Complete radiator replacement procedure for 2016-2021 Honda Civic 1.5L Turbo, including coolant system drain, radiator removal, and refill with bleeding.

Warnings

Tools required

Parts

• Radiator assembly × 1 — 19010-5AA-A51 (OEM reference)
• Lower radiator hose O-ring × 1 — Use OEM specification
• Upper radiator hose O-ring × 1 — Use OEM specification
• Radiator drain plug seal × 1 — Use OEM specification

Fluids

• Honda Type 2 Coolant (Blue) — 6 qt

Preparation

1. Ensure engine is completely cold (minimum 2 hours after last operation)
2. Park vehicle on level surface and apply parking brake
3. Disconnect negative battery cable to prevent cooling fan activation during work
4. Remove engine cover by pulling upward on front edge then sliding forward
5. Remove front undertray (five 10mm bolts and plastic clips)
6. Position drain pan under radiator drain plug location on passenger side lower corner

Procedure

1. 1

   Drain cooling system
   Slowly turn radiator cap counterclockwise to first detent to release any residual pressure, wait 10 seconds, then remove completely. Locate drain petcock on passenger side lower corner of radiator. Turn counterclockwise to open and drain coolant into pan. Once drained, remove and inspect drain plug seal for damage.
   Torque spec

   Drain Petcock5 Nm (4 lb-ft)
2. 2

   Remove upper radiator hose
   Use hose clamp pliers to compress and slide spring clamp back on upper radiator hose at radiator connection. Twist hose gently while pulling to break seal, then remove from radiator neck. Allow any remaining coolant to drain into pan placed underneath.
   Torque spec

   Upper/Lower Hose Clamps3 Nm (2 lb-ft)
3. 3

   Disconnect lower radiator hose
   Access lower radiator hose connection at bottom of radiator. Compress spring clamp with hose clamp pliers and slide back on hose. Twist and pull hose from radiator fitting. Ensure drain pan catches residual coolant.
   Torque spec

   Upper/Lower Hose Clamps3 Nm (2 lb-ft)
4. 4

   Disconnect transmission cooler lines (if equipped)
   For automatic transmission models, locate two transmission cooler lines connected to passenger side of radiator. Using flare nut wrench, loosen fittings at radiator (25 Nm specification for reinstallation). Cap or plug open lines immediately to prevent ATF contamination. Place shop towels underneath to catch ATF drips.
   ⚠Use only flare nut wrench on transmission cooler line fittings. Standard wrenches will round off fitting hex and require line replacement.
   Torque spec

   Transmission Cooler Lines25 Nm (18 lb-ft)
5. 5

   Disconnect cooling fan connectors
   Locate electrical connectors on both cooling fans (driver side condenser fan and passenger side radiator fan). Press release tabs and disconnect both connectors. Tuck wiring harness away from radiator removal path.
6. 6

   Remove upper radiator brackets
   Remove two upper radiator mounting brackets (one on each side). Each bracket is secured with one 12mm bolt (12 Nm torque specification). Support radiator by hand while removing second bracket to prevent tipping.
   ℹ️Upper brackets are plastic. Store in clean area and inspect for cracks before reinstallation.
   Torque spec

   Radiator Mount Bolts12 Nm (9 lb-ft)
7. 7

   Remove condenser mounting bolts
   Remove two 10mm bolts securing AC condenser to radiator (located at top corners). Carefully separate condenser from radiator without disconnecting AC lines. Support condenser and secure it forward toward hood latch area using mechanic's wire or zip ties to prevent AC line stress.
8. 8

   Remove radiator assembly
   Lift radiator assembly straight upward from engine bay. Radiator locates on lower rubber mounts with no bolts. Tilt top toward engine slightly while lifting to clear condenser and fan shroud. Keep radiator level to prevent residual coolant spillage. Inspect lower rubber mounting cushions and replace if deteriorated.
9. 9

   Transfer cooling fans to new radiator
   Remove cooling fan assemblies from old radiator if reusing fans. Each fan is secured with three 10mm bolts. Transfer fans to new radiator and torque bolts to 12 Nm. Ensure fan shroud clips engage properly with radiator tabs.
   Torque spec

   Radiator Mount Bolts12 Nm (9 lb-ft)
10. 10

    Install new radiator
    Position new radiator assembly above mounting locations. Ensure lower rubber mounts are in place. Guide radiator down onto lower mounts while clearing AC condenser and any chassis obstructions. Verify radiator is fully seated on both lower mounting cushions before proceeding.
11. 11

    Install upper mounting brackets and condenser
    Install upper radiator brackets on both sides and torque 12mm bolts to 12 Nm. Do not exceed torque specification as brackets are plastic. Reposition AC condenser against radiator and install two 10mm bolts at top corners.
    ⚠Over-torquing plastic radiator brackets will cause immediate or delayed cracking. Use torque wrench and do not exceed 12 Nm.
    Torque spec

    Radiator Mount Bolts12 Nm (9 lb-ft)
12. 12

    Reconnect hoses and lines
    Install new O-rings on radiator hose connections if provided with radiator. Connect lower radiator hose and position spring clamp within groove on radiator neck. Connect upper radiator hose and secure spring clamp in groove. For automatic transmission models, connect transmission cooler lines and torque to 25 Nm using flare nut wrench.
    Torque spec

    Upper/Lower Hose Clamps3 Nm (2 lb-ft)

    Transmission Cooler Lines25 Nm (18 lb-ft)
13. 13

    Reconnect electrical and install drain plug
    Reconnect both cooling fan electrical connectors ensuring positive lock engagement. Install new drain plug seal on drain petcock and install into radiator drain hole. Tighten hand-tight only to prevent cracking plastic threads (5 Nm maximum).
    Torque spec

    Drain Petcock5 Nm (4 lb-ft)
14. 14

    Refill cooling system
    Pour Honda Type 2 (blue) coolant directly into radiator neck until coolant reaches bottom of filler neck. Squeeze upper radiator hose several times to help purge air bubbles. Add more coolant as level drops. Install radiator cap. Fill coolant reservoir to MAX line with same coolant.
    ⚠Use only Honda Type 2 coolant. Turbo models require specific coolant formulation for turbocharger cooling circuit protection.
15. 15

    Bleed cooling system
    Reconnect negative battery cable. Start engine and set heater to maximum temperature and fan speed. Allow engine to reach operating temperature (cooling fans should cycle on and off twice). Monitor coolant level in radiator and reservoir, adding as needed. Rev engine to 3000 RPM three times to purge remaining air. Shut off engine and allow to cool, then recheck coolant level when cold and top off if necessary.

Reassembly

1. Reinstall front undertray with 10mm bolts and plastic clips
2. Reinstall engine cover by sliding rear tabs into slots then pressing front edge down until clips engage
3. Verify all cooling system connections are secure with no visible leaks
4. Check transmission fluid level if cooler lines were disconnected (automatic transmission models only)

Verification

• Start engine and verify both cooling fans operate when engine reaches operating temperature
• Check all hose connections and radiator fittings for coolant leaks while engine is at operating temperature
• Verify heater produces hot air at maximum temperature setting
• Confirm coolant reservoir level is at MAX line when engine is cold
• Monitor for coolant loss over next 100 miles and top off if needed as air pockets continue to purge
• For automatic transmission models, verify no ATF leaks at cooler line connections and check ATF level after test drive

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