Complete replacement of the engine short block assembly, including removal of cylinder head, oil pan, timing components, and all internal rotating assembly while leaving the vehicle-mounted long block components intact.

Warnings

Tools required

Parts

• Short block assembly (2.5L A25A-FKS) × 1 — Use OEM specification
• Cylinder head gasket × 1 — Use OEM specification
• Oil pan gasket × 1 — Use OEM specification
• Timing chain cover gasket × 1 — Use OEM specification
• Oil pump O-ring × 1 — Use OEM specification
• Main bearing set × 1 — Use OEM specification
• Connecting rod bearing set × 1 — Use OEM specification
• Piston ring set × 1 — Use OEM specification
• Oil pump assembly × 1 — Use OEM specification
• Oil filter × 1 — Use OEM specification
• Oil drain plug crush washer × 1 — Use OEM specification
• Crankshaft pulley bolt × 1 — TTY - Use OEM specification
• Main bearing cap bolts × 10 — TTY - Use OEM specification
• Connecting rod bolts × 8 — TTY - Use OEM specification
• Flywheel bolts × 8 — TTY - Use OEM specification
• RTV silicone sealant (Toyota Genuine) × 1 — Use OEM specification

Fluids

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

Preparation

1. Position vehicle on level surface and engage parking brake
2. Disconnect negative battery terminal and wait 90 seconds for airbag system discharge
3. Drain engine coolant completely into appropriate container
4. Drain engine oil completely and remove oil filter
5. Remove engine cover and air intake system
6. Remove accessory drive belt
7. Support engine securely from above using engine hoist or support fixture
8. Remove right-side engine mount to allow engine tilt access
9. Label and photograph all electrical connectors and vacuum lines before disconnection
10. Document timing chain alignment marks before disassembly

Procedure

1. 1

   Remove cylinder head assembly
   Disconnect all fuel lines, coolant hoses, and electrical connections from cylinder head. Remove exhaust manifold and intake manifold assemblies. Remove valve cover. Follow proper cylinder head bolt loosening sequence (reverse of installation pattern, working from outside to inside in multiple passes). Lift cylinder head assembly off block and place on clean workbench. Remove and inspect head gasket.
2. 2

   Remove timing chain and front cover
   Lock crankshaft using flywheel holding tool. Remove crankshaft pulley bolt using breaker bar or impact wrench. Use harmonic balancer puller to remove crankshaft pulley. Remove timing chain cover bolts in reverse sequence. Carefully separate timing chain cover from block (may require gentle prying). Remove timing chain tensioner, guides, and timing chain assembly. Mark or photograph camshaft and crankshaft timing positions before removal.
   Torque spec

   Crankshaft Pulley Bolt180 Nm (133 lb-ft)

   Cover Bolts16 Nm (12 lb-ft)
3. 3

   Remove oil pan and oil pump
   Remove all oil pan bolts in crisscross pattern. Carefully separate oil pan from block using plastic trim tools (do not pry with metal tools). Clean gasket surfaces thoroughly. Remove oil pump mounting bolts and extract oil pump assembly along with pickup tube. Inspect oil pump drive chain and guides.
   Torque spec

   Oil Pan Bolts12 Nm (9 lb-ft)

   Oil Pump Bolts12 Nm (9 lb-ft)
4. 4

   Remove pistons and connecting rods
   Rotate engine so piston to be removed is at bottom dead center. Check connecting rods and caps for cylinder identification marks (mark if not present). Remove connecting rod bolts and caps, keeping matched sets together. Push piston and rod assembly out through top of cylinder bore. Repeat for all four cylinders. Keep all parts organized by cylinder number.
   Torque spec

   Connecting Rod Bolts45 Nm (33 lb-ft)
5. 5

   Remove crankshaft and main bearings
   Check main bearing caps for position marks and orientation arrows (mark if not present). Remove main bearing cap bolts in reverse of tightening sequence. Carefully remove main bearing caps, keeping them in order. Lift crankshaft straight up out of block. Remove upper main bearing shells from block and lower shells from caps. Inspect crankshaft journals for damage or scoring.
   Torque spec

   Main Bearing Cap Bolts75 Nm (55 lb-ft)
6. 6

   Inspect and prepare new short block
   Thoroughly inspect new short block assembly for shipping damage or debris. Verify crankshaft rotates freely by hand. Check all main bearing clearances using Plastigage (should be 0.001-0.002 inches). Verify connecting rod bearing clearances (should be 0.0008-0.0018 inches). Measure piston ring end gaps in cylinders. Confirm all cylinder bores are within specification and properly honed.
7. 7

   Install crankshaft and main bearings
   Clean all bearing surfaces in block and caps with lint-free cloth and solvent. Install upper main bearing shells in block (ensure oil holes align). Lightly oil bearing surfaces with clean engine oil. Carefully lower crankshaft into block. Install lower bearing shells in main caps. Apply light coat of engine oil to bearing surfaces. Install main bearing caps in correct positions with arrows pointing forward. Install NEW main bearing cap bolts. Torque bolts to 75 Nm (55 lb-ft) in proper sequence, then rotate each bolt an additional 90 degrees using torque angle gauge.
   ⚠️Main bearing cap bolts are TTY and must be replaced. Reusing old bolts can cause bearing failure.
   Torque spec

   Main Bearing Cap Bolts75 Nm (55 lb-ft)
8. 8

   Install pistons and connecting rods
   Install piston rings on pistons (oil control ring first, then lower compression ring, then upper compression ring) with gaps properly staggered 120 degrees apart. Lubricate piston rings, piston skirts, and cylinder bores thoroughly with clean engine oil. Install upper connecting rod bearings and lubricate with engine oil. Compress rings with piston ring compressor and carefully tap piston into cylinder bore with hammer handle, ensuring directional marks face forward. Install lower rod bearings in caps, position caps with marks matching rods. Install NEW connecting rod bolts and torque to 45 Nm (33 lb-ft), then rotate an additional 90 degrees. Repeat for all cylinders.
   ⚠️Connecting rod bolts are TTY and must be replaced. Do not reuse old bolts.
   ⚠Ensure piston orientation marks face forward and ring gaps are properly staggered to prevent blow-by.
   Torque spec

   Connecting Rod Bolts45 Nm (33 lb-ft)
9. 9

   Install oil pump and oil pan
   Install new O-ring on oil pump assembly. Prime oil pump by filling with clean engine oil and rotating pump gears by hand. Install oil pump assembly with pickup tube and torque mounting bolts to 12 Nm (9 lb-ft). Clean oil pan and block mating surfaces completely (all old gasket material and RTV must be removed). Apply thin bead of Toyota Genuine RTV silicone to oil pan gasket groove. Install new oil pan gasket. Position oil pan and install bolts finger-tight. Torque oil pan bolts to 12 Nm (9 lb-ft) in crisscross pattern from center outward. Allow RTV to cure per manufacturer instructions before adding oil.
   Torque spec

   Oil Pump Bolts12 Nm (9 lb-ft)

   Oil Pan Bolts12 Nm (9 lb-ft)
10. 10

    Install timing components and front cover
    Install crankshaft timing gear ensuring alignment marks face outward. Install camshaft timing gears (if transferred from old engine). Route new timing chain over crankshaft and camshaft sprockets with alignment marks in proper positions per service manual. Install timing chain guides and tensioner (tensioner compressed/pinned during installation). Clean timing cover and block mating surfaces thoroughly. Install new timing cover gasket or apply RTV per Toyota specifications. Position timing cover and install bolts finger-tight. Torque 8mm timing cover bolts to 25 Nm (18 lb-ft) in proper sequence. Release timing chain tensioner pin. Install crankshaft pulley and NEW crankshaft pulley bolt. Torque pulley bolt to 180 Nm (133 lb-ft).
    ⚠️Crankshaft pulley bolt is TTY and must be replaced with new bolt.
    ⚠Verify timing marks are properly aligned before installing timing cover. Incorrect timing will cause engine damage.
    Torque spec

    Cover Bolts16 Nm (12 lb-ft)

    Crankshaft Pulley Bolt180 Nm (133 lb-ft)
11. 11

    Install cylinder head assembly
    Clean cylinder head and block mating surfaces completely ensuring no debris or old gasket material remains. Inspect block deck for flatness. Position new cylinder head gasket on block (observe all alignment dowels and orientation marks). Carefully lower cylinder head onto block. Install cylinder head bolts and washers (apply clean engine oil to bolt threads and under bolt heads). Torque cylinder head bolts in three stages following proper sequence from center outward: Stage 1 to 22 Nm, Stage 2 to 65 Nm, then Stage 3 rotate each bolt 90 degrees. Reconnect all coolant hoses, fuel lines, and electrical connections.
12. 12

    Install remaining components
    Install valve cover with new gasket, torquing cover bolts to 16 Nm (12 lb-ft) in sequence. Install intake and exhaust manifolds with new gaskets. Reconnect all vacuum lines, electrical connectors, and sensors per documentation from disassembly. Install accessory drive belt. Reinstall engine mount and torque mounting bolts appropriately (27 Nm or 47 Nm depending on location). Install new oil filter. Install oil drain plug with NEW crush washer and torque to 35 Nm (26 lb-ft).
    Torque spec

    Cover Bolts16 Nm (12 lb-ft)

    Oil Drain Plug35 Nm (26 lb-ft)

    Mounting Bolts27 Nm (20 lb-ft)

Reassembly

1. Double-check that all main bearing cap bolts, connecting rod bolts, crankshaft pulley bolt, and flywheel bolts are NEW TTY fasteners
2. Verify all electrical connectors and vacuum lines are properly reconnected per disassembly documentation
3. Ensure all coolant hoses are properly secured with new clamps where needed
4. Verify accessory drive belt is properly routed and tensioned
5. Confirm all ground straps are reconnected

Verification

• Fill engine with 5.0 quarts of Toyota Genuine 0W-20 engine oil
• Refill cooling system with 10.0 quarts of Toyota Super Long Life Coolant (Pink) and bleed air from system
• Reconnect negative battery terminal
• Perform initial start without spark plugs or fuel pump fuse to prime oil system - verify oil pressure gauge shows pressure
• Reinstall spark plugs and fuel pump fuse, start engine and verify oil pressure immediately
• Allow engine to idle and warm to operating temperature while monitoring for leaks, unusual noises, or warning lights
• Check for coolant, oil, and fuel leaks at all connections
• Verify proper engine operation at various RPM ranges
• Perform final torque check on all critical fasteners after engine reaches operating temperature
• Road test vehicle under light load, then recheck all fluid levels and inspect for leaks
• Reset ECU adaptation values and perform any required relearning procedures per Toyota service procedures
• Schedule follow-up inspection after 500 miles for retorque verification and oil/filter change

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