Complete disassembly, inspection, machining, and rebuild of the 2.5L A25A-FKS inline-4 engine including cylinder head reconditioning, crankshaft inspection, piston ring replacement, and timing system renewal.

Warnings

Tools required

Parts

• Complete gasket set (head, oil pan, timing cover, valve cover) × 1 — Use OEM specification
• Piston ring set (standard or oversized as measured) × 1 — Use OEM specification
• Main bearing set (standard or oversized as measured) × 1 — Use OEM specification
• Rod bearing set (standard or oversized as measured) × 1 — Use OEM specification
• Timing chain kit with guides and tensioner × 1 — Use OEM specification
• Valve stem seals × 16 — Use OEM specification
• Cylinder head bolts (TTY - must replace) × 10 — Use OEM specification
• Connecting rod bolts (TTY - must replace) × 8 — Use OEM specification
• Main bearing cap bolts (TTY - must replace) × 10 — Use OEM specification
• Crankshaft pulley bolt (TTY - must replace) × 1 — Use OEM specification
• Oil pump assembly (if worn) × 1 — Use OEM specification
• Water pump × 1 — Use OEM specification
• Thermostat with gasket × 1 — Use OEM specification
• Oil filter × 1 — Use OEM specification
• Spark plugs × 4 — Use OEM specification
• Camshaft position sensor O-rings × 2 — Use OEM specification
• Oil drain plug crush washer × 1 — Use OEM specification
• RTV silicone gasket maker (Toyota Genuine FIPG) × 2 — Use OEM specification

Fluids

• Toyota Genuine 0W-20 engine oil — 5 qt
• Toyota Super Long Life Coolant (Pink) — 10 qt

Preparation

1. Remove engine from vehicle and mount on engine stand using factory mounting points
2. Clean exterior of engine thoroughly with degreaser to prevent contamination during disassembly
3. Document routing of all wiring harnesses, hoses, and external components with photos before removal
4. Drain all remaining coolant and oil into appropriate containers for disposal
5. Remove all external accessories: alternator, A/C compressor, starter, oil filter, sensors, harnesses, fuel rail, injectors, intake and exhaust manifolds
6. Label all removed parts and bag all fasteners by component to ensure proper reassembly
7. Prepare clean workspace with organized bins for small parts and adequate lighting
8. Have machine shop contact information ready for cylinder head and block machining services

Procedure

1. 1

   Remove valve cover and inspect valve train
   Remove valve cover bolts in reverse of tightening sequence. Lift off valve cover and gasket. Inspect camshafts, rocker arms, and valve springs for wear, scoring, or damage. Rotate engine by hand to TDC on cylinder #1 (camshaft lobes on #1 pointing outward). Mark timing chain to camshaft sprocket positions with paint marker for reference.
   Torque spec

   Cover Bolts16 Nm (12 lb-ft)
2. 2

   Remove timing chain cover and timing components
   Remove crankshaft pulley using holding tool and breaker bar or impact wrench. Use harmonic balancer puller if pulley is tight. Remove timing cover bolts in reverse sequence (note different bolt lengths). Remove timing cover carefully to avoid damaging block surface. Release timing chain tensioner by compressing and inserting pin. Remove tensioner bolt, then tensioner. Remove timing chain guides, then lift timing chain off sprockets with camshaft and crankshaft sprockets. Inspect chain for wear (replace if stretch exceeds 0.5mm over 16 links).
   ⚠Crankshaft pulley bolt is extremely tight (180 Nm). Ensure holding tool is secure before applying force.
   Torque spec

   Crankshaft Pulley Bolt180 Nm (133 lb-ft)

   Cover Bolts16 Nm (12 lb-ft)

   Timing Chain Tensioner Bolt25 Nm (18 lb-ft)

   Timing Chain Guide Bolts12 Nm (9 lb-ft)
3. 3

   Remove camshafts and inspect
   Using camshaft holding tool, remove camshaft bearing cap bolts in reverse of tightening sequence (outward to center pattern), loosening gradually in multiple passes to prevent warping. Remove bearing caps (label them for position). Lift out intake and exhaust camshafts. Measure camshaft journal diameter and lobe height with micrometer. Check bearing clearances with Plastigage (standard clearance: 0.025-0.061mm). Inspect cam lobes for scoring or wear patterns. Replace camshafts if lobe wear exceeds 0.2mm or journals are out of spec.
   Torque spec

   Camshaft Bearing Cap Bolts14 Nm (10 lb-ft)
4. 4

   Remove cylinder head
   Remove cylinder head bolts in reverse of tightening sequence (outward from center), loosening gradually in multiple passes. These are TTY bolts and must be discarded. Use pry points (if provided) to break head gasket seal - do not pry between sealing surfaces. Lift cylinder head straight up and place on clean padded surface with combustion chambers facing up. Remove and discard head gasket. Inspect head surface for warpage using straight edge and feeler gauge - maximum warpage 0.05mm. Send cylinder head to machine shop for valve job, resurfacing, pressure testing, and valve guide inspection.
   ⚠Cylinder head bolts are torque-to-yield and must be replaced with new bolts. Reuse will cause head gasket failure.
   Torque spec

   Cylinder Head Bolts65 Nm (48 lb-ft)
5. 5

   Disassemble cylinder head valve train (if doing valve job)
   Using valve spring compressor, compress each valve spring and remove keepers. Release compressor and remove retainer and spring. Remove valve stem seal using pliers or seal removal tool. Slide valve out through combustion chamber side. Keep valves in order (use numbered rack). Inspect valves for burning, pitting, or bent stems. Measure valve stem diameter and margin thickness. Send head to machine shop with valves for complete valve job including seat cutting, guide inspection/replacement, and resurfacing.
6. 6

   Remove oil pan and oil pump
   Remove oil pan bolts in reverse sequence. Carefully separate oil pan from block (may need to tap gently with plastic mallet). Remove oil pump pickup tube bolts and remove pickup tube. Remove oil pump mounting bolts and remove oil pump assembly. Inspect pump rotors for scoring or wear. Check rotor clearances: tip clearance 0.03-0.09mm, body clearance 0.08-0.14mm. Replace pump if clearances exceed specifications or if any scoring is present on rotors or housing.
   Torque spec

   Oil Pan Bolts12 Nm (9 lb-ft)

   Oil Pump Pickup Tube12 Nm (9 lb-ft)

   Oil Pump Bolts12 Nm (9 lb-ft)
7. 7

   Remove pistons and connecting rods
   Check for ridge at top of cylinder bores. Use ridge reamer to remove any ridge before removing pistons to prevent ring damage. Mark connecting rods and caps with cylinder number and orientation using punch marks. Remove connecting rod bolts (these are TTY and must be discarded). Remove rod caps and push piston/rod assemblies out through top of block. Keep rod caps with their respective rods. Inspect connecting rods for bending, twisting, or cracks using magnetic particle inspection if available. Measure big-end bore diameter and small-end bushing for wear.
   ⚠Connecting rod bolts are torque-to-yield and must be replaced. Mark rod cap orientation before removal to ensure correct reassembly.
   Torque spec

   Connecting Rod Bolts45 Nm (33 lb-ft)
8. 8

   Remove crankshaft and main bearings
   Check crankshaft endplay with dial indicator (specification: 0.06-0.16mm). Mark main bearing caps with position and direction using punch marks. Remove main bearing cap bolts in reverse of tightening sequence (these are TTY and must be discarded). Remove main bearing caps carefully. Lift crankshaft straight up out of block. Remove bearing shells from caps and block, keeping them with their respective positions. Measure crankshaft main and rod journals with micrometer for taper, out-of-round, and undersize. Standard main journal diameter: 49.973-49.986mm. Standard rod journal diameter: 44.978-44.991mm. Taper/out-of-round limit: 0.01mm. Send crankshaft for grinding if journals exceed limits.
   ⚠Main bearing cap bolts are torque-to-yield and must be replaced. Mark cap orientation carefully - reversed caps will cause immediate bearing failure.
   Torque spec

   Main Bearing Cap Bolts75 Nm (55 lb-ft)
9. 9

   Measure cylinder bores and inspect block
   Use cylinder bore gauge to measure each cylinder at three heights (top, middle, bottom) and two directions (parallel and perpendicular to crankshaft). Standard bore diameter: 87.50mm. Taper/out-of-round limit: 0.01mm. Oversize limit: 87.55mm (0.5mm oversize). Check block deck surface for warpage using straight edge and feeler gauge (limit: 0.05mm). Inspect block for cracks using magnetic particle or dye penetrant testing, especially around water jackets and main bearing webs. Send block to machine shop for cylinder honing (standard rebuild) or boring (if cylinders exceed limits or are scored). Have deck resurfaced if warped.
10. 10

    Clean and prepare all components
    Thoroughly clean all components in parts washer or hot tank. Remove all carbon deposits from piston crowns and ring grooves using ring groove cleaner. Clean oil passages in block and crankshaft with rifle brush and compressed air. Clean all bolt holes with tap or thread chaser. Ensure all gasket surfaces are completely clean and free of old gasket material or RTV. Clean main and rod bearing bores with lint-free cloth and solvent. Blow out all oil passages with compressed air and verify they are clear. Inspect all threaded holes for damage and repair with thread inserts if necessary.
    ⚠All oil passages must be completely clean and verified clear. Blocked passages will cause oil starvation and rapid bearing failure.
11. 11

    Install new main bearings and crankshaft
    Inspect new bearing shells for correct size marking (standard or undersized to match machined crank journals). Install upper bearing shells into block saddles (align oil hole in bearing with hole in block). Install lower bearing shells into main caps (thrust bearing in center position). Lubricate bearings liberally with assembly lube or clean engine oil. Carefully lower crankshaft into block. Install main bearing caps in correct positions with arrows pointing toward front of engine. Install new TTY main bearing cap bolts hand tight. Torque main cap bolts to 75 Nm in sequence from center outward, then tighten additional 90 degrees in same sequence. Check crankshaft rotates freely by hand. Re-check endplay with dial indicator.
    ⚠Use only new TTY main bearing cap bolts. Tighten in correct sequence: initial torque pass, then 90-degree angle turn in same sequence.
    Torque spec

    Main Bearing Cap Bolts75 Nm (55 lb-ft)
12. 12

    Prepare and install pistons
    Remove old piston rings using ring expander tool. Clean ring grooves thoroughly. Check piston ring end gap by placing ring in cylinder bore (square it with piston) and measuring with feeler gauge. Specification: top ring 0.20-0.35mm, second ring 0.35-0.50mm, oil ring 0.15-0.50mm. Install new rings using ring expander, starting with oil ring (expander first, then rails), then second compression ring (mark facing up), then top compression ring (mark facing up). Stagger ring end gaps 120 degrees apart, avoiding piston pin axis and thrust direction. Install new rod bearings in rods and caps. Lubricate bearings, piston skirts, and rings with assembly lube.
13. 13

    Install piston and rod assemblies
    Ensure piston ring gaps are staggered correctly. Compress rings using ring compressor. Orient piston with front mark toward front of engine. Insert rod bearing into cylinder bore, guiding rod onto crankshaft journal carefully to avoid bearing damage. Push piston into bore using wooden hammer handle while ensuring rings enter bore squarely. Install rod cap in correct orientation (matching marks made during disassembly). Install new TTY connecting rod bolts and torque to 45 Nm, then tighten additional 90 degrees. Ensure rod has slight side-to-side movement on journal. Repeat for all four cylinders. Rotate crankshaft by hand to verify smooth rotation without binding.
    ⚠Use only new TTY connecting rod bolts. Do not allow rod to contact crankshaft journal during installation - bearing damage will occur.
    Torque spec

    Connecting Rod Bolts45 Nm (33 lb-ft)
14. 14

    Install oil pump and oil pan
    Install new or inspected oil pump with new gasket. Torque oil pump bolts to specification. Install oil pump pickup tube with new O-ring, ensuring tube is properly seated in pump. Torque pickup tube bolts to specification. Clean oil pan and block mating surfaces thoroughly. Apply thin continuous bead of Toyota FIPG or equivalent RTV sealant to oil pan flange (3-4mm bead width). Install oil pan within 15 minutes of applying sealant. Install oil pan bolts and tighten in sequence from center outward to specification. Allow sealant to cure for minimum 2 hours before adding oil.
    ℹ️Oil pan must be installed within 15 minutes of applying RTV sealant. Do not start engine until sealant has cured for minimum 2 hours.
    Torque spec

    Oil Pump Bolts12 Nm (9 lb-ft)

    Oil Pump Pickup Tube12 Nm (9 lb-ft)

    Oil Pan Bolts12 Nm (9 lb-ft)
15. 15

    Reassemble cylinder head valvetrain
    Install new valve stem seals on valve guides using seal installation tool (tap gently until seated). Lubricate valve stems with assembly lube. Install valves through combustion chamber side into guides. Install valve springs with closer-pitch coils toward head. Install retainers. Compress springs with valve spring compressor and install keepers in valve stem grooves. Release compressor and tap valve stem lightly to ensure keepers are seated. Verify valve spring installed height is within specification. Repeat for all 16 valves.
16. 16

    Install cylinder head
    Verify block deck surface is clean and dry. Install new head gasket on block with orientation marks facing up and toward front of engine. Carefully lower cylinder head onto block, guiding it over alignment dowels. Install new TTY cylinder head bolts with light oil on threads. Tighten head bolts in sequence from center outward in three passes: first pass to 30 Nm, second pass to 65 Nm, then final pass tighten additional 90 degrees + 45 degrees (total 135 degrees angle turn). Do not rotate crankshaft until camshafts are installed and timed.
    ⚠Cylinder head bolts are TTY and must be new. Tighten in precise sequence with three-step procedure: 30 Nm, 65 Nm, then 135 degrees total angle turn.
    Torque spec

    Cylinder Head Bolts65 Nm (48 lb-ft)
17. 17

    Install camshafts and time to crankshaft
    Rotate crankshaft to TDC on cylinder #1 (keyway at 12 o'clock). Lubricate camshaft journals and lobes with assembly lube. Install intake and exhaust camshafts in their respective positions with timing marks visible. Install camshaft bearing caps in correct positions and orientation (marked during disassembly). Install camshaft cap bolts and tighten in sequence from center outward in three passes: 1st pass finger tight, 2nd pass 7 Nm, 3rd pass to final torque of 14 Nm. Verify camshafts rotate smoothly by hand.
    Torque spec

    Camshaft Cap Bolts14 Nm (10 lb-ft)
18. 18

    Install timing chain system
    Install crankshaft timing sprocket with timing mark visible. Install camshaft timing sprockets loosely. Route new timing chain over crankshaft sprocket, then up and around both camshaft sprockets, aligning timing marks on chain with sprocket marks (verify against marks made during disassembly or service manual diagram). Install timing chain guides and torque bolts. Compress new timing chain tensioner using soft-jawed vise and insert retaining pin. Install tensioner and torque bolt. Remove tensioner pin to apply tension. Verify all timing marks align correctly. Rotate crankshaft two complete revolutions and re-verify timing marks align at TDC.
    ⚠️Verify timing marks are correctly aligned before proceeding. Incorrect timing will cause immediate valve-to-piston contact and catastrophic engine damage when started.
    Torque spec

    Timing Chain Guide Bolts12 Nm (9 lb-ft)

    Timing Chain Tensioner Bolt25 Nm (18 lb-ft)
19. 19

    Install timing cover and crankshaft pulley
    Clean timing cover and block mating surfaces thoroughly. Apply continuous bead of Toyota FIPG sealant to timing cover mating surface. Install timing cover within 15 minutes, ensuring alignment with dowel pins. Install timing cover bolts (note different lengths) and tighten in sequence to specification. Clean crankshaft pulley bolt hole threads. Install crankshaft pulley, aligning keyway. Install new TTY crankshaft pulley bolt. Using holding tool, torque pulley bolt to 180 Nm. Allow sealant to cure minimum 2 hours.
    ℹ️Crankshaft pulley bolt is TTY and must be new. Requires substantial torque (180 Nm) - use holding tool and long breaker bar or impact wrench.
    Torque spec

    Cover Bolts16 Nm (12 lb-ft)

    Crankshaft Pulley Bolt180 Nm (133 lb-ft)
20. 20

    Install valve cover and external components
    Install new valve cover gasket in cover groove. Apply small dab of sealant at camshaft cap corners. Place valve cover on head and install bolts. Tighten valve cover bolts in sequence from center outward to 10 Nm. Install all external components in reverse order of removal: exhaust manifold with new gasket and anti-seize on studs (torque nuts hot-to-cold), intake manifold with new gasket, fuel rail and injectors with new O-rings, all sensors with new O-rings/seals, starter, alternator, A/C compressor, accessory drive belt, harnesses, hoses, and coolant passages. Install new oil filter and oil drain plug with new crush washer.
    Torque spec

    Cover Bolts16 Nm (12 lb-ft)

    Exhaust Manifold Nuts30 Nm (22 lb-ft)

    Intake Manifold Bolts25 Nm (18 lb-ft)

    Oil Drain Plug35 Nm (26 lb-ft)

    Sensor Bolts11 Nm (8 lb-ft)

Reassembly

1. Install engine back into vehicle following reverse of removal procedure
2. Reconnect all engine mounts, torquing mount bolts per specification (note two different mount bolt torque values: 27 Nm and 47 Nm depending on location)
3. Reconnect all wiring harnesses, vacuum lines, coolant hoses, and fuel lines
4. Install serpentine belt and verify proper routing and tension
5. Fill cooling system with 10 quarts Toyota Super Long Life Coolant (pink) and bleed air from system per factory procedure
6. Fill engine with 5 quarts Toyota Genuine 0W-20 engine oil
7. Double-check all connections, bolts, and hose clamps before initial start

Verification

• Perform initial engine start following proper break-in procedure: start engine and allow to idle for 30 seconds, shut off for 1 minute, repeat 5 times to allow rings to seat gradually
• Check for oil leaks around pan, timing cover, valve cover, and all gasket surfaces with engine running
• Check for coolant leaks at all hose connections and gasket surfaces
• Verify oil pressure reaches normal operating range (typically 40-60 PSI at 3000 RPM when warm)
• Monitor engine temperature and verify thermostat opens properly and cooling fans cycle normally
• Listen for any unusual noises: ticking, knocking, or rattling that could indicate improper assembly
• Check for exhaust leaks at manifold gasket and connections
• Perform initial timing verification with scan tool to ensure camshaft and crankshaft correlation is correct
• Drive vehicle gently for first 500 miles: avoid full throttle, vary RPM, avoid sustained high RPM. Change oil and filter at 500 miles to remove break-in debris
• After 500-mile break-in period, perform normal oil change intervals and monitor oil consumption for first 3000 miles

More procedures for this vehicle