Coolant Bypass Pipe

This procedure covers the removal and replacement of the coolant bypass pipe on the 2014-2018 Chevrolet Silverado 1500 with the 5.3L V8 L83 engine, which routes coolant between the water pump and engine block.

Warnings

Tools required

Parts

• Coolant bypass pipe assembly × 1 — GM 12674144 or equivalent
• Bypass pipe O-rings × 2 — Included with pipe or separate kit
• Hose clamps (if reusing old clamps) × 2 — Use OEM specification

Fluids

• ACDelco DEX-COOL (Orange) — 2 qt

Preparation

1. Ensure engine is completely cool to the touch
2. Park vehicle on level surface and engage parking brake
3. Disconnect negative battery cable to prevent electrical issues
4. Remove engine cover by pulling upward on retention clips
5. Place drain pan under radiator drain petcock

Procedure

1. 1

   Drain cooling system
   Open the radiator drain petcock at the bottom of the radiator on the driver side. Allow coolant to drain into pan. If equipped with engine block drain plugs, open them as well for more complete drainage. Capture and measure drained coolant for refill reference.
   Torque spec

   Drain Petcock8 Nm (6 lb-ft)
2. 2

   Remove engine cooling fan
   Using appropriate socket, remove the four fan shroud mounting bolts. Carefully lift the fan and shroud assembly straight up and out of the engine bay as a unit. Set aside in a safe location to provide better access to the bypass pipe area.
   Torque spec

   Fan Bolts14 Nm (10 lb-ft)
3. 3

   Locate and access bypass pipe
   The coolant bypass pipe runs from the water pump inlet to the engine block on the driver side front of the engine. Identify the pipe and trace both connection points. You may need to remove or reposition the alternator or other accessories for better access depending on specific vehicle configuration.
4. 4

   Disconnect hoses from bypass pipe
   Using hose clamp pliers, release the spring clamps or loosen screw-type clamps on any coolant hoses connected to the bypass pipe. Carefully twist and pull hoses off the pipe connections. Inspect hoses for cracks or deterioration and replace if necessary.
   ⚠Residual coolant will drain from hoses. Have rags ready to catch spillage.
   Torque spec

   Hose Clamps3 Nm (2 lb-ft)
5. 5

   Remove bypass pipe mounting hardware
   Locate and remove the bolts securing the bypass pipe to the engine block and water pump housing. The pipe typically has 2-3 mounting bolts. Note the bolt locations and any brackets or support clips attached to the pipe for proper reassembly.
   Torque spec

   Housing Bolts17 Nm (13 lb-ft)
6. 6

   Extract old bypass pipe
   Carefully work the bypass pipe out of its mounting position. The pipe has O-ring seals at the connection points which may stick. Gently twist and pull to break the seal. Use a small pry bar if necessary but avoid scratching sealing surfaces on the block or water pump housing.
   ⚠Do not use excessive force or pry against soft aluminum surfaces. Damage to sealing surfaces will cause coolant leaks.
7. 7

   Clean sealing surfaces
   Remove old O-rings from the block and water pump housing connection points. Use a wire brush and clean rag to thoroughly clean all sealing surfaces where the bypass pipe connects. Remove any old coolant residue, corrosion, or debris. Inspect surfaces for damage, deep scratches, or pitting that could prevent proper sealing.
8. 8

   Prepare new bypass pipe
   Install new O-rings onto the new bypass pipe at both connection points. Lightly lubricate the O-rings with fresh coolant to aid installation and prevent damage during insertion. Ensure O-rings are properly seated in their grooves and not twisted.
9. 9

   Install new bypass pipe
   Carefully align the new bypass pipe with the mounting holes in the engine block and water pump housing. Push the pipe into position, ensuring both O-ring connections seat properly. Install mounting bolts finger-tight initially to hold the pipe in position.
10. 10

    Torque bypass pipe mounting bolts
    Using a torque wrench, tighten the bypass pipe mounting bolts to specification. Tighten in a crossing pattern if multiple bolts are present to ensure even seating of the pipe connections.
    Torque spec

    Housing Bolts17 Nm (13 lb-ft)
11. 11

    Reconnect coolant hoses
    Slide coolant hoses back onto the bypass pipe connections. Ensure hoses are fully seated on their fittings. Install and position hose clamps 1/4 inch from the end of each hose. Tighten clamps to specification using appropriate tool.
    Torque spec

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

    Reinstall cooling fan assembly
    Lower the fan and shroud assembly back into position, ensuring it seats properly on its mounting points. Install and torque the four fan shroud mounting bolts to specification in a crossing pattern.
    Torque spec

    Fan Bolts14 Nm (10 lb-ft)
13. 13

    Refill cooling system
    Close radiator drain petcock and any block drain plugs removed earlier, torquing to specification. Locate the cooling system bleed screw on the thermostat housing or upper radiator hose area and open it. Fill the cooling system with ACDelco DEX-COOL coolant through the radiator or surge tank. Continue filling until coolant flows from the bleed screw without air bubbles, then close and torque the bleed screw.
    ℹ️Fill slowly to allow air to escape. System capacity is approximately 18 quarts but you may only need 2-3 quarts to replace what was drained.
    Torque spec

    Bleed Screw8 Nm (6 lb-ft)

    Drain Petcock8 Nm (6 lb-ft)
14. 14

    Burp cooling system and check for leaks
    Reconnect battery. Start engine and allow to warm up to operating temperature with heater on high. Monitor temperature gauge to ensure normal operation. Check all bypass pipe connections for leaks. Add coolant as needed to maintain proper level. Rev engine to 2500 RPM several times to help purge remaining air from the system.
    ⚠Monitor temperature gauge closely during first warm-up. If temperature rises abnormally, shut off engine immediately and check for leaks or air pockets.

Reassembly

1. Reinstall engine cover by pressing down on retention clips until they click into place
2. Recheck coolant level after engine has cooled and top off if necessary
3. Inspect ground under vehicle for any coolant drips after the first drive cycle

Verification

• Start engine and verify coolant circulates properly with no leaks at bypass pipe connections
• Confirm engine reaches normal operating temperature (approximately 195-220°F) without overheating
• Check that heater produces hot air indicating proper coolant flow through entire system
• Inspect all connections after a short test drive for any signs of coolant seepage
• Verify coolant level remains stable in surge tank after system has been cycled hot and cold

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