Heater Hoses

This procedure covers the removal and replacement of heater hoses on the 2016-2021 Honda Civic 1.5L Turbo engine, including coolant drainage, hose disconnection, and system refilling.

Warnings

Tools required

Parts

• Heater inlet hose × 1 — Use OEM specification
• Heater outlet hose × 1 — Use OEM specification
• Hose clamps (as needed) × 4 — Use OEM specification

Fluids

• Honda Type 2 Coolant (Blue) — 6 qt

Preparation

1. Ensure the engine is completely cold before beginning work
2. Park the vehicle on a level surface and engage the parking brake
3. Disconnect the negative battery terminal to prevent electrical issues
4. Remove the engine cover by pulling up on the front edge, then lifting off
5. Locate the radiator drain plug on the lower driver side of the radiator
6. Place a large drain pan under the radiator drain plug

Procedure

1. 1

   Drain the cooling system
   Remove the radiator cap slowly to release any residual pressure. Open the radiator drain plug using a 10mm socket and allow coolant to drain completely into the drain pan. Once drained, reinstall and tighten the drain plug.
   Torque spec

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

   Locate the heater hoses
   Identify the two heater hoses on the passenger side of the engine bay. The inlet hose connects from the engine block to the firewall, and the outlet hose returns from the firewall to the coolant pipe near the thermostat housing. Trace both hoses to confirm their routing.
3. 3

   Remove the air intake duct
   Loosen the clamp at the throttle body using a flathead screwdriver. Disconnect the air intake duct from the throttle body and remove it to gain better access to the heater hoses. Set the duct aside in a clean area.
   Torque spec

   Hose Clamps3 Nm (2 lb-ft)
4. 4

   Disconnect the heater inlet hose at the engine block
   Using hose clamp pliers or a flathead screwdriver, loosen the hose clamp securing the inlet hose to the engine block fitting. Twist the hose gently to break the seal, then pull it off the fitting. Be prepared for residual coolant spillage. Use shop towels to catch any remaining coolant.
5. 5

   Disconnect the heater outlet hose at the coolant pipe
   Locate the heater outlet hose connection at the coolant pipe assembly near the thermostat housing. Loosen the hose clamp and twist the hose to break the seal. Remove the hose from the fitting and allow any remaining coolant to drain into a shop towel.
   ⚠The coolant pipe connection point is plastic and can be damaged if excessive force is used. Twist gently and use penetrating oil if the hose is stuck.
6. 6

   Disconnect hoses at the firewall connections
   Working from inside the engine bay, access the firewall side of both heater hoses. Loosen the hose clamps at both firewall fittings. Twist each hose to break the seal and pull them off the fittings. Note the routing of the hoses for reinstallation.
7. 7

   Remove the old heater hoses
   Carefully route the old heater hoses out of the engine bay, noting any clips or brackets that secured them in place. Remove any mounting clips from the old hoses if they are reusable. Inspect the hose fittings on the engine block, coolant pipe, and firewall for damage or corrosion.
8. 8

   Prepare and install new heater inlet hose
   Install new hose clamps on the new heater inlet hose before installation. Route the new inlet hose from the firewall to the engine block, ensuring it follows the original path and does not contact hot or moving components. Connect the hose to the firewall fitting first, then to the engine block fitting. Do not fully tighten clamps yet.
9. 9

   Install new heater outlet hose
   Install new hose clamps on the outlet hose. Route the new outlet hose from the firewall to the coolant pipe near the thermostat housing. Ensure proper routing away from the turbocharger and exhaust components. Connect both ends but leave clamps loose for final positioning.
10. 10

    Secure all hose connections
    Verify that all four hose connections are fully seated on their fittings. Position each hose clamp over the raised bead on each fitting. Tighten all hose clamps in sequence: firewall inlet, engine block inlet, firewall outlet, coolant pipe outlet. Ensure hoses are not kinked or touching sharp edges.
    Torque spec

    Hose Clamps3 Nm (2 lb-ft)
11. 11

    Reinstall the air intake duct
    Reconnect the air intake duct to the throttle body. Ensure proper seating and tighten the clamp securely.
    Torque spec

    Hose Clamps3 Nm (2 lb-ft)
12. 12

    Refill the cooling system
    Using a funnel, add Honda Type 2 coolant (blue) to the radiator until it reaches the bottom of the filler neck. Fill the coolant reservoir to the MAX line. Install the radiator cap. Reconnect the negative battery terminal.
13. 13

    Bleed the cooling system
    Start the engine and allow it to idle with the heater set to maximum temperature. Run the engine until the cooling fans cycle on and off twice. Monitor the coolant level in the reservoir and add coolant as needed. Check for leaks at all hose connections while the engine is running.
    ⚠Do not remove the radiator cap while the engine is running or hot. Monitor coolant temperature and shut off the engine immediately if overheating occurs.

Reassembly

1. Reinstall the engine cover by aligning the rear clips first, then pressing down on the front until it clicks into place
2. Check the coolant level in the reservoir after the engine has cooled completely and top off to the MAX line if necessary
3. Dispose of used coolant properly at an approved recycling facility

Verification

• With the engine cold, verify the coolant level is at the MAX line on the reservoir
• Inspect all four hose connections for signs of coolant leaks with the engine cold
• Start the engine and allow it to reach operating temperature, then inspect all connections again for leaks
• Verify that the heater produces hot air when set to maximum temperature
• Check for proper cooling system operation by confirming the radiator fans cycle on at normal operating temperature
• After the first test drive, recheck coolant level and inspect all hose connections once more

Related trouble codes on this vehicle

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