engine

Long Block Replacement

for 2021 Honda Accord 1.5L I4 Turbo · FWD

Editorial review:Chris Hackleman — Master Technician · 20+ years · Jeff Moore — Master Lexus & Toyota Mechanic · 20+ years

Difficulty

Expert

Time

12.0 h

Tools

Steps

✓Expert-verified. Personally reviewed and approved by OLP's master technicians (Chris Hackleman & Jeff Moore — 20+ years each). Always follow the vehicle's factory service information and torque specs.

Complete replacement of the long block assembly on a 2018-2024 Honda Accord 1.5L turbo engine, including removal of cylinder head, block, and internal components, and installation of new long block.

Warnings

⚠️Ensure engine is completely cool before beginning work. Hot coolant and engine components can cause severe burns.

⚠️Relieve fuel system pressure before disconnecting fuel lines. Fuel spray can cause fire or injury.

⚠Use proper engine lifting equipment rated for at least 500 lbs. Improper support can result in serious injury or death.

⚠Never work under an engine supported only by a hoist. Use jack stands and blocks as secondary support.

⚠All cylinder head bolts, main bearing cap bolts, connecting rod bolts, and flywheel bolts are torque-to-yield (TTY) and must be replaced with new hardware.

ℹ️Mark all electrical connectors, vacuum lines, and hoses during disassembly to ensure correct reinstallation.

ℹ️This procedure assumes the long block comes as a complete assembly. Transfer external components from old engine to new long block as needed.

Tools required

Engine hoist with load levelerEssential

Engine support bar or fixtureEssential

Torque wrench (10-100 Nm range)Essential

Torque angle gaugeEssential

Coolant drain pan (minimum 8 quart capacity)Essential

Oil drain panEssential

Transmission jackEssential

Socket set (metric 8mm-19mm)Essential

Wrench set (metric)Essential

Pry bar set

Fuel line disconnect tool setEssential

Coolant system pressure tester

Honda timing alignment toolsEssential

Plastic scraper for gasket removalEssential

Shop vacuum

Parts

Long block assembly (1.5L turbo) × 1 — Use OEM Honda part
Cylinder head gasket × 1 — Use OEM specification
Valve cover gasket × 1 — Use OEM specification
Intake manifold gasket × 1 — Use OEM specification
Exhaust manifold gasket × 1 — Use OEM specification
Timing cover gasket × 1 — Use OEM specification
Oil pan gasket × 1 — Use OEM specification
Oil drain plug crush washer × 1 — 94109-14000
Engine coolant (blue) × 1 — Honda Type 2 Blue
Engine oil 0W-20 × 1 — Honda Genuine 0W-20
Oil filter × 1 — Use OEM specification
Thermostat O-ring × 1 — Use OEM specification
Water pump O-rings (if applicable) × 1 — Use OEM specification
Spark plugs × 4 — NGK DILKAR8A8 or equivalent
Drive belt × 1 — Use OEM specification

Fluids

Honda Genuine 0W-20 — 4 qt
Honda Type 2 Coolant (Blue) — 6 qt

Preparation

Position vehicle on level surface and engage parking brake
Disconnect negative battery terminal and wait 3 minutes for airbag system capacitor discharge
Remove engine cover and upper decorative covers
Drain engine coolant completely from radiator drain and block drain plugs into appropriate container
Drain engine oil and remove oil filter
Relieve fuel system pressure by removing fuel pump fuse and running engine until it stalls
Raise and support vehicle on jack stands at all four corners
Remove front wheels and splash shields
Remove air intake system from air box to turbocharger inlet
Disconnect and cap all fuel lines using proper disconnect tools
Label and disconnect all electrical connectors on engine including injectors, coils, sensors, and alternator
Remove radiator, cooling fans, and all coolant hoses
Remove intercooler and charge air piping
Disconnect exhaust system at turbocharger flange
Remove drive belt and accessories (alternator, A/C compressor) - support A/C compressor without disconnecting lines
Support transmission with transmission jack from underneath
Attach engine hoist with proper lifting chain to designated lift points on engine

Procedure

1
Remove engine mount assemblies
Remove the upper engine mount bolts first, then the side mount through-bolts. Leave lower mounts attached until ready to lift. For right side mount, remove the mount bracket completely. For left side mount, remove upper bolt and loosen lower. Remove rear mount bolt from transmission side.
Torque spec
Mounting Bolts26 Nm (19 lb-ft)
2
Separate transmission from engine
Remove all transmission-to-engine mounting bolts. There are typically 4-5 bolts securing the bellhousing. Support transmission weight with transmission jack. Carefully separate transmission from engine by pulling straight back to avoid damaging input shaft or clutch components. Lower transmission enough to provide clearance.
⚠Ensure transmission is properly supported before removing final bolts. Transmission weighs approximately 100 lbs.
Torque spec
Transmission-to-Engine Bolts55 Nm (41 lb-ft)
3
Remove remaining engine connections
Disconnect any remaining vacuum lines, breather hoses, and ground straps. Remove throttle body connection and MAP sensor if not already done. Disconnect turbocharger oil feed line and oil return line. Verify all connections are clear before lifting engine.
ℹ️Take photos during disassembly for reference during reassembly, particularly of vacuum line routing and electrical connector positions.
4
Lift and remove engine assembly
Double-check all connections are disconnected. Remove remaining engine mount bolts. Using engine hoist, slowly lift engine while guiding it away from transmission. Tilt engine as needed using load leveler to clear firewall and chassis components. Lift engine completely out of engine bay and position on engine stand or suitable work surface.
⚠️Have an assistant guide the engine during removal. Watch for snagged hoses, wires, or contact with body panels.
5
Transfer external components to new long block
Remove and transfer the following components from old engine to new long block: turbocharger assembly, exhaust manifold, intake manifold, fuel rail and injectors, ignition coils, throttle body, thermostat housing, sensors (coolant temp, oil pressure, knock, cam/crank position), oil cooler assembly, starter motor, engine mounts and brackets, and any other external components. Inspect all components for wear and replace as needed.
⚠Apply anti-seize compound to exhaust manifold stud threads before installing nuts. Work from center outward in hot-to-cold pattern.
Torque spec
Exhaust Manifold Nuts30 Nm (22 lb-ft)
Intake Manifold Bolts25 Nm (18 lb-ft)
Sensor Bolts10 Nm (8 lb-ft)
6
Install valve cover and timing components
Install new valve cover gasket and valve cover, tightening bolts in sequence from center outward. Install timing chain components if not already installed on long block, ensuring proper alignment marks. Install timing cover with new gasket, tightening 8mm bolts in proper sequence. Install timing chain tensioner with pin compressed, then release pin after installation.
⚠Verify timing marks are correctly aligned before installing timing cover. Incorrect timing will cause severe engine damage.
Torque spec
Cover Bolts15 Nm (11 lb-ft)
Timing Chain Tensioner Bolt25 Nm (18 lb-ft)
7
Install oil pan and drain plug
Clean all gasket surfaces on oil pan and block thoroughly. Install new oil pan gasket and position oil pan. Install oil pan bolts in crisscross pattern, torquing in multiple passes to specification. Install oil drain plug with new crush washer.
ℹ️Over-tightening oil pan bolts can warp the pan or crack the sealing surface. Use torque wrench and multiple passes.
Torque spec
Oil Pan Bolts12 Nm (9 lb-ft)
Oil Drain Plug35 Nm (26 lb-ft)
8
Install flywheel and clutch assembly
If removed, install flywheel with new bolts to crankshaft flange. Tighten in star pattern to specification. Install clutch disc and pressure plate assembly, centering clutch disc with alignment tool. Torque pressure plate bolts gradually in star pattern.
⚠Use only new flywheel bolts as these are torque-to-yield. Reusing old bolts can result in bolt failure and catastrophic engine damage.
Torque spec
Flywheel Bolts95 Nm (70 lb-ft)
9
Install engine into vehicle
Attach hoist to new long block assembly at lift points. Carefully lower engine into engine bay, tilting as necessary to clear firewall and chassis. Align engine with transmission while lowering. Once positioned, guide engine onto engine mounts and align transmission bellhousing.
⚠️Work slowly and have assistant guide engine. Ensure no wiring harnesses or hoses are pinched during installation.
10
Mate engine to transmission
With transmission supported on transmission jack, carefully push engine and transmission together. Ensure proper alignment of input shaft with clutch disc. Do not force - if components don't mate easily, check alignment. Install all transmission-to-engine bolts and torque to specification in star pattern.
⚠Never use transmission bolts to pull engine and transmission together. Components must align freely or damage will occur.
Torque spec
Transmission-to-Engine Bolts55 Nm (41 lb-ft)
11
Install engine mounts
Install all engine mount bolts, starting with lower mounts, then side mounts, then upper mounts. Torque all mounting bolts to specification. Ensure engine is properly positioned and not placing stress on any mount before final tightening.
Torque spec
Mounting Bolts26 Nm (19 lb-ft)
12
Reconnect all systems
Reconnect all electrical connectors, ensuring proper seating and locking tabs engaged. Reconnect all vacuum lines and breather hoses per photos/labels. Connect fuel lines with new O-rings. Reconnect turbocharger oil feed and return lines with new crush washers. Install new drive belt. Reinstall alternator and A/C compressor with proper belt routing. Reconnect exhaust at turbo flange with new gasket. Reinstall intercooler and charge air piping.
ℹ️Verify all electrical connectors are fully seated. Loose connections can cause driveability issues or sensor faults.
13
Reinstall cooling system components
Reinstall all coolant hoses with new clamps as needed. Install radiator and cooling fans. Connect all coolant hoses to proper locations. Fill cooling system with Honda Type 2 coolant (blue) to proper level. Bleed cooling system by running engine with radiator cap off until thermostat opens and air is purged.
⚠Use only Honda Type 2 (blue) coolant. Other coolant types can cause corrosion and cooling system damage in aluminum engines.
14
Fill fluids and perform initial start
Install new oil filter. Fill engine with 4.0 quarts of Honda Genuine 0W-20 oil. Install new spark plugs if not already done. Reinstall air intake system. Reconnect battery negative terminal. Turn ignition to ON position without starting to prime fuel system (repeat 3 times). Check for fuel leaks. Start engine and immediately check for oil pressure, unusual noises, and leaks. Allow engine to idle and warm to operating temperature.
⚠️Monitor engine closely during first start. Immediately shut down if unusual noises, smoke, or leaks are observed.

Reassembly

Reinstall splash shields and front wheels
Lower vehicle from jack stands
Reinstall engine cover and decorative covers
Check and top off all fluid levels after engine has cooled
Verify drive belt tension and routing is correct
Check for any coolant, oil, or fuel leaks around all connection points

Verification

Start engine and verify stable idle with no unusual noises or vibrations
Check that all warning lights extinguish after startup (check engine, oil pressure)
Verify no coolant, oil, or fuel leaks at all connection points and gaskets
Test drive vehicle to verify proper engine operation under load
Monitor engine temperature to confirm proper cooling system operation
Check for diagnostic trouble codes using OBD-II scanner
Verify turbocharger boost operation under acceleration
Recheck oil level after test drive and top off if necessary
Inspect all mounting bolts and connections after 50-100 miles of operation
Monitor for any leaks or issues during first 500 miles of operation