Replace the front crankshaft seal on the 390ci V8 engine by removing the radiator, harmonic balancer, and timing cover to access and replace the front main seal.

Warnings

Tools required

Parts

• Front crankshaft seal × 1 — Use OEM specification for AMC 390ci V8
• Timing cover gasket × 1 — Use OEM specification for AMC 390ci V8
• Timing cover seal (oil pan to timing cover) × 1 — Use OEM specification
• Harmonic balancer bolt × 1 — Recommended replacement
• RTV silicone gasket maker × 1 — High-temp rated
• Engine assembly lubricant × 1 — For seal installation

Fluids

• Engine coolant (ethylene glycol) — 4 qt

Preparation

1. Ensure engine is completely cool
2. Disconnect negative battery cable
3. Drain cooling system by opening radiator petcock and removing lower radiator hose
4. Remove hood for better access (optional but recommended)
5. Support vehicle on jack stands if additional clearance needed for underbody access

Procedure

1. 1

   Remove radiator and cooling components
   Remove upper and lower radiator hoses from the radiator. Disconnect transmission cooler lines if equipped (automatic transmission). Remove radiator mounting bolts and carefully lift radiator from engine bay. Remove fan shroud if equipped. Remove fan blades and clutch assembly from water pump using appropriate wrench to hold pulley.
2. 2

   Remove drive belts and accessories
   Remove all drive belts from the front of the engine. Remove the alternator bracket bolts and position alternator aside without disconnecting wiring. Remove power steering pump mounting bolts if equipped and position pump aside without disconnecting hoses. Remove air conditioning compressor mounting bolts if equipped and secure compressor without disconnecting refrigerant lines.
3. 3

   Remove water pump
   Remove all water pump mounting bolts (typically 6-8 bolts around perimeter). Carefully remove water pump from timing cover. If pump is stuck, gently tap with rubber mallet to break gasket seal. Clean gasket surfaces on timing cover.
4. 4

   Remove crankshaft pulley and harmonic balancer
   Remove the crankshaft pulley bolts (if equipped with separate pulley). Mark the position of the harmonic balancer relative to the crankshaft snout with chalk or paint for reinstallation reference. Remove the center harmonic balancer bolt using a breaker bar (bolt is right-hand thread). Install harmonic balancer puller and carefully extract balancer from crankshaft. Do not hammer or pry on the balancer.
5. 5

   Remove timing cover bolts and oil pan bolts
   Remove all timing cover bolts, noting their locations as they may be different lengths. Remove the front oil pan bolts (typically 4-6 bolts) that secure the timing cover to the oil pan. Leave the remaining oil pan bolts in place.
6. 6

   Remove timing cover
   Carefully pry the timing cover away from the engine block using a pry bar at designated pry points. Work around the perimeter evenly to avoid cracking the cover. Once loose, pull timing cover forward off the crankshaft snout. The front seal will come out with the timing cover.
7. 7

   Remove old front seal from timing cover
   Using a seal puller or carefully positioned pry bar, extract the old front seal from the timing cover bore. Work around the seal perimeter to avoid damaging the timing cover seal bore. Clean the seal bore thoroughly with a clean rag and inspect for any damage, burrs, or scoring.
8. 8

   Prepare and install new front seal
   Apply a thin coat of engine assembly lubricant to the outer diameter of the new seal and the seal bore in the timing cover. Apply assembly lubricant to the seal lip (inner diameter). Position the seal with the lip facing toward the engine (spring side toward engine). Using a seal driver tool or appropriately sized large socket, drive the seal squarely into the bore until it seats flush with the timing cover surface.
9. 9

   Prepare timing cover for installation
   Clean all gasket surfaces on the timing cover and engine block using a gasket scraper and wire brush. Ensure all old gasket material and RTV are completely removed. Clean the crankshaft snout thoroughly and inspect for grooves or damage where the seal rides. Apply a thin bead of RTV silicone to the timing cover where it meets the oil pan rail. Install new timing cover gasket onto the timing cover or engine block per gasket manufacturer instructions.
10. 10

    Install timing cover
    Carefully slide the timing cover over the crankshaft snout, ensuring the front seal lip is not damaged during installation. Align the timing cover with dowel pins on the engine block. Install all timing cover bolts finger-tight, then torque in a crisscross pattern from center outward to manufacturer specification (typically 12-15 ft-lbs for AMC V8, verify for your application). Install and torque the front oil pan bolts.
11. 11

    Install harmonic balancer
    Clean the crankshaft snout and harmonic balancer bore with a clean rag. Apply a thin coat of engine assembly lubricant to the crankshaft snout and seal contact area. Align the harmonic balancer with the marks made during removal and slide onto the crankshaft by hand. Install the harmonic balancer bolt and washer. Torque the balancer bolt to manufacturer specification (typically 90-100 ft-lbs for AMC 390ci, verify for your application). Some applications require additional rotation specification.
12. 12

    Reinstall water pump and accessories
    Install water pump with new gasket, torquing bolts in a crisscross pattern to manufacturer specification (typically 10-13 ft-lbs). Reinstall power steering pump, air conditioning compressor, and alternator to their mounting brackets. Install all drive belts and adjust to proper tension per manufacturer specifications.
13. 13

    Reinstall cooling system components
    Reinstall fan clutch and fan blades to water pump. Install fan shroud if equipped. Reinstall radiator into engine bay and secure with mounting bolts. Connect transmission cooler lines if equipped. Install upper and lower radiator hoses and secure with clamps.
14. 14

    Refill cooling system and check for leaks
    Close radiator petcock. Fill cooling system with appropriate coolant mixture (typically 50/50 ethylene glycol and water). Reconnect negative battery cable. Start engine and bring to operating temperature while monitoring for leaks around the timing cover, water pump, and all hose connections. Check coolant level and top off as necessary after engine reaches operating temperature and thermostat opens.

Reassembly

1. Ensure all cooling system connections are properly tightened and leak-free
2. Verify drive belt tensions are correct after initial run
3. Recheck coolant level after first few heat cycles
4. Monitor for oil leaks from timing cover area during first 100 miles of operation

Verification

• Start engine and verify no oil leaks from front seal or timing cover gasket
• Confirm no coolant leaks from water pump or radiator connections
• Verify proper engine operating temperature and thermostat operation
• Check for unusual vibrations that could indicate improper harmonic balancer installation
• After 500 miles, recheck timing cover bolts and harmonic balancer bolt torque

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