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Mitsubishi 4D56 engine factory workshop and repair manual download

Tools & consumables
- Safety: safety glasses, nitrile gloves, welding/respirator mask if cutting, ear protection.
- Lifting: hydraulic floor jack, jack stands (rated), wheel chocks, ramps (optional).
- Hand tools: metric socket set (8–24 mm), deep sockets, ratchet, breaker bar (3/8" & 1/2"), extensions, crowfoot for tight spots.
- Wrenches: combination wrenches (8–22 mm).
- Specialty: oxygen (O2) sensor socket or 22 mm open socket with slot, exhaust hanger removal tool, pry bar, flat screwdriver, hammer.
- Penetrants/cleaning: PB Blaster / penetrating oil, wire brush, emery cloth.
- Cutting/removal: reciprocating saw with metal blade or angle grinder + cutoff wheel (for seized bolts).
- Fastening: torque wrench (range to ~150 Nm), impact gun (optional, use cautiously).
- Consumables/replacement parts: new exhaust gaskets (manifold-to-downpipe, downpipe-to-mid-pipe), new flange bolts/nuts or studs (recommended), exhaust clamps, rubber hangers if worn, anti-seize compound (high-temp), high-temp exhaust gasket sealant (only where specified).
- Optional: heat shield fasteners, underbody cleaner, replacement O2 sensor or O2 sensor gasket if removed/damaged.

Safety & prep
1. Work only when the engine and exhaust are cold. Exhaust components retain heat for hours.
2. Park on level ground, engage parking brake, chock rear wheels.
3. Disconnect the negative battery terminal to avoid accidental shorts when removing sensors.
4. Raise vehicle using jack points and secure on jack stands. Never work under a vehicle supported only by a jack.
5. Wear eye protection and gloves. Use respirator when cutting/grinding rusty metal.

Step-by-step: remove and replace exhaust pipe (downpipe/midpipe/tailpipe) — Mitsubishi 4D56
Note: adapt steps to which pipe section you’re replacing (downpipe = turbo/downpipe flange; mid/tail pipe toward rear). Follow sequence below.

1. Access & inspection
- Inspect hangers, clamps, flanges and locate all flange/bolt points and O2 sensors.
- Spray penetrating oil on all nuts/bolts, studs and hangers; let soak 10–20 minutes.

2. Remove O2 sensors and heat shields
- Remove any heat shields bolted to the exhaust section first to improve access.
- Use an O2 sensor socket to remove sensors. Turn counterclockwise. Protect sensor wiring with tape.
- If sensor is seized, apply penetrating oil, heat gently (outside vehicle) or use penetrating heating carefully. Replace sensor if damaged.

3. Support the exhaust
- Support the pipe to be removed with a transmission jack, floor jack with wood pad or a helper. This prevents sudden drop when bolts are removed.

4. Unbolt flange connections
- Start from the rear-most flange and work forward. Use breaker bar for stubborn nuts; use impact gun only if you can control torque and not damage studs.
- If flange nuts are heavily corroded and won’t budge, cut the nut off with a grinder or reciprocating saw, or cut the bolt/stud (be mindful of nearby components). If a stud breaks, you’ll likely need to extract and replace it.

5. Remove exhaust clamps and hangers
- Pry rubber hangers off with exhaust hanger tool or screwdriver, supporting the pipe as you go.
- Remove clamps — some clamps are one-time-use; plan to replace rusted clamps.

6. Lower and remove pipe
- Once all connections and hangers are undone, carefully lower the pipe and remove from under the vehicle. Be mindful of weight and residual soot/soot falling out.

7. Inspect mating surfaces & components
- Clean flange faces with wire brush/emery cloth. Remove rust and old gasket material.
- Inspect studs and flanges for warping — replace if severely damaged.
- Replace any worn or damaged hangers, clamps, or the O2 sensor(s).

8. Fit new gaskets & parts
- Install new exhaust gaskets at all flange joints. Do not reuse old gaskets.
- Put anti-seize on new bolts/stud threads (avoid getting on gasket faces).
- If the procedure calls for a specific sealant, use high-temp exhaust gasket sealant sparingly (consult service manual).

9. Reinstall pipe
- Lift pipe into position and loosely install flange bolts/nuts by hand to align.
- Refit hangers and clamps, ensuring proper alignment and adequate clearance from body/fuel lines.
- Tighten flange nuts gradually and evenly in a crisscross pattern where applicable.

10. Torque to spec & final checks
- Torque bolts to manufacturer specs. If exact numbers are unavailable use typical ranges:
- M8–M10 flange bolts: 25–50 Nm
- M12 flange bolts/studs: 50–80 Nm
- Clamp torque depends on clamp type; tighten until secure and no leak but do not crush pipe.
- Reinstall O2 sensors. Apply a thin smear of anti-seize to O2 sensor threads (do not contaminate sensor tip). Torque O2 sensor to spec (~35–45 Nm typical — check manual).
- Reinstall heat shields.
- Lower vehicle, reconnect battery.

11. Test
- Start engine and let idle; check for exhaust leaks at each flange and around clamps/hangers.
- Listen for rattles; re-torque after warm-up and after a short drive (exhaust components can settle).

Tool usage details & tips
- Penetrating oil: spray generously on nuts/studs, wait. Repeat if necessary. Heat+penetrant combination helps free seized bolts.
- Breaker bar: use steady force; avoid shock loading. Use cheater pipe only when necessary and with care.
- Impact gun: effective on rusted bolts but can easily snap studs — back off if you feel binding.
- O2 sensor socket: slips over sensor harness and allows removal without damaging wiring. Use a crowfoot/ratchet if access is tight.
- Hanger removal tool: clips under rubber hanger and pulls it off the peg without tearing.
- Reciprocating saw/cutoff wheel: use only when bolts cannot be freed. Protect wiring/fuel lines and wear full PPE. Cutting can create heat and sparks—stay clear of fuel/vapor sources.
- Wire brush & emery cloth: ensure flanges are flat and clean for a proper seal.

Replacement parts recommended
- New gaskets (every flange removed) — mandatory.
- New flange bolts/nuts or studs if corroded — strongly recommended.
- New exhaust clamps and rubber hangers if worn.
- O2 sensor(s) if seized or wiring damaged.
- If flange or downpipe is severely corroded, replace that section instead of trying to repair.

Common pitfalls & how to avoid them
- Working on a hot exhaust: wait until completely cool.
- Under-supporting the pipe: always support before unbolting to prevent injury/damage.
- Reusing gaskets: leads to leaks; always replace.
- Breaking studs: use penetrating oil, heat, and steady breaker-bar torque; replace studs if any evidence of damage.
- Damaging O2 sensor wiring: use correct socket and protect wiring; replace sensor if you damage threads.
- Insufficient clearance: ensure pipe is not touching body panels or heat-sensitive lines; adjust hangers/clamps.
- Over-tightening clamps/bolts: can crush pipe or strip threads; use torque wrench.
- Not checking for leaks after install: always inspect and re-torque after warm-up.

Final note
- Exact bolt torque and part numbers change by year/model. Use a Mitsubishi service manual or parts diagram for your vehicle when available. Follow emissions and safety rules when replacing catalytic components.
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