This procedure covers the removal and replacement of both the upper and lower radiator hoses on a 1966 Chevrolet Corvette with the 327ci V8 engine, including coolant draining and refilling.

Warnings

Tools required

Parts

• Upper radiator hose × 1 — Use OEM specification or Gates 21472
• Lower radiator hose × 1 — Use OEM specification or Gates 21471
• Hose clamps (worm-gear style) × 4 — 1.5-2 inch diameter
• Coolant DEX-COOL Extended Life × 1 — Use OEM specification

Fluids

• DEX-COOL Extended Life (Orange) — 10 qt

Preparation

1. Ensure the engine is completely cold to the touch
2. Park the vehicle on level ground and engage the parking brake
3. Place protective fender covers over the fenders to prevent damage during work
4. Gather all tools, parts, and fluids before beginning
5. Have adequate lighting available in the engine bay

Procedure

1. 1

   Drain the cooling system
   Position a drain pan beneath the radiator. Locate the petcock drain valve at the lower corner of the radiator (verify side on your specific radiator). Open the petcock by turning it counterclockwise. Once coolant begins flowing, carefully remove the radiator cap to allow faster drainage and venting. Allow the system to drain completely, which should yield approximately 8-10 quarts of coolant from the radiator petcock (full system capacity is roughly 16-17 quarts; the block retains coolant unless separately drained).
2. 2

   Access and inspect the upper radiator hose
   Locate the upper radiator hose connecting the top of the radiator to the thermostat housing on the intake manifold. Inspect the hose routing and note the orientation of any bends. Check the condition of the existing hose clamps; 1966 Corvettes typically used spring clamps or worm-gear clamps depending on service history.
3. 3

   Remove the upper radiator hose clamps
   Using hose clamp pliers or standard pliers, squeeze and slide the spring clamps (if equipped) away from the connection points, or use a flathead screwdriver to loosen worm-gear clamps by turning counterclockwise. Position one clamp at least 3 inches back from each end of the hose (radiator neck and thermostat housing).
4. 4

   Remove the upper radiator hose
   Twist the hose back and forth while pulling to break the seal at both the radiator neck and thermostat housing. If the hose is stuck due to age, carefully use a utility knife to make a single lengthwise cut in the hose end to facilitate removal—take care not to score the radiator neck or housing. Remove the hose completely and set aside the old clamps if reusing.
5. 5

   Remove the lower radiator hose clamps
   Locate the lower radiator hose connecting the bottom of the radiator to the water pump inlet on the passenger side of the engine. Using the same technique as the upper hose, release or loosen the clamps at both the radiator outlet and water pump inlet. Slide the clamps back along the hose.
6. 6

   Remove the lower radiator hose
   Twist and pull the lower hose from both connection points. The lower hose may have accumulated more sediment and be more difficult to remove. If stuck, use the utility knife method as before. Once removed, allow any remaining coolant to drain from the hose and connections into the drain pan.
7. 7

   Clean the connection surfaces
   Using a wire brush and shop rags, thoroughly clean the radiator neck and outlet, thermostat housing neck, and water pump inlet. Remove all old rubber residue, corrosion, and debris. Inspect each fitting for cracks, excessive corrosion, or damage. The surfaces should be smooth and clean for proper sealing with new hoses.
8. 8

   Install the new lower radiator hose
   Slide two new worm-gear hose clamps onto the new lower radiator hose before installation. Position the hose with the correct orientation (the hose has a specific shape to clear engine components). Push the hose firmly onto the radiator outlet until it bottoms out against the bead, then push the other end onto the water pump inlet until fully seated. Position one clamp over each connection point approximately 0.5 inches from the end of the hose, and tighten each clamp securely with a flathead screwdriver until snug—do not overtighten, which can damage the hose.
9. 9

   Install the new upper radiator hose
   Slide two new worm-gear hose clamps onto the new upper radiator hose. Route the hose from the radiator neck to the thermostat housing, ensuring proper clearance from the fan blades, fan shroud, and other accessories. Push both ends fully onto their respective necks until seated against the beads. Position the clamps approximately 0.5 inches from each hose end and tighten securely with a flathead screwdriver.
10. 10

    Close the radiator drain and refill the system
    Close the radiator petcock by turning it clockwise until snug—do not overtighten. Remove the drain pan from beneath the vehicle. Using a funnel, slowly pour a 50/50 mix of conventional green ethylene glycol coolant and distilled water into the radiator fill neck until the level reaches the bottom of the neck. Pour slowly to allow air to escape and prevent air pockets from forming.
11. 11

    Burp the cooling system
    With the radiator cap still off, start the engine and allow it to idle. Watch the coolant level in the radiator—it will drop as the thermostat opens and coolant circulates through the engine. Continue adding coolant as needed to maintain the level at the bottom of the fill neck. Run the engine until the upper radiator hose becomes hot to the touch, indicating the thermostat has opened and coolant is circulating. Squeeze the upper radiator hose several times to help release trapped air bubbles.
12. 12

    Complete the fill and install the radiator cap
    Once the thermostat has opened and no more air bubbles are rising in the radiator, top off the coolant to the bottom of the fill neck one final time. Install the radiator cap by aligning the tabs and turning clockwise until it locks into place. Allow the engine to continue running and reach full operating temperature while monitoring for leaks at all hose connections.
13. 13

    Inspect for leaks and verify operation
    With the engine at operating temperature, visually inspect all four hose clamp connections for signs of coolant seepage. Check the area beneath the vehicle for drips. Verify that the mechanical (belt-driven) fan and water pump are turning properly and that the temperature gauge reads in the normal range. Rev the engine to 2000 RPM briefly and recheck all connections under increased cooling system pressure.

Reassembly

1. After the initial test run, allow the engine to cool completely and recheck the coolant level in the radiator—top off if necessary
2. Check coolant level again after the first 50 miles of driving and top off as needed as any remaining trapped air works its way out of the system
3. Inspect hose clamps after the first drive cycle and re-tighten if any have loosened due to thermal cycling

Verification

• No coolant leaks visible at any of the four hose clamp connections with the engine at operating temperature
• Engine reaches and maintains normal operating temperature without overheating
• Upper radiator hose becomes hot within 5-10 minutes of engine operation, indicating proper coolant flow
• Coolant level remains stable in the radiator after multiple heat cycles
• No coolant odor in the engine bay or visible steam from connections

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