Tools & consumables (minimum)
- Metric socket/ratchet set (8–24 mm), deep sockets, 1/2" drive breaker bar, extensions, universal joint.
- Torque wrench (capable to engine head torque; e.g., 0–200 Nm / 0–150 ft·lb) + torque-angle gauge if bolts are torque‑to‑yield (TTY).
- Impact gun (use only to break fasteners; do NOT final torque with it).
- Box/open wrenches, screwdriver set, pliers.
- Engine hoist or an engine support bar (ZD30 head heavy; use hoist/support).
- Gasket scraper (plastic + razor blade), wire brush, brass/nylon brush.
- Straight edge and feeler gauges (to check warpage).
- Dial caliper or micrometer (optional, for head/block thickness).
- Thread chaser or M12/M14 chase tap (clean bolt holes).
- Valve spring compressor (if removing valves).
- Drain pans, funnels, brake cleaner or parts cleaner, rags, shop vacuum.
- Sealant: OEM-recommended RTV for corners (if specified).
- New head gasket set (complete gasket set for engine), new head bolts (always replace TTY bolts), intake/exhaust manifold gaskets, valve cover gasket, oil pan gasket if disturbed, thermostat gasket, water pump gasket, oil & coolant, oil filter, fuel line/oring kits (diesel injectors), turbo gaskets (if applicable).
- Safety: gloves, safety glasses, jack stands, wheel chocks.

Safety precautions (non-negotiable)
- Work on a level surface, wheels chocked, parking brake on, battery negative disconnected.
- Support vehicle on jack stands if raised; never rely on a jack alone.
- Drain coolant and oil into suitable containers; dispose properly.
- Relieve fuel system pressure (diesel) before disconnecting fuel lines; catch spills and clean immediately.
- Wear eye protection and gloves; avoid ignition sources when working with fuel.
- Label electrical connectors, hoses and vacuum lines; take pictures for reassembly.
- Have an assistant or hoist when lifting heavy parts (head/turbo).

Overview — what we’re doing
- Remove accessories, intake/exhaust, turbo/fuel injectors (as required), timing cover and timing components, then remove cylinder head(s).
- Inspect head and block mating surfaces; measure for warpage; machine if necessary.
- Install new head gasket and new head bolts per factory torque procedure; reassemble ancillary gaskets and components; refill and test.

Step-by-step procedure (generic for head gasket replacement)
1. Preparation
- Disconnect negative battery terminal.
- Drain engine coolant and engine oil.
- Remove air intake piping, intercooler pipes (diesel/turbo), battery tray, radiator fan shroud if needed for access.
- Label and remove electrical connectors, vacuum lines, coolant hoses that obstruct head removal.
- Remove turbo/downpipe (ZD30 frequently), exhaust manifold heat shields, EGR piping if fitted.

2. Fuel system & injectors (diesel note)
- On ZD30 diesel: relieve fuel system pressure, disconnect high-pressure fuel lines to injectors, cap lines to prevent contamination. Remove rocker cover/valve cover to access injectors and upper head fasteners if necessary.
- On KA23DE petrol: remove ignition coils/plugs, fuel rail, throttle body/intake manifold as required.

3. Remove timing components and put engine at TDC
- Rotate engine to Top Dead Center (cylinder 1) and mark timing positions.
- Remove timing cover, loosen timing belt/chain tensioner, remove belt/chain. Mark cam/crank positions thoroughly (take photos).
- Important: do not let camshafts rotate relative to each other after removal if you’re not removing cams — support camshafts.

4. Remove valve cover and any cam journals/cams if required
- Remove rocker arms/cam caps in pattern, keeping parts labeled and in order (if doing a head-off job).
- If you will reuse cams, follow correct loosen sequence to prevent spring-induced distortion.

5. Remove cylinder head
- Remove head bolts in the reverse order of tightening sequence, in several passes to avoid distortion.
- Lift head using hoist or helper; place on clean engine stand or workbench.
- Note: ZD30 head is heavy; use hoist or support bar.

6. Inspect & clean
- Remove old gasket material with plastic scraper and solvent. Avoid gouging surfaces.
- Use thread chaser to clean bolt holes; blow out with compressed air.
- Check head and block mating surfaces with a straight edge and feeler gauges. Standard max warp is small — consult factory manual. If warped beyond spec, machine the head.
- Inspect for cracks (pressure test or magnaflux), burned valves, broken injector seats.
- Check cam journals, bearings, valve guides for wear.

7. Replace parts (recommended)
- Install a new OEM head gasket set. Do NOT reuse head gasket.
- Replace head bolts (TTY) — always new if original are torque-to-yield.
- Replace valve cover gasket, intake & exhaust manifold gaskets, turbo gaskets, thermostat, water pump (recommended if old), oil filter, oil seals if disturbed.
- Replace injector O-rings/seals (diesel) and clean injector bores.

8. Prep mating surfaces & gasket placement
- Ensure surfaces are clean, dry, and oil-free. Use solvent and lint-free rag.
- Place head gasket onto dowels (if provided) in the correct orientation.
- Do not use sealant on head gasket surfaces unless factory manual specifies small dabs in specific locations.

9. Head installation and torquing
- Lower head straight down; ensure correct seating on dowels.
- Insert new head bolts hand-tight.
- Follow factory torque sequence and steps exactly: usually progressive torque (e.g., snug all, then intermediate torque, then final torque or torque-to-angle step). Use torque-angle gauge if required.
- Use torque wrench for all final torques. Do not use impact gun for final torques.

10. Reassemble timing & valvetrain
- Reinstall cams, lifters, rocker arms; set valve clearances if required (KA23DE often requires valve lash check/adjust).
- Reinstall timing belt/chain and tensioner; align timing marks exactly. Rotate engine by hand two full revolutions and re-check TDC/marks.
- If timing components were replaced, torque tensioners to spec.

11. Reinstall manifolds, turbo, fuel system
- Refit exhaust manifold with new gaskets; torque bolts in correct pattern.
- Reattach injectors and fuel lines (diesel: ensure clean and correct torque; prime system).
- Reinstall intake manifold, throttle body, sensors, intercooler pipes.

12. Fluids, bleed & final checks
- Refill engine oil (use new oil and filter) and coolant (use correct mix).
- Reconnect battery.
- Prime fuel system (diesel) per manual to avoid starting difficulties.
- Start engine and monitor for coolant leaks, oil leaks, unusual noises.
- Bring engine to operating temperature; bleed cooling system of air pockets per factory procedure.
- Re-torque head bolts only if manual calls for re-torque after warm-up (many TTY bolts do NOT require re-torque).

13. Test drive & recheck
- After short road/test run, recheck fluid levels and inspect for leaks.
- Recheck timing and idle; adjust valve clearances if necessary.

Engine-specific notes & common pitfalls
- ZD30DD (diesel, heavy head, injectors/turbo):
- Diesel injectors and high-pressure lines must be handled cleanly; replace injector seals and use new copper crush washers on banjos when required.
- Turbo/intercooler pipes removal improves access; be careful with oil return lines.
- Head bolts almost always TTY; do not reuse. Use torque-angle gauge.
- Diesel heads more likely to need bench checks for cracking; pressure test strongly recommended.
- Use hoist or engine support — attempting to lift by hand risks dropping and damaging head.

- KA23DE (petrol):
- Check valve clearances after reassembly; some engines require shims or lash adjustment.
- Timing belt/chain alignment critical; if belt is old, replace water pump/tensioner at same time.
- Cam seals and crank seal inspection; replace as preventative maintenance.

Common mistakes to avoid
- Reusing head bolts that are TTY — leads to head lift and leaks.
- Improperly cleaned or gouged mating surfaces — causes leaks.
- Skipping straight edge/warpage check — overheated engines often need head machining.
- Incorrect torque sequence or angles — leads to uneven clamp and gasket failure.
- Allowing debris into oil/coolant passages or injectors — will damage engine.
- Forgetting to replace small gaskets/seals (thermostat, oil cooler lines, turbo drain) — common leak sources.
- Reassembling timing with marks misaligned — will cause poor running or engine damage.
- Using general RTV everywhere — only use what the manual specifies and in correct spots.

How each critical tool is used (brief)
- Torque wrench: tighten bolts in the specified sequence and in stages; final torque only with torque wrench. If TTY bolts, follow angle turns with torque-angle gauge.
- Straight edge & feeler gauges: lay straight edge across head/block surfaces in multiple directions; slide feeler gauge to detect warpage. If feeler gauge exceeds manual limit, head/block must be machined.
- Thread chaser: clean bolt threads and holes to allow accurate torque readings; do not deepen or alter threads.
- Engine hoist/support: support and lift heavy head; attach to designated lifting points to avoid bending.
- Gasket scraper & solvent: remove old gasket material without gouging aluminum; use plastic scraper first, then razor carefully.
- Valve spring compressor: if removing valves for inspection or reconditioning; compress spring to remove keepers.

Parts checklist to buy before starting
- OEM head gasket set (engine-specific) and TTY head bolts.
- Valve cover gasket set, intake & exhaust manifold gaskets.
- Turbo gaskets/oil return gaskets.
- Thermostat and gasket, water pump (recommended), timing belt/chain tensioner or timing kit if belt-driven.
- Oil, oil filter, coolant, injector O-rings/seals.
- Misc: sealing washer kit for fuel/turbo lines, hose clamps, thread locker as specified.

Final notes
- Always get the factory service manual for exact bolt sequences, torque values, angle specs, valve clearance specs and timing procedures for the ZD30DD and KA23DE — those specs are critical.
- If you are unsure about machining, cribbed bolt torque specs, or diesel injector seating, consult a machine shop or qualified engine rebuilder.

End.
rteeqp73

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