Engine Oil Cooler

This procedure covers removal and replacement of the engine oil cooler on the 2016-2021 Honda Civic 1.5L Turbo, including coolant drainage, component access, and proper torque specifications during reinstallation.

Warnings

Tools required

Parts

• Engine oil cooler assembly × 1 — 15400-5AA-A02 or equivalent
• Oil cooler O-rings and seals kit × 1 — Use OEM specification
• Coolant drain plug washer × 1 — 94109-14000
• Hose clamps (if damaged) × 2 — Use OEM specification

Fluids

• Honda Type 2 Coolant (Blue) — 2 qt

Preparation

1. Ensure engine is completely cold to the touch (wait minimum 2 hours after last operation)
2. Raise vehicle and secure on jack stands at manufacturer specified lift points
3. Remove engine under cover and splash shields for access
4. Disconnect negative battery terminal to prevent accidental fan activation
5. Position drain pan beneath radiator drain plug location

Procedure

1. 1

   Drain Engine Coolant
   Locate the radiator drain plug at the bottom of the radiator on the driver side. Remove the radiator cap slowly to release any residual pressure. Open the drain plug and allow coolant to drain completely into the drain pan. Remove and replace the drain plug washer before reinstallation.
   Torque spec

   Coolant Drain Plug15 Nm (11 lb-ft)
2. 2

   Access Oil Cooler Assembly
   From underneath the vehicle, locate the oil cooler assembly on the passenger side of the engine block, below the oil filter housing. Remove any interfering brackets or heat shields using 10mm socket. The oil cooler has two coolant hoses connected via spring clamps and is secured by mounting bolts to the engine block.
3. 3

   Disconnect Coolant Hoses
   Using hose clamp pliers, compress and slide the spring clamps away from the oil cooler connections on both inlet and outlet hoses. Have shop rags ready as residual coolant will drain. Twist hoses gently while pulling to separate from oil cooler fittings. Inspect hose ends for cracks or deterioration.
4. 4

   Remove Oil Cooler Mounting Bolts
   Using a 12mm socket, remove the two mounting bolts securing the oil cooler to the engine block. Support the oil cooler assembly while removing the final bolt to prevent it from dropping. Note the orientation and position of any alignment dowels or guides.
5. 5

   Remove Oil Cooler Assembly
   Carefully pull the oil cooler assembly away from the engine block. Residual oil and coolant may drain from the unit. Place the old oil cooler in a suitable container. Inspect the mounting surface on the engine block for damage, corrosion, or debris.
6. 6

   Clean Mounting Surfaces
   Thoroughly clean the oil cooler mounting surface on the engine block using brake cleaner and shop rags. Remove all traces of old gasket material, oil residue, and coolant deposits. Ensure the surface is completely dry and free of contaminants before proceeding.
7. 7

   Install New O-Rings and Seals
   Install new O-rings onto the replacement oil cooler assembly in the proper grooves. Lightly coat the O-rings with clean engine oil to aid installation and prevent pinching. Ensure O-rings are seated completely in their grooves without twisting or damage.
8. 8

   Install New Oil Cooler Assembly
   Align the new oil cooler with the mounting holes on the engine block, ensuring any alignment dowels engage properly. Push the assembly firmly into position, ensuring O-rings seat correctly. Hand-thread both mounting bolts before tightening.
9. 9

   Torque Oil Cooler Mounting Bolts
   Using a torque wrench and 12mm socket, tighten the oil cooler mounting bolts in a cross pattern to the specified torque value. Verify both bolts are torqued evenly and the assembly sits flush against the engine block without gaps.
   Torque spec

   Mounting Bolts26 Nm (19 lb-ft)
10. 10

    Reconnect Coolant Hoses
    Reconnect the inlet and outlet coolant hoses to the oil cooler assembly, ensuring they are fully seated onto the fittings. Push each hose on firmly until it bottoms out. Position the spring clamps over the hose connection points and release to secure. Verify clamps are positioned in the correct groove on each fitting.
11. 11

    Reinstall Access Components
    Reinstall any heat shields, brackets, or covers that were removed for access. Ensure all fasteners are tight and components are properly positioned. Reinstall the engine under cover and splash shields.
12. 12

    Refill Cooling System
    Using Honda Type 2 Blue coolant, refill the cooling system through the radiator cap opening. Fill slowly to allow air to escape. Refill to the MAX line on the coolant reservoir. Install the radiator cap securely. Reconnect the negative battery terminal.
13. 13

    Bleed Cooling System
    Start the engine and allow it to reach normal operating temperature with the heater set to maximum heat. Monitor coolant level in the reservoir and add as needed. Allow the engine to run until the cooling fans cycle on and off at least twice to ensure proper air purging from the system.
    ⚠Monitor for coolant leaks around oil cooler connections during warm-up. Shut down immediately if leaks are observed.

Reassembly

1. Double-check all coolant hose connections for proper seating and clamp positioning
2. Verify no tools or rags were left in the engine compartment
3. Top off coolant reservoir to MAX line after cooling system is fully bled
4. Inspect ground under vehicle for any coolant or oil leaks before returning to service

Verification

• Start engine and verify no coolant leaks from oil cooler assembly or hose connections
• Confirm cooling system maintains proper pressure and temperature during test drive
• Check engine oil and coolant for cross-contamination (milky appearance indicates ongoing issue)
• Verify coolant level remains stable after several heat cycles
• Monitor coolant reservoir level over the next few days for any drops indicating slow leaks

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