Replace the coolant bypass pipe on the 1.5L turbocharged engine, which routes coolant between the engine block, turbocharger, and cylinder head.

Warnings

Tools required

Parts

• Coolant bypass pipe assembly × 1 — 19505-5AA-A01 or equivalent OEM
• Coolant bypass pipe O-rings × 3 — Usually included with pipe assembly
• Hose clamps (if reusing old clamps are damaged) × 2 — Spring-type or worm-gear clamps

Fluids

• Honda Type 2 Coolant (Blue) — 3 qt

Preparation

1. Ensure the engine is completely cold to the touch (wait minimum 2 hours after last operation)
2. Park vehicle on level ground and engage parking brake
3. Remove engine cover by pulling upward on the front edge, then lifting off
4. Place coolant drain pan under the radiator drain petcock on the driver's side of the radiator
5. Open the radiator cap slowly to release any residual pressure
6. Locate the coolant drain petcock at the bottom of the radiator and open to drain coolant into the pan

Procedure

1. 1

   Drain remaining coolant from engine block
   After the radiator has drained, locate the coolant drain plug on the engine block (driver's side, below the exhaust manifold). Remove the drain plug using a 12mm socket and allow all coolant to drain completely. Reinstall the drain plug hand-tight for now.
2. 2

   Remove air intake components
   Disconnect the intake air temperature sensor connector on the intake tube. Loosen the hose clamp at the throttle body and turbocharger inlet using pliers. Remove the intake tube by pulling it off both connections. Set aside to provide access to the coolant bypass pipe area.
3. 3

   Access the coolant bypass pipe
   The coolant bypass pipe is located on the firewall side of the engine, connecting to the cylinder head, engine block, and turbocharger coolant supply. Use a flashlight to identify the pipe routing and connections. Note the orientation of hose clamps and connection points for reassembly.
4. 4

   Disconnect coolant hoses from bypass pipe
   Using pliers, carefully squeeze and slide the spring-type hose clamps away from the connections on the bypass pipe. There are typically 2-3 rubber hose connections. Twist the hoses gently to break them free from the pipe, then pull them off. Have shop towels ready to catch residual coolant.
5. 5

   Remove bypass pipe mounting bolts
   Locate the mounting bolts securing the bypass pipe to the cylinder head and engine block (typically two 10mm bolts). Use a socket with extension to access these bolts from above or below as needed. Remove both bolts completely and retain them if they are in good condition.
6. 6

   Extract the old coolant bypass pipe
   Carefully wiggle and pull the bypass pipe assembly from its mounting points. The pipe has multiple O-ring connections that may be stuck due to heat cycling. Do not pry against aluminum components. If stuck, gently twist while pulling to break the O-ring seal. Inspect the removed pipe for cracks or corrosion.
7. 7

   Clean mounting surfaces and inspect O-ring grooves
   Using a shop towel or wire brush, clean all coolant residue from the mounting surfaces on the cylinder head and engine block. Inspect the O-ring grooves for damage, corrosion, or debris. Clean thoroughly to ensure proper seal with new O-rings. Check that threads in mounting holes are clean and undamaged.
8. 8

   Install new O-rings on replacement bypass pipe
   Lubricate the new O-rings lightly with clean coolant (never use petroleum-based lubricants). Install the O-rings into the grooves on the new bypass pipe assembly. Ensure each O-ring is seated properly in its groove and not twisted. Typically there are 3 O-rings on this pipe assembly.
9. 9

   Install new coolant bypass pipe
   Carefully align the new bypass pipe with the mounting points on the cylinder head and engine block. Push the pipe firmly into place, ensuring all O-ring connections seat fully. The pipe should sit flush against the mounting surfaces. Install the mounting bolts finger-tight initially, then torque to specification using the torque wrench.
   Torque spec

   Housing Bolts13 Nm (10 lb-ft)
10. 10

    Reconnect coolant hoses
    Slide the coolant hoses back onto their respective connections on the bypass pipe. Ensure each hose is pushed fully onto the pipe until it bottoms out. Reposition the hose clamps over the hose-to-pipe connection area and secure them. If installing new worm-gear clamps, torque to specification.
    Torque spec

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

    Reinstall air intake components
    Reinstall the intake tube by connecting it to the throttle body and turbocharger inlet. Ensure both ends are fully seated. Tighten the hose clamps securely. Reconnect the intake air temperature sensor connector until it clicks into place.
12. 12

    Close drain points and refill cooling system
    Torque the coolant drain plug in the engine block to specification. Close and torque the radiator drain petcock. Locate the coolant bleed screw on top of the thermostat housing and open it 1-2 turns. Slowly fill the radiator with Honda Type 2 coolant through the radiator cap opening until coolant flows from the bleed screw without air bubbles, then close the bleed screw to specification. Continue filling to the radiator neck. Fill the coolant reservoir to the MAX line.
    Torque spec

    Coolant Drain Plug15 Nm (11 lb-ft)

    Drain Petcock6 Nm (5 lb-ft)

    Bleed Screw6 Nm (5 lb-ft)
13. 13

    Bleed air from cooling system
    With the radiator cap still off, start the engine and let it idle. Set the heater to maximum temperature and fan speed. As the engine warms, watch the coolant level in the radiator and add coolant as needed. The coolant level will drop as air is purged and the thermostat opens. Run until the cooling fans cycle on, then turn off the engine.
    ⚠Monitor engine temperature closely during bleeding. If temperature rises above normal, shut off the engine immediately and allow it to cool.
14. 14

    Final fill and cap installation
    After the engine cools for 10-15 minutes, recheck the radiator coolant level and top off to the neck if needed. Install the radiator cap securely. Check the coolant reservoir level and ensure it is between MIN and MAX marks. Reinstall the engine cover.

Reassembly

1. Double-check that all hose clamps are secure and properly positioned over connections
2. Verify the coolant reservoir is filled to the MAX line with Honda Type 2 coolant
3. Ensure the radiator cap is properly seated and locked in place
4. Confirm the engine cover is reinstalled and properly seated on all mounting points

Verification

• Start the engine and visually inspect all connections on the coolant bypass pipe for leaks while the engine is cold
• Allow the engine to reach operating temperature and verify no leaks appear at the bypass pipe connections
• Confirm the heater produces hot air at idle and that engine temperature remains stable in normal range
• After the first drive cycle (50-100 miles), recheck coolant level in both the radiator and reservoir when cold, and top off if necessary
• Inspect the area around the bypass pipe for coolant stains or drips during the first week of operation

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