Complete disassembly, inspection, machining, and reassembly of the 2.5L A25A-FKS inline-4 engine including crankshaft, pistons, camshafts, timing chain, and cylinder head.

Warnings

Tools required

Parts

• Complete engine gasket set with head gasket × 1 — Use OEM specification
• Piston ring set (standard or oversized as measured) × 1 — Use OEM specification
• Main bearing set (standard or undersized as measured) × 1 — Use OEM specification
• Rod bearing set (standard or undersized as measured) × 1 — Use OEM specification
• Timing chain kit with guides and tensioner × 1 — Use OEM specification
• Timing chain VVT-i actuators (intake and exhaust) × 2 — Use OEM specification
• Oil pump assembly or rebuild kit × 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
• Valve stem seals × 16 — Use OEM specification
• Cylinder head bolts (TTY - replace) × 1 — Use OEM specification
• Main bearing cap bolts (TTY - replace) × 1 — Use OEM specification
• Connecting rod bolts (TTY - replace) × 1 — Use OEM specification
• Crankshaft pulley bolt (TTY - replace) × 1 — Use OEM specification
• Flywheel bolts (TTY - replace) × 1 — Use OEM specification
• Oil drain plug crush washer × 1 — Use OEM specification
• RTV silicone gasket maker (Toyota Genuine FIPG) × 1 — Use OEM specification

Fluids

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

Preparation

1. Position engine on secure engine stand with 360-degree rotation capability
2. Clean exterior of engine thoroughly with degreaser before disassembly to prevent contamination
3. Organize workspace with separate clean areas for parts storage and assembly
4. Prepare labeled containers for hardware and small parts organization
5. Have factory service manual available for reference specifications and clearances
6. Establish relationship with machine shop for cylinder boring, honing, valve work, and head resurfacing
7. Ensure all replacement parts, gaskets, and fluids are available before beginning reassembly

Procedure

1. 1

   Remove external accessories and manifolds
   Remove alternator, A/C compressor (if still attached), power steering pump mounting bracket, and all remaining accessory brackets. Remove intake manifold assembly and exhaust manifold. Remove all sensors, ignition coils, and wiring harnesses still attached to engine. Label all electrical connectors for reinstallation.
   Torque spec

   Exhaust Manifold Nuts30 Nm (22 lb-ft)

   Intake Manifold Bolts25 Nm (18 lb-ft)
2. 2

   Remove valve cover and timing chain cover
   Remove valve cover by loosening bolts in reverse sequence (outside to center). Clean any remaining oil from cylinder head. Remove crankshaft pulley using harmonic balancer puller or impact wrench. Remove timing chain cover by loosening all 8mm bolts in reverse sequence. Inspect timing cover oil seal and replace during assembly.
   Torque spec

   Cover Bolts16 Nm (12 lb-ft)

   Crankshaft Pulley Bolt180 Nm (133 lb-ft)
3. 3

   Remove timing chain assembly
   Rotate crankshaft to TDC cylinder #1 (timing marks aligned). Remove timing chain tensioner and note compression mechanism. Remove timing chain guides. Mark timing chain relationship to camshaft and crankshaft sprockets with paint marker. Remove VVT-i actuators from camshaft ends. Remove timing chain from sprockets. Inspect chain for wear, elongation, and guide damage.
   Torque spec

   Timing Chain Tensioner Bolt25 Nm (18 lb-ft)

   Timing Chain Guide Bolts12 Nm (9 lb-ft)
4. 4

   Remove camshafts and cylinder head
   Loosen camshaft bearing cap bolts in reverse sequence (outside to center) in multiple passes to prevent warping. Remove camshafts and mark for intake/exhaust identification. Remove cylinder head bolts in reverse of tightening sequence. Lift cylinder head from block and place on clean padded surface. Do not place head gasket-side down. Remove and discard head gasket.
   ⚠Camshaft bearing caps MUST be reinstalled in original positions and orientation. Mark clearly during removal.
   Torque spec

   Camshaft Bearing Cap Bolts14 Nm (10 lb-ft)

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

   Remove oil pan and oil pump
   Drain any remaining oil into appropriate container. Remove oil pan bolts in reverse sequence and carefully separate pan from block using plastic gasket scraper. Remove oil pump pickup tube and oil pump assembly. Inspect oil pump rotors for wear and scoring. Remove balance shaft assembly if equipped.
   Torque spec

   Oil Pan Bolts12 Nm (9 lb-ft)

   Oil Pump Bolts12 Nm (9 lb-ft)

   Oil Pump Pickup Tube12 Nm (9 lb-ft)

   Balance Shaft Bolts25 Nm (18 lb-ft)
6. 6

   Remove pistons and connecting rods
   Using ridge reamer, remove any ridge at top of cylinder bores to prevent ring damage during piston removal. Mark connecting rods and caps with cylinder number and orientation. Remove connecting rod bolts and caps. Push piston and rod assemblies out through top of block. Keep rod caps with their respective rods. Inspect pistons for scoring, cracking, and ring land damage.
   ⚠Protect crankshaft journals by covering with shop rags or rubber hose over rod bolts when removing pistons.
   Torque spec

   Connecting Rod Bolts45 Nm (33 lb-ft)
7. 7

   Remove crankshaft and main bearings
   Mark main bearing caps for position and orientation (they are not interchangeable). Remove main bearing cap bolts in reverse of tightening sequence. Carefully lift main bearing caps and set aside in order. Lift crankshaft from block and place on clean surface. Remove main bearing shells from caps and block, keeping upper and lower pairs together. Inspect crankshaft journals for scoring, discoloration, and out-of-round condition.
   ⚠Main bearing caps must be reinstalled in exact original positions and orientation. Improper installation will cause immediate engine failure.
   Torque spec

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

   Complete disassembly and cleaning
   Remove all freeze plugs and oil gallery plugs from block. If performing valve work, remove valves from cylinder head using valve spring compressor and keep valves in order. Thoroughly clean all components in parts washer with appropriate solvent. Use compressed air to blow out all oil passages and bolt holes. Clean all gasket surfaces with plastic scraper (do not use metal scrapers on aluminum). Chase all bolt threads with thread chaser to remove debris and old thread locker.
9. 9

   Measure and inspect all components
   Measure cylinder bores for taper and out-of-round using dial bore gauge at three levels (top, middle, bottom) in two directions 90 degrees apart. Measure crankshaft journals for taper, out-of-round, and undersize using micrometer. Measure piston-to-bore clearance. Measure crankshaft endplay. Check cylinder head deck surface for warpage using precision straightedge and feeler gauge. Document all measurements and compare to Toyota specifications. Determine machining requirements and bearing/piston sizes needed.
   ℹ️Typical acceptable limits: cylinder taper 0.05mm max, crankshaft journal taper 0.025mm max, head warpage 0.05mm max. Consult factory specifications.
10. 10

    Machine shop services
    Send block to machine shop for cylinder boring and honing (if needed), deck resurfacing (if warped), and hot tank cleaning. Send crankshaft for journal grinding (if needed) and polishing. Send cylinder head for valve job, guide replacement (if needed), seat machining, and deck resurfacing. Send connecting rods for resizing and balance check. Request all components be balanced as matched set if doing performance rebuild.
11. 11

    Install new freeze plugs and gallery plugs
    Install new expansion/freeze plugs in block using appropriate size driver and sealant. Drive plugs in until flush with block surface. Install new oil gallery plugs with thread sealant. Ensure all coolant passages are clean and clear of debris.
12. 12

    Install crankshaft and main bearings
    Install upper main bearing shells into block (without lubrication for Plastigage measurement). Place crankshaft in block. Install lower bearing shells in main caps. Place Plastigage strips on each crankshaft journal. Install main caps in correct position and orientation. Install NEW main bearing cap bolts and torque to 75 Nm (55 lb-ft) plus angle specification per Toyota procedure. Remove caps and measure Plastigage width to verify bearing clearance (typical 0.025-0.045mm). If clearance acceptable, remove Plastigage, lubricate all bearing surfaces with assembly lube, and perform final installation. Torque main caps to 75 Nm plus angle in sequence from center outward. Verify crankshaft rotates smoothly. Measure crankshaft endplay with dial indicator (typical 0.05-0.25mm).
    ⚠Do not rotate crankshaft with Plastigage installed. This will give false readings.
    Torque spec

    Main Bearing Cap Bolts75 Nm (55 lb-ft)
13. 13

    Install pistons and connecting rods
    Install piston rings on pistons using ring expander tool. Position ring gaps per Toyota specification (typically 120 degrees apart, not aligned with pin or thrust side). Verify ring end gap before installation (typical 0.20-0.40mm for compression rings). Lubricate cylinder bores with engine oil. Lubricate piston and rings thoroughly. Install piston ring compressor on piston. Orient connecting rod for correct cylinder and install rod bearing shells. Apply assembly lube to rod bearings. Guide piston into cylinder bore with ring compressor, using wooden hammer handle to tap piston in gently. Guide connecting rod onto crankshaft journal. Install rod cap in correct orientation with NEW connecting rod bolts. Torque rod bolts to 45 Nm (33 lb-ft) plus angle specification per Toyota procedure. Verify rod bearing clearance using Plastigage method if desired. Repeat for all four cylinders. Verify all rods can move freely side-to-side on journals and crankshaft rotates smoothly.
    ⚠Ensure piston orientation is correct with arrow or marking facing timing chain end of engine.
    Torque spec

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

    Install oil pump and oil pan
    Install balance shaft assembly (if equipped) with new bolts torqued to specification. Pack oil pump with petroleum jelly to prime. Install oil pump assembly with NEW bolts torqued to 12 Nm. Install oil pump pickup tube with NEW O-ring and torque to 12 Nm. Clean oil pan and block mating surfaces thoroughly. Apply thin bead of Toyota FIPG RTV silicone to oil pan in continuous bead (3-4mm diameter) around all bolt holes and sealing surfaces. Install oil pan within 3 minutes of RTV application. Install oil pan bolts and torque in sequence from center outward to 12 Nm. Allow RTV to cure per manufacturer specification (typically 30 minutes before oil fill, 4 hours before running).
    Torque spec

    Balance Shaft Bolts25 Nm (18 lb-ft)

    Oil Pump Bolts12 Nm (9 lb-ft)

    Oil Pump Pickup Tube12 Nm (9 lb-ft)

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

    Rebuild and install cylinder head
    If performing valve work, install new valve stem seals on guides using appropriate driver. Install valves in original positions with light oil on stems. Install valve springs, retainers, and keepers using valve spring compressor. Verify keeper seating by tapping valve tip with plastic mallet. Perform valve spring installed height check and valve seal test if equipped. Clean cylinder head and block mating surfaces with brake cleaner. Install NEW cylinder head gasket on block with proper orientation (verify TOP marking and front orientation). Carefully place cylinder head on block, aligning dowel pins. Install NEW cylinder head bolts finger tight. Torque cylinder head bolts to 65 Nm (48 lb-ft) in proper sequence from center outward, then apply additional angle torque per Toyota specification (typically +90 degrees in multiple steps). Follow exact sequence and procedure from factory service manual.
    ⚠Do not use any sealant on head gasket. Head gasket has built-in sealing system.
    ⚠Cylinder head bolt torque sequence is critical. Improper sequence will cause head gasket failure.
    Torque spec

    Cylinder Head Bolts65 Nm (48 lb-ft)
16. 16

    Install camshafts
    Lubricate all camshaft journals and lobes with assembly lube. Position camshafts in cylinder head with timing marks in correct orientation for TDC cylinder #1. Install camshaft bearing caps in original positions with identification marks facing outward. Install camshaft bearing cap bolts finger tight. Torque camshaft bearing cap bolts to 14 Nm (10 lb-ft) in sequence from center outward in three progressive passes to prevent camshaft distortion. Verify camshafts rotate smoothly. Measure camshaft endplay with dial indicator (typical 0.05-0.20mm).
    ⚠Tighten camshaft bearing caps gradually in multiple passes. Sudden tightening can damage camshaft or journals.
    Torque spec

    Camshaft Bearing Cap Bolts14 Nm (10 lb-ft)
17. 17

    Install timing chain and components
    Verify crankshaft is at TDC cylinder #1 with keyway at 12 o'clock position. Install crankshaft timing sprocket. Install timing chain guides and torque bolts to 12 Nm. Install timing chain on crankshaft sprocket first, then route over camshaft sprockets while aligning timing marks per Toyota specification (paint marks from disassembly or factory marks). Install VVT-i actuators on camshaft ends while maintaining timing chain tension. Compress timing chain tensioner and install retaining pin/clip. Install tensioner and torque bolt to 25 Nm. Remove tensioner pin to apply tension. Rotate crankshaft two complete revolutions and verify timing marks realign correctly. Install new timing cover oil seal. Apply thin bead of RTV silicone to timing cover mating surface. Install timing cover with bolts torqued to 25 Nm in proper sequence. Install crankshaft pulley with NEW bolt torqued to 180 Nm (may require impact wrench and holding tool).
    ⚠️Incorrect timing chain installation will cause valve-to-piston contact and catastrophic engine damage. Verify timing marks multiple times.
    Torque spec

    Timing Chain Guide Bolts12 Nm (9 lb-ft)

    Timing Chain Tensioner Bolt25 Nm (18 lb-ft)

    Cover Bolts16 Nm (12 lb-ft)

    Crankshaft Pulley Bolt180 Nm (133 lb-ft)
18. 18

    Install valve cover and accessories
    Clean valve cover and cylinder head mating surfaces. Install new valve cover gasket or apply RTV per Toyota specification. Install valve cover and torque bolts to 10 Nm in sequence from center outward. Install ignition coils. Install intake manifold with new gasket and torque bolts to 25 Nm in proper sequence. Install exhaust manifold with new gasket, apply anti-seize to studs, and torque nuts to 30 Nm working from hot (center) to cold (outside). Install all sensors with NEW O-rings where applicable and torque sensor mounting bolts to 11 Nm. Install alternator, A/C compressor, and accessory brackets with mounting bolts torqued to 47 Nm. Install water pump with new gasket and thermostat.
    Torque spec

    Cover Bolts16 Nm (12 lb-ft)

    Intake Manifold Bolts25 Nm (18 lb-ft)

    Exhaust Manifold Nuts30 Nm (22 lb-ft)

    Mounting Bolts47 Nm (35 lb-ft)
19. 19

    Install flywheel (if removed)
    If flywheel was removed, clean flywheel and crankshaft mating surfaces thoroughly. Apply small amount of thread locker to NEW flywheel bolts. Install flywheel in correct orientation (alignment dowel pin). Install flywheel bolts and torque to 95 Nm (70 lb-ft) in star pattern. If flywheel bolts are TTY type, apply additional angle torque per specification.
    Torque spec

    Flywheel Bolts95 Nm (70 lb-ft)
20. 20

    Pre-installation preparation
    Install new oil drain plug with NEW crush washer torqued to 35 Nm. Install new oil filter. Fill engine with 5 quarts Toyota Genuine 0W-20 engine oil (do not overfill). Perform pre-oiling procedure if possible by rotating oil pump with drill motor to build oil pressure before starting. Double-check all bolts for proper torque. Verify no tools or rags are left in engine. Verify all electrical connections and vacuum lines are properly routed. Engine is now ready for installation back into vehicle.
    Torque spec

    Oil Drain Plug35 Nm (26 lb-ft)

Reassembly

1. After installation in vehicle, fill cooling system with 10 quarts Toyota Super Long Life Pink Coolant mixed per specifications
2. Perform proper bleeding procedure for cooling system to remove all air pockets
3. Reconnect battery and perform throttle body relearn procedure
4. Prime fuel system by cycling ignition on/off three times before cranking
5. Start engine and verify oil pressure builds immediately (within 5 seconds)
6. Monitor for any leaks at gasket surfaces during warm-up period
7. Allow engine to reach operating temperature and verify thermostat operation
8. Perform complete inspection for leaks after first heat cycle
9. Drive vehicle through gentle break-in period per Toyota recommendations (typically 500 miles with varying RPM, no sustained high load)
10. Perform first oil and filter change at 500 miles to remove break-in debris
11. Re-torque cylinder head bolts after first heat cycle if specified by Toyota procedure (most modern engines do not require this)

Verification

• Verify oil pressure gauge shows normal pressure (30+ psi at idle when warm)
• Listen for any abnormal engine noises including knocking, ticking, or rattling
• Verify no oil leaks from valve cover, oil pan, timing cover, or head gasket
• Verify no coolant leaks from water pump, thermostat housing, or head gasket
• Check for proper engine operation at idle and under load with no misfires or hesitation
• Verify engine reaches normal operating temperature (approximately 195°F) and cooling fan cycles properly
• Scan for diagnostic trouble codes and verify no codes present
• Perform compression test on all cylinders to verify consistent readings (within 10% variation)
• Perform leak-down test to verify ring seal and valve sealing if desired (typical 5-10% leakage acceptable)
• Monitor oil consumption over first 1000 miles to verify proper ring seating (minimal consumption expected after break-in)

More procedures for this vehicle