Tools needed
- Metric socket set (6–24 mm), extensions, ratchet, breaker bar
- Torque wrench (range to at least 100 Nm) and (if required) angle gauge
- Combination wrenches (including small sizes for adjuster locknuts)
- Feeler gauges (metric set, 0.05–0.50 mm)
- Screwdriver set, pick, pliers
- Rubber/nylon mallet, small pry bar
- Gasket scraper / razor blade, shop rags, solvent
- Torque-to-yield bolt replacement (if specified) / thread locker (per OEM)
- Magnetic tray / parts organizer, marker or tape
- Caliper or micrometer (for measuring shims/parts)
- Engine assembly lube / clean engine oil
- Replacement parts: valve cover gasket, rocker arm(s) or rocker shaft assembly, bushings/bearings, adjuster screws & locknuts or shims (as required), replacement bolts if OEM calls them single‑use
- Jack and axle stands (only if vehicle must be raised)
- Safety gear: gloves, eye protection

Safety precautions
- Work with the engine cold. Hot aluminum heads can cause burns and softening of gaskets.
- Disconnect negative battery terminal.
- Park on level ground, apply handbrake, chock wheels. Use jack stands if vehicle is raised.
- Keep flames/sparks away from open oil areas. Use good ventilation.
- Keep parts clean and organized; contamination of valve train causes premature wear.

Notes up front (important)
- Toyota Hilux engines vary (petrol SOHC/DOHC and diesel OHV/DOHC). Some use hydraulic lash adjusters (no clearance adjustment required) and some use screw‑type or shim‑under‑bucket systems. This procedure covers general removal, inspection, replacement and both common adjustment methods. Always confirm exact specs and torque sequence from the factory workshop manual for your engine and model year.

Procedure — removal and access
1. Preparation
- Remove negative battery cable.
- Drain or remove intake ducting/airbox and any engine covers obstructing valve cover access.
- Remove ancillary items (ignition coils or spark plug leads, vacuum lines, fuel lines over the cover) as needed to access the valve cover. Label connectors.

2. Remove valve cover
- Loosen and remove valve cover bolts in a criss‑cross pattern to avoid warping.
- Pry the valve cover off carefully; if stuck, use a gentle pry at the gasket seam. Do not gouge sealing surface.
- Remove valve cover gasket; clean mating surfaces thoroughly.

3. Expose rocker arms
- With the cover removed you can see the rocker arms/shaft (or rocker assemblies).
- Rotate engine to the correct position for inspection/adjustment (see adjustment section). If replacing parts, note orientation of rocker arms and any indexing marks; take photos.

Removal of rocker arms / shaft (if replacing)
4. Mark and document
- Label each rocker arm/shaft cap and location (left-to-right sequence). Keep assembly order; many shafts/caps are not interchangeable.
- If assembly has a locating dowel or numbered caps, keep them in place order.

5. Loosen saddle/cap bolts progressively
- Loosen bolts one turn at a time across the caps in sequence to relieve stress evenly.
- Remove bolts and caps. Keep caps with their original positions and orientation.

6. Remove rocker shaft and arms
- Carefully lift the rocker shaft assembly out. Some engines have individual rocker arms; remove them individually.
- Inspect pushrods (if present) — roll them on a flat surface to check straightness.

Inspection
7. Inspect components
- Rocker arms: check the contact surface (with valve tip and cam lobes) for pitting, scoring, flattened lobes, or excessive wear.
- Shaft: check for scoring, ovality, wear marks.
- Bushings/bearings: check for play and wear.
- Pushrods: check straightness and tip wear.
- Valves and valve stem tops: check for mushrooming.
- If hydraulic lifters: check they are not collapsed/leaking oil; they may need replacement.

Replacement parts required
- Replace any rocker arms or shafts with visible wear or play.
- Replace bushings/bearings if worn.
- Replace valve cover gasket and any crush washers or seals disturbed.
- Some OEM bolts (especially on newer Toyotas) are single-use/tension bolts — replace if specified in manual.
- Replace adjuster screws, locknuts, or shims as needed to obtain correct clearances.

Reinstallation
8. Clean and lubricate
- Clean all mating surfaces; ensure no old gasket material remains.
- Use assembly lube or clean engine oil on rocker contact surfaces, shafts, and cam lobes (if applicable) during reassembly.

9. Install rockers/shaft and caps in original order
- Place rocker arms/shaft back in original orientation with caps in their matching positions.
- Hand-start bolts, then tighten in the specified sequence progressively to the factory torque. If manual says torque in stages (e.g., 5 Nm → 15 Nm → final), follow it.
- If angle tightening is required, use an angle gauge after initial torque. Do not exceed OEM values.

Valve clearance checking and adjustment
There are three common arrangements: hydraulic lifters (no lash adjustment), screw-and-locknut rockers (adjustable), and shim‑under‑bucket (shim) systems.

A) If your engine uses hydraulic lash adjusters
- No valve clearance adjustment is required under normal conditions. Replace any collapsed/noisy lifters. Reassemble and run.

B) Screw‑and‑locknut rockers (common on many SOHC/OHV engines)
10. Set engine to TDC on the compression stroke for the cylinder you're adjusting (commonly #1 first). Confirm both valves for that cylinder are closed.
11. Use the feeler gauge between the valve stem tip and the rocker face (or as the manual specifies). For screw-style: loosen the adjuster locknut slightly, turn the adjuster screw until the specified clearance is achieved. Technique: insert feeler blade, turn screw until slight drag on blade, hold screw and tighten locknut while keeping screw stationary. Recheck clearance. Repeat for each cylinder in the correct firing order, rotating the engine as required to get each valve on the closed/compression position.
- Feeler gauge use: choose the specified thickness blade; insert between rocker and valve stem; you should feel a slight drag when correct. If too loose, reduce clearance; if too tight, increase.

C) Shim‑under‑bucket systems (DOHC or some modern designs)
12. This requires removal of the camshaft or at least the cam cap to access shims. Follow factory procedure: loosen cam cap bolts in sequence, remove camshaft, keep cam lobes orientation and timing marks.
13. Remove bucket and measure existing gap with feeler gauge. Calculate new shim thickness: new_shim = old_shim + (measured_clearance − spec_clearance). Replace shims with measured value, reassemble camshafts and torque caps per factory sequence. Timing/positioning is critical — do not disturb timing chain/belt or cam timing marks; if you must, re-time per manual.

Final reassembly and checks
14. Install new valve cover gasket and torque cover bolts to spec, in sequence.
15. Reinstall ignition coils, spark plug wires, intake components, battery negative cable.
16. Prime oil to rocker area: crank engine without starting for a few seconds (or follow manual) to circulate oil.
17. Start engine and let idle. Listen for unusual noise (ticking or knocking). Re‑check for oil leaks around the valve cover.
18. Re-check valve clearance after initial run if specified by manual (some designers require re-check after warm-up).

How each tool is used — quick guide
- Torque wrench: use to final-tighten cap bolts and valve cover bolts. Pre‑tighten by hand, then apply torque in prescribed incremental steps and sequence. Use calibrated wrench and appropriate socket.
- Feeler gauge: insert between valve stem tip and rocker (or bucket) when valve is fully closed. There should be a slight drag on the blade when correct. For screw adjusters, hold screwdriver on adjuster and one wrench on locknut while tuning.
- Breaker bar/ratchet: initial loosening of caps/valve cover bolts. Use care to avoid rounding bolt heads.
- Micrometer/caliper: measure old shims and verify new shim thickness if doing shim change.
- Gasket scraper/solvent: clean sealing surfaces to prevent oil leaks.

Common pitfalls and how to avoid them
- Not confirming engine is on compression stroke for the cylinder when adjusting — leads to wrong lash. Rotate to TDC compression with both valves closed.
- Mixing up or reversing caps/rocker arms — mark and keep original orientation.
- Reusing torque‑to‑yield or single‑use bolts — can lead to failures; replace as manufacturer requires.
- Over‑tightening or under‑tightening cap bolts — causes bearing distortion or movement; always use correct torque and sequence.
- Not cleaning mating surfaces — leads to oil leaks.
- Not lubricating contact surfaces on reassembly — causes premature wear on initial start.
- Losing or mixing shims — label and measure every shim; keep organized.
- For DOHC/shim systems: removing camshafts without marking timing — leads to incorrect timing and severe engine damage. If cam timing is disturbed, follow factory timing procedure.
- Adjusting cold when the specification is for warm (or vice versa) — follow the spec temperature condition.
- Forgetting to recheck clearance after run-in when manual requires it.

When to replace parts
- Replace any rocker with pitting, flattened contact surface, or excessive play.
- Replace shaft/bushings if scoring or wear beyond service limits.
- Replace hydraulic lifters if they are noisy or collapsed (measured/compared).
- Replace valve cover gasket whenever the cover is removed.
- Replace any bolts called out as non‑reusable in the workshop manual.

Closing
Follow the factory workshop manual for exact valve clearances, torque values, bolt sequences and any engine‑specific procedures. Proper labeling, cleanliness, correct tooling (torque wrench, feeler gauges), and following sequence/torque steps are the keys to a successful rocker arm service.
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