Radiator Hose - Upper

This procedure covers removal and replacement of the upper radiator hose on the 2016-2021 Honda Civic 1.5L Turbo engine, including coolant draining and refilling.

Warnings

Tools required

Parts

• Upper radiator hose × 1 — 19501-5AA-A01 (OEM) or equivalent
• Hose clamps (if corroded or damaged) × 2 — Use OEM specification

Fluids

• Honda Type 2 Coolant (Blue) — 2 qt

Preparation

1. Ensure engine is completely cold (at least 2 hours after last operation)
2. Park vehicle on level ground and engage parking brake
3. Open the hood and secure it in the upright position
4. Locate the upper radiator hose running from the engine thermostat housing to the radiator upper inlet

Procedure

1. 1

   Drain the cooling system
   Place a drain pan beneath the radiator. Remove the radiator cap slowly by turning it counterclockwise to release any residual pressure. Locate the radiator drain plug on the driver's side lower corner of the radiator and open it to drain coolant into the pan. Allow coolant to drain completely.
2. 2

   Remove engine cover if equipped
   If your Civic has a plastic engine cover, lift it up from the front edge and pull forward to release the mounting grommets. Set aside.
   Torque spec

   Cover Screws10 Nm (8 lb-ft)
3. 3

   Loosen the thermostat housing hose clamp
   Locate the hose clamp securing the upper radiator hose to the thermostat housing (engine side). Use a flathead screwdriver or hose clamp pliers to loosen the clamp. Slide the clamp back along the hose away from the connection point, at least 2-3 inches.
4. 4

   Loosen the radiator inlet hose clamp
   Locate the hose clamp at the radiator upper inlet (radiator side). Loosen this clamp using a flathead screwdriver or hose clamp pliers and slide it back along the hose away from the radiator connection.
5. 5

   Remove the upper radiator hose
   Twist the hose gently while pulling to break the seal at both the thermostat housing and radiator inlet connections. Remove the hose completely. Some residual coolant will drain out, so have towels ready. Inspect both connection points for debris or damage.
6. 6

   Prepare and install the new upper radiator hose
   Compare the new hose to the old one to verify correct fit. Clean the thermostat housing and radiator inlet connection surfaces with a shop towel. Position the hose clamps on the new hose before installation. Install the new hose onto the thermostat housing first, pushing it fully onto the connection until it seats against the stop ridge.
7. 7

   Connect hose to radiator inlet
   Route the hose to the radiator upper inlet, ensuring it follows the same path as the original and has no kinks or sharp bends. Push the hose fully onto the radiator inlet until it seats completely against the stop ridge.
8. 8

   Secure hose clamps
   Position the hose clamps approximately 1/2 inch from the ends of the hose at both connection points. Tighten the thermostat housing clamp first, then the radiator inlet clamp to the specified torque. Ensure clamps are positioned over the raised bead area of each connection.
   Torque spec

   Hose Clamps3 Nm (2 lb-ft)
9. 9

   Close radiator drain and refill coolant
   Close the radiator drain plug securely. Fill the cooling system with Honda Type 2 (blue) coolant through the radiator cap opening. Fill slowly to allow air to escape. Fill until coolant reaches the bottom of the radiator cap neck. Also check and fill the coolant reservoir to the MAX line.
10. 10

    Bleed air from cooling system
    With the radiator cap still off, start the engine and let it idle. Turn the heater to maximum temperature and fan speed. Allow the engine to warm up to operating temperature while monitoring coolant level. Add coolant as the level drops during the bleeding process. Continue until the thermostat opens and coolant circulates (you'll see flow in the radiator). Run until cooling fans cycle on, then turn off the engine.
11. 11

    Final coolant level adjustment
    Once the engine has cooled (at least 30 minutes), recheck the radiator coolant level and top off to the bottom of the filler neck if needed. Check the coolant reservoir level and adjust to the MAX line. Install the radiator cap securely by turning clockwise until it clicks.

Reassembly

1. Reinstall the engine cover if equipped, aligning the grommets and pressing down firmly until seated
2. Verify all tools and drain pans are removed from the engine bay
3. Wipe up any spilled coolant from engine components and painted surfaces

Verification

• Start the engine and visually inspect both hose connections for coolant leaks while the engine warms up
• Check that the upper radiator hose becomes hot to the touch as the engine reaches operating temperature, confirming coolant circulation
• Verify the cooling fans activate when the engine reaches normal operating temperature
• After the first drive cycle, recheck coolant level in both the radiator and reservoir when engine is cold and top off if necessary
• Monitor for leaks and proper engine temperature over the next few days of operation

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