Remove and replace the engine oil cooler assembly on a 1966 Corvette 327 V8, including disconnecting oil lines, coolant lines, and mounting hardware.

Warnings

Tools required

Parts

• Engine oil cooler assembly × 1 — Use OEM specification
• Oil cooler mounting gasket × 1 — Use OEM specification
• Oil line copper crush washers × 4 — Use OEM specification
• Coolant hose clamps × 2 — Use OEM specification
• Thread sealant (non-hardening) × 1 — Permatex #2 or equivalent

Fluids

• 5W-30 Conventional engine oil — 1 qt
• DEX-COOL Extended Life coolant — 2 qt

Preparation

1. Ensure engine is completely cold (at least 2 hours after last operation).
2. Disconnect negative battery cable.
3. Raise vehicle on jack stands to safe working height with adequate clearance.
4. Place drain pan under oil cooler area to catch oil and coolant.
5. Remove engine oil dipstick to vent crankcase and facilitate draining.
6. Locate oil cooler assembly on driver side of engine block below exhaust manifold.

Procedure

1. 1

   Drain coolant from oil cooler circuit
   Loosen the lower radiator hose clamp at the radiator and drain approximately 2 quarts of coolant into drain pan. This reduces coolant loss when disconnecting oil cooler lines. Alternatively, if full coolant system service is due, drain the entire cooling system via the radiator petcock or lower radiator hose.
2. 2

   Disconnect coolant inlet line
   Locate the coolant inlet line connection at the oil cooler body. Loosen the hose clamp using a flathead screwdriver or socket. Twist the hose gently to break it free from the cooler fitting, then pull straight off. Be prepared for residual coolant to drain. Position drain pan to catch fluid.
3. 3

   Disconnect coolant outlet line
   Repeat the process for the coolant outlet line. Loosen the hose clamp and remove the hose from the oil cooler outlet fitting. Allow all residual coolant to drain into the pan. Inspect hoses for cracks or deterioration and replace if necessary during reassembly.
4. 4

   Disconnect oil supply line from block
   Using a line wrench (flare nut wrench) to prevent rounding, slowly loosen the oil supply line fitting at the engine block connection point. The fitting uses a 9/16" line wrench. Loosen approximately one full turn and pause to allow residual oil pressure to bleed off. Continue loosening until the line can be separated. Have a catch container ready as approximately 0.5 quarts of oil will drain from the line.
5. 5

   Disconnect oil return line from block
   Using the line wrench, loosen the oil return line fitting at the engine block. This line returns cooled oil to the engine and will also contain residual oil. Remove the fitting completely and position the line end into a drain pan. Allow oil to drain fully before proceeding.
6. 6

   Disconnect oil lines from cooler body
   Move to the oil cooler body and disconnect both the supply and return oil lines at their connection points to the cooler. Use the line wrench to prevent damage to the fittings. These connections typically use 1/2" or 9/16" fittings. Remove the copper crush washers and discard them; new washers must be installed during reassembly.
7. 7

   Remove oil cooler mounting bolts
   Locate the oil cooler mounting bolts securing the cooler assembly to the engine block adapter. Remove the 2 mounting bolts using an appropriate socket. These are typically 7/16" or 1/2" hex head bolts. Support the oil cooler with one hand while removing the final bolt to prevent it from falling.
8. 8

   Remove oil cooler assembly
   Carefully pull the oil cooler assembly straight away from the engine block mounting surface. The cooler may be stuck due to the gasket seal. Gently wiggle and pull to break the seal. Once free, lower the cooler assembly and remove it from the vehicle. Be cautious of any remaining oil or coolant dripping from the unit.
9. 9

   Clean mounting surfaces
   Using a wire brush and scraper, thoroughly clean the engine block mounting surface where the oil cooler attaches. Remove all old gasket material, ensuring the surface is completely clean and flat. Wipe the surface with a shop rag dampened with parts cleaner. Inspect the mounting surface for cracks or damage.
10. 10

    Prepare new oil cooler
    Inspect the new oil cooler assembly for shipping plugs or protective caps and remove them. Install the new mounting gasket onto the oil cooler body, ensuring proper alignment with all ports and bolt holes. Apply a thin film of clean engine oil to the gasket to aid installation and initial sealing.
11. 11

    Install new oil cooler assembly
    Position the new oil cooler assembly with gasket against the engine block mounting surface. Align the mounting bolt holes carefully. Start both mounting bolts by hand to ensure proper thread engagement and alignment. Thread bolts at least 3-4 turns by hand before using tools.
12. 12

    Torque oil cooler mounting bolts
    Tighten the oil cooler mounting bolts in an alternating pattern to ensure even gasket compression. Snug the bolts gradually, then torque to 18-22 ft-lbs in two stages: first to 10 ft-lbs, then to final torque. This prevents gasket distortion and ensures proper sealing.
13. 13

    Reconnect oil lines to cooler
    Install new copper crush washers on both oil line fittings. Connect the oil supply line to the oil cooler inlet port and the return line to the outlet port. Thread fittings by hand first to ensure proper engagement. Using the line wrench, tighten the fittings to snug plus 1/2 turn beyond finger tight. Do not overtighten as this can damage the copper washers or crack the cooler body.
14. 14

    Reconnect oil lines to engine block
    Install new copper crush washers on the engine block oil line fittings. Connect both the supply and return lines to their respective block ports. Thread by hand first, then tighten with a line wrench to snug plus 1/2 turn. Verify both connections are secure but not overtightened.
15. 15

    Reconnect coolant lines
    Slide new hose clamps onto the coolant hoses if replacing old clamps. Push the coolant inlet hose firmly onto the oil cooler inlet fitting until it bottoms against the bead. Position the clamp 1/4 inch from the hose end and tighten securely. Repeat for the coolant outlet hose. Ensure clamps are positioned past the fitting bead for proper retention.
16. 16

    Refill fluids
    Reinstall the oil dipstick. Add 1 quart of 10W-30 conventional engine oil to compensate for oil lost from the cooler and lines. Refill the cooling system with conventional ethylene glycol (green IAT) coolant mixed 50/50 with water to the proper level, adding approximately 2 quarts or the amount drained earlier. Do not overfill.

Reassembly

1. Reconnect negative battery cable.
2. Lower vehicle from jack stands.
3. Double-check all oil and coolant line connections for tightness.
4. Verify drain pans are removed from under vehicle.

Verification

• Start engine and allow it to idle. Monitor oil pressure gauge to ensure normal pressure is achieved within 10-15 seconds.
• With engine idling, carefully inspect all oil line connections at the cooler and block for leaks. Look for oil weeping or dripping.
• Inspect coolant hose connections at the oil cooler for leaks. Watch for coolant seepage or drips.
• Allow engine to reach normal operating temperature (thermostat open, approximately 180-195°F). Recheck all connections for leaks under operating temperature and pressure.
• Check engine oil level on dipstick and add oil if necessary to bring to proper full mark.
• Check coolant level in radiator when cool and top off if needed.
• Test drive vehicle for 10-15 minutes, then recheck all connections for leaks while engine is hot.
• After 24 hours of operation, recheck oil and coolant levels and inspect for any delayed leaks.

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