Replace the coolant bypass pipe, which circulates coolant between the engine block and cylinder head. This procedure requires partial coolant drain and removal of several components for access.

Warnings

Tools required

Parts

• Coolant bypass pipe assembly × 1 — 16261-0H040
• O-rings for bypass pipe × 2 — Included with pipe assembly or separate
• Hose clamps (if corroded) × 2 — Use OEM specification

Fluids

• Toyota Super Long Life Coolant (Pink) — 2 qt

Preparation

1. Ensure engine is completely cold to the touch
2. Park vehicle on level surface and engage parking brake
3. Place drain pan under radiator drain plug
4. Remove engine splash shield if equipped (four 10mm bolts)
5. Locate coolant bypass pipe on rear of engine block below intake manifold

Procedure

1. 1

   Drain coolant system
   Open the radiator drain plug at the bottom of the radiator using a 10mm wrench or hand-tight if it is the petcock style. Drain approximately 2 quarts of coolant into drain pan. You do not need to drain the entire system, just enough to drop the level below the bypass pipe.
   Torque spec

   Coolant Drain Plug15 Nm (11 lb-ft)

   Drain Petcock6 Nm (5 lb-ft)
2. 2

   Remove engine cover
   Pull upward on the plastic engine cover to disengage the retaining clips. Set aside. This provides better access to the upper intake area.
3. 3

   Disconnect air intake tube
   Loosen the hose clamp at the throttle body using pliers or flathead screwdriver. Disconnect the air intake tube from the throttle body and move aside. Disconnect any electrical connectors or breather hoses attached to the intake tube.
4. 4

   Access bypass pipe area
   From above the engine, locate the coolant bypass pipe on the rear of the engine block. It connects the block to the cylinder head with two coolant hoses attached. You may need to remove the engine oil dipstick tube for better access (one 10mm bolt).
5. 5

   Disconnect coolant hoses from bypass pipe
   Using pliers, compress and slide the spring-style hose clamps away from the bypass pipe connections. If equipped with screw-type clamps, loosen them completely. Twist the hoses gently to break them free, then pull off the bypass pipe. Have shop towels ready to catch residual coolant.
   ⚠Residual coolant will spill when hoses are disconnected. Keep drain pan and towels ready.
   Torque spec

   Hose Clamps3 Nm (2 lb-ft)
6. 6

   Remove bypass pipe mounting bolts
   Remove the two 12mm bolts securing the bypass pipe to the engine block and cylinder head. The lower bolt may be difficult to access and may require a universal joint or extension. Support the pipe as you remove the second bolt.
   Torque spec

   Housing Bolts13 Nm (10 lb-ft)
7. 7

   Extract old bypass pipe
   Carefully wiggle and pull the bypass pipe assembly from the engine. The pipe has O-rings on both ends that seal against the block and head. You may need to rotate and manipulate the pipe to clear surrounding components. Inspect the O-ring grooves in the engine for damage or debris.
8. 8

   Clean mating surfaces
   Use a wire brush or shop towel to clean the O-ring sealing surfaces on the engine block and cylinder head where the bypass pipe mounts. Remove any old coolant residue, corrosion, or debris. Inspect for cracks or damage.
9. 9

   Prepare new bypass pipe
   Install new O-rings on both ends of the new bypass pipe if not pre-installed. Lightly coat the O-rings with clean coolant to aid installation and prevent tearing. Verify the pipe is the correct part by comparing to the old unit.
10. 10

    Install new bypass pipe
    Carefully align the new bypass pipe with the mounting holes in the engine block and cylinder head. Press the pipe firmly into place, ensuring both O-rings seat properly. The pipe should sit flush against both mounting surfaces. Start both mounting bolts by hand before tightening.
    ⚠Do not force the pipe. If it does not seat easily, remove and check O-ring alignment.
    Torque spec

    Housing Bolts13 Nm (10 lb-ft)
11. 11

    Reconnect coolant hoses
    Slide the coolant hoses onto the bypass pipe fittings. Ensure each hose is pushed fully onto the fitting until it bottoms out. Reposition the hose clamps over the hose-to-pipe connection point and secure them.
    Torque spec

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

    Reinstall removed components
    Reinstall the oil dipstick tube if removed (10mm bolt). Reconnect the air intake tube to the throttle body and tighten the hose clamp. Reconnect any electrical connectors or breather hoses. Reinstall the engine cover by pressing down on the clip locations until seated.
13. 13

    Close drain and refill coolant
    Close the radiator drain plug or petcock and tighten to specification. Open the cooling system bleed screw located on the thermostat housing or water inlet. Slowly pour fresh Toyota Super Long Life Coolant (Pink) into the radiator or coolant reservoir until coolant flows from the bleed screw without bubbles. Close the bleed screw.
    ℹ️Fill slowly to prevent air pockets. The bleed screw must be open during filling.
    Torque spec

    Bleed Screw6 Nm (5 lb-ft)

    Coolant Drain Plug15 Nm (11 lb-ft)

    Drain Petcock6 Nm (5 lb-ft)
14. 14

    Burp cooling system
    Fill the coolant reservoir to the FULL line. Start the engine and allow it to reach operating temperature with the heater on maximum. Watch the temperature gauge to ensure it stays in normal range. Add coolant as needed to maintain proper level. Monitor for leaks around the bypass pipe connections.
15. 15

    Final checks and reinstall splash shield
    After engine reaches operating temperature and cooling fan cycles, shut off engine and allow to cool. Recheck coolant level when cold and top off if needed. Inspect all connections at the bypass pipe for leaks. Reinstall engine splash shield if removed.

Reassembly

1. Torque all fasteners to specification using a calibrated torque wrench
2. Ensure all hose clamps are properly positioned over the hose-to-pipe connection
3. Double-check that the bleed screw is closed after bleeding procedure
4. Verify coolant reservoir is filled to FULL line when engine is cold

Verification

• Start engine and verify no coolant leaks around bypass pipe connections after reaching operating temperature
• Confirm engine temperature gauge reads in normal range during operation
• Check that heater produces hot air, indicating proper coolant circulation
• Verify coolant level remains stable after several heat cycles
• Inspect area under vehicle for any coolant drips or puddles

More procedures for this vehicle