Water Pump

This procedure covers removal and replacement of the water pump on a 1970 AMC Rebel Machine with 390ci V8 engine, including cooling system drain, accessory removal, and refill.

Warnings

Tools required

Parts

• Water pump assembly × 1 — Use OEM specification for AMC 390
• Water pump gasket × 1 — Use OEM specification
• Fan belt (if worn or damaged) × 1 — Check belt condition during removal
• Coolant (ethylene glycol) × 1 — Approximately 4-5 gallons 50/50 mix
• Heater hose (lower if deteriorated) × 1 — Inspect during procedure

Fluids

• Ethylene glycol coolant (50/50 mix with distilled water) — 20 qt

Preparation

1. Park vehicle on level surface and apply parking brake
2. Allow engine to cool completely for at least 2 hours
3. Disconnect negative battery cable
4. Place drain pan under radiator drain petcock
5. Remove radiator cap slowly to relieve any residual pressure
6. Open radiator drain petcock and drain coolant completely
7. Remove drain pan and position under water pump area

Procedure

1. 1

   Remove fan shroud
   Remove the bolts securing the fan shroud to the radiator support. Leave shroud resting on fan blades. This provides clearance for fan removal without damaging radiator.
2. 2

   Remove fan and fan clutch assembly
   Using a fan clutch wrench or large adjustable wrench, turn the fan clutch nut counterclockwise (reverse thread on most AMC applications with serpentine-style fans, but verify your configuration). Remove the four bolts securing the fan clutch to the water pump hub if equipped with standard threads. Remove fan, clutch, and shroud as an assembly.
3. 3

   Remove drive belts
   Loosen alternator adjustment bolt and pivot bolt, push alternator toward engine block to release belt tension. Remove alternator belt. If equipped with power steering or air conditioning, loosen adjustment bolts on those accessories and remove their respective belts. Note belt routing for reinstallation.
4. 4

   Remove water pump pulley
   Remove the bolts securing the water pump pulley to the water pump hub. If pulley spins, use a pulley holder tool or have an assistant hold the pulley with a strap wrench. Remove pulley and set aside.
5. 5

   Disconnect hoses from water pump
   Loosen hose clamps on the lower radiator hose where it connects to the water pump inlet. Twist hose gently to break seal and remove from pump. Disconnect heater hose from water pump if equipped. Allow remaining coolant to drain into pan.
6. 6

   Remove water pump mounting bolts
   Remove all water pump mounting bolts securing pump to timing chain cover. There are typically 5-6 bolts of varying lengths on the AMC 390. Note bolt locations as different length bolts go in specific positions. The pump may be stuck to the timing cover with old gasket material.
7. 7

   Remove water pump from engine
   Carefully pry water pump away from timing chain cover using a scraper or pry bar at the casting flanges (never pry against machined sealing surfaces). Remove pump from engine. If pump is stuck, tap gently with a soft mallet around the perimeter.
8. 8

   Clean mounting surface
   Thoroughly clean all old gasket material from the timing chain cover mounting surface using a gasket scraper. Be careful not to gouge or scratch the sealing surface. Use a wire brush to clean bolt holes and remove any corrosion. Wipe surface clean with a lint-free cloth.
9. 9

   Prepare new water pump
   Compare new water pump to old unit to verify correct replacement. Check that new pump hub rotates freely. Apply a thin bead of RTV silicone to one side of the new water pump gasket, then position gasket on the water pump flange. Allow RTV to tack up for 5 minutes.
10. 10

    Install new water pump
    Apply a thin bead of RTV silicone to the timing cover side of the gasket. Position water pump assembly against timing chain cover, aligning bolt holes. Start all mounting bolts by hand to ensure proper alignment. Tighten bolts in a criss-cross pattern to approximately 13-15 ft-lbs (torque specification not verified in database, use manufacturer specification). Allow RTV to cure per manufacturer instructions before refilling coolant.
11. 11

    Reconnect hoses
    Reconnect lower radiator hose to water pump inlet. Position hose clamp over the beaded section of the pump inlet and tighten securely. Reconnect heater hose if removed. Ensure all hose clamps are positioned properly and tightened.
12. 12

    Install water pump pulley
    Position water pump pulley on hub and install mounting bolts finger-tight. Do not fully tighten yet as the pulley will spin when installing drive belts.
13. 13

    Install drive belts and adjust tension
    Route drive belts according to original configuration. Position alternator belt first, then adjust alternator position to achieve proper belt tension (approximately 1/2 inch deflection with moderate thumb pressure at belt center). Tighten alternator adjustment and pivot bolts. Repeat for power steering and air conditioning belts if equipped. Now tighten water pump pulley bolts securely.
14. 14

    Install fan clutch and fan assembly
    Position fan shroud over fan blades. Install fan clutch and blade assembly onto water pump hub. Tighten fan clutch nut or bolts according to thread direction (reverse or standard thread). Secure fan shroud to radiator support with original bolts.
15. 15

    Refill cooling system
    Close radiator drain petcock. Fill radiator with 50/50 mixture of ethylene glycol coolant and distilled water. Fill until coolant reaches bottom of radiator neck. Start engine and allow to warm up to operating temperature with radiator cap off. Add coolant as level drops due to air purging. Once engine reaches operating temperature and thermostat opens, top off coolant and install radiator cap.

Reassembly

1. Verify all hose clamps are properly positioned and tightened
2. Check drive belt tension and adjust if necessary after initial run-in period
3. Ensure fan clutch and blade assembly is secure and does not contact shroud or radiator
4. Reconnect negative battery cable

Verification

• Start engine and check for coolant leaks around water pump gasket and hose connections
• Verify coolant circulation by observing flow in radiator when thermostat opens
• Check engine temperature gauge for normal operating temperature
• Listen for abnormal noises from water pump bearing (grinding or squealing indicates failure)
• Verify fan clutch engages properly as engine warms up
• Check coolant level after test drive and top off if necessary
• Re-check belt tension after 50-100 miles of operation

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