pressure (pedal depressed).
- Verify clutch disengages/engages correctly by starting engine and trying to shift (with chocks and parking brake).
- Why: ensures the repair fixed the pressure-holding function and there are no remaining leaks or air.

9) How the repair fixes the fault — concise theory
- Replacing the MC swaps in a new piston/bore and seals. If the original failed because of worn or torn seals or a scored bore, the new unit restores a smooth bore and tight seals so hydraulic pressure can be generated and held. Bench-bleeding and system bleeding remove air and old contaminated fluid, restoring incompressible fluid column between pedal and slave. Together these eliminate internal bypass (pedal sinking) and external leaks, restoring pedal firmness and clutch actuation.

10) Final notes and cautions
- Use only the correct DOT fluid specified by Toyota (wrong fluid can swell or shrink seals).
- Dispose of old fluid responsibly.
- If leaks were from slave-cylinder or lines instead, replacing MC may not fix the issue—check all components during inspection.
- Refer to factory torque specs and bleeding sequence for your model year for exact values/procedures.

End.
rteeqp73