Radiator Hose - Upper

Replace the upper radiator hose on a 1970 AMC Rebel Machine with 390ci V8 engine to prevent coolant leaks and overheating.

Warnings

Tools required

Parts

• Upper radiator hose × 1 — Use OEM specification or Gates 21461
• Hose clamps (2) × 2 — Worm gear style, 1.5-2 inch diameter

Fluids

• Engine coolant (50/50 mix) — 2 qt

Preparation

1. Ensure engine is completely cold to the touch (minimum 2 hours after last operation)
2. Park vehicle on level ground and engage parking brake
3. Place drain pan under radiator drain petcock on passenger side lower corner of radiator
4. Remove radiator cap slowly to relieve any residual pressure

Procedure

1. 1

   Drain coolant from radiator
   Open the radiator drain petcock located at the lower passenger side of the radiator by turning counterclockwise. Drain sufficient coolant to drop level below the upper radiator hose connection point (approximately 1-2 gallons). Close petcock when complete.
2. 2

   Loosen radiator-side hose clamp
   Locate the worm gear clamp securing the upper hose to the radiator inlet neck. Use a flathead screwdriver to loosen the clamp screw by turning counterclockwise. Slide the clamp back away from the radiator neck approximately 2-3 inches along the hose.
3. 3

   Loosen thermostat housing hose clamp
   Locate the worm gear clamp at the thermostat housing on the front of the engine block (driver side). Loosen the clamp screw and slide it back along the hose away from the housing connection.
4. 4

   Remove upper radiator hose
   Twist the hose back and forth while pulling to break the seal at both connection points. Remove the hose from the radiator inlet neck first, then from the thermostat housing. Residual coolant will drain; have shop rags ready. Remove old clamps from the hose if they are to be reused.
5. 5

   Clean connection surfaces
   Inspect the radiator inlet neck and thermostat housing connection points for corrosion, scale buildup, or damage. Use a wire brush or shop rag to clean both connection surfaces thoroughly. Check for any cracks or damage that would prevent a proper seal.
6. 6

   Install new hose clamps
   Slide new worm gear clamps onto the new upper radiator hose before installation. Position one clamp approximately 3-4 inches from each end of the hose.
7. 7

   Install new upper radiator hose
   Push the hose firmly onto the thermostat housing first, ensuring it seats completely against the housing shoulder. Then connect the opposite end to the radiator inlet neck, pushing until fully seated. The hose should fit snugly without excessive force.
8. 8

   Position and tighten hose clamps
   Slide both clamps to position them approximately 1/2 inch back from the end of each connection point. Tighten the radiator-side clamp firmly with a flathead screwdriver until snug but not over-tightened (the hose should compress slightly but not bulge). Repeat for the thermostat housing clamp.
9. 9

   Refill cooling system
   Pour a 50/50 mixture of coolant and water into the radiator through the filler neck until full. Start with approximately 2 quarts, then add as needed. Allow coolant to settle for a few minutes and top off as necessary.
10. 10

    Bleed air from cooling system
    With the radiator cap still off, start the engine and allow it to warm up to normal operating temperature. Watch the coolant level in the radiator and add more as the thermostat opens and air purges from the system. Squeeze the upper radiator hose gently to help release air pockets.
    ⚠Keep hands and tools clear of the fan and belts while engine is running.

Reassembly

1. Once the thermostat has opened and no more air bubbles appear, top off the radiator to the filler neck and install the radiator cap
2. Allow engine to return to idle and check for leaks at both hose connections
3. Wipe down any spilled coolant from engine and radiator surfaces

Verification

• With engine at operating temperature, visually inspect both hose connections for coolant leaks
• Check that the upper radiator hose is firm and hot to the touch, indicating proper coolant flow
• Verify coolant level is correct after engine cools down completely
• Monitor coolant level and temperature gauge during the first few drives to ensure system is sealed and functioning properly

More procedures for this vehicle