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

Warnings

Tools required

Parts

• Upper radiator hose × 1 — Use OEM specification or Gates 21404
• Hose clamps (2) × 2 — 1.5-2 inch worm gear clamps

Fluids

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

Preparation

1. Ensure the engine is completely cold to the touch
2. Position the vehicle on level ground
3. Place drain pan under the radiator drain petcock on the passenger side lower corner of the radiator
4. Have replacement hose and clamps ready for installation

Procedure

1. 1

   Drain the cooling system
   Open the radiator drain petcock located at the bottom passenger side of the radiator by turning it counterclockwise. Allow approximately 5 quarts of coolant to drain into the pan. You do not need to drain the entire system, just enough to drop the coolant level below the upper hose connection point. Close the petcock when the coolant level is below the thermostat housing.
2. 2

   Remove the radiator cap
   Remove the radiator cap completely to break any vacuum and allow better draining. Set it aside in a clean location.
3. 3

   Loosen the thermostat housing clamp
   Locate the hose clamp securing the upper radiator hose to the thermostat housing on the front of the intake manifold. Using a flathead screwdriver or hose clamp pliers, loosen the worm gear clamp by turning counterclockwise. Slide the clamp back along the hose away from the thermostat housing neck, at least 2 inches back.
4. 4

   Loosen the radiator inlet clamp
   Locate the hose clamp at the radiator upper inlet neck. Loosen this clamp in the same manner and slide it back along the hose toward the center of the hose run.
5. 5

   Remove the upper radiator hose from thermostat housing
   Grip the hose near the thermostat housing and twist it back and forth while pulling to break it free from the housing neck. The hose may be stuck due to age and heat cycling. If necessary, carefully insert a flathead screwdriver between the hose and neck to break the seal, being careful not to gouge the metal housing. Work the hose off the neck completely.
6. 6

   Remove the hose from radiator inlet
   Repeat the twisting and pulling process at the radiator inlet. Remove the hose completely from the vehicle. Allow any remaining coolant in the hose to drain into the pan.
7. 7

   Clean the connection surfaces
   Use a wire brush or shop rag to clean any old rubber residue, corrosion, or debris from both the thermostat housing neck and the radiator inlet neck. Both surfaces should be smooth and clean to ensure a proper seal with the new hose.
8. 8

   Inspect the connection points
   Examine both the thermostat housing neck and radiator inlet neck for deep pitting, cracks, or damage. Minor surface corrosion is normal, but significant damage may require component replacement. Verify the thermostat housing is secure to the intake manifold with no leaks visible.
9. 9

   Install new clamps on the new hose
   Slide both new hose clamps onto the new upper radiator hose before installation. Position one clamp approximately 4 inches from each end of the hose. Orient the clamp screws so they will be easily accessible once installed.
10. 10

    Install hose onto thermostat housing
    Push the end of the new upper radiator hose firmly onto the thermostat housing neck. The hose should slide on approximately 2 inches and sit flush against the bead on the neck. Ensure the hose is fully seated with no gaps visible between the hose and the neck.
11. 11

    Install hose onto radiator inlet
    Route the hose to the radiator upper inlet and push it firmly onto the inlet neck. Ensure the hose follows a smooth path without kinks or sharp bends. The hose should be fully seated on the radiator neck bead as well.
12. 12

    Position and tighten the clamps
    Slide the clamp at the thermostat housing forward so it sits approximately 0.5 inches from the end of the housing neck, centered over the hose-to-neck connection. Tighten the clamp firmly with a screwdriver until the hose compresses slightly but is not crushed. Repeat for the radiator inlet clamp. Both clamps should be snug enough that the hose cannot be twisted by hand.
13. 13

    Refill the cooling system
    Using a funnel, pour fresh conventional ethylene glycol (green) coolant, mixed 50/50 with distilled water, into the radiator filler neck. Fill slowly to allow air to escape. Fill until coolant reaches the bottom of the filler neck. Squeeze the upper radiator hose several times to help purge air bubbles. Add more coolant as needed to maintain level.
14. 14

    Install radiator cap and burp the system
    Install the radiator cap securely. Start the engine and allow it to warm up to normal operating temperature with the heater on high. Monitor the temperature gauge to ensure it stays in the normal range. As the thermostat opens, the upper radiator hose should become hot to the touch. Run the engine for 10 minutes, then shut it off and allow it to cool for 30 minutes.
15. 15

    Check coolant level and inspect for leaks
    Once cooled, carefully remove the radiator cap and check the coolant level. Top off as necessary. Inspect both hose clamp connections for any signs of seepage or leakage. Check the ground under the vehicle for drips. Reinstall the radiator cap.

Reassembly

1. No disassembly beyond hose removal was required for this procedure

Verification

• Start the engine and bring it to full operating temperature while monitoring for leaks at both hose connections
• Verify the temperature gauge reads in the normal range and the upper hose becomes uniformly hot
• After a complete heat cycle and cooldown, recheck coolant level and inspect connections again for any seepage
• Test drive the vehicle and recheck coolant level when cold

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