This procedure covers removal and replacement of the coolant outlet housing (thermostat housing) on a 1966 Chevrolet Corvette 327 V8, including gasket replacement and coolant refill.

Warnings

Tools required

Parts

• Coolant outlet housing gasket × 1 — Use OEM specification
• Coolant outlet housing (if damaged or corroded) × 1 — Use OEM specification

Fluids

• DEX-COOL Extended Life (Orange) — 2 qt

Preparation

1. Ensure the engine is completely cold to the touch
2. Park the vehicle on level ground and engage the parking brake
3. Place drain pan under the radiator drain petcock
4. Remove the radiator cap slowly to release any residual pressure

Procedure

1. 1

   Drain coolant from the system
   Open the radiator drain petcock located at the bottom passenger side of the radiator. Drain approximately 2-3 quarts of coolant into the drain pan, enough to lower the coolant level below the outlet housing. Close the petcock once the level drops below the intake manifold.
2. 2

   Disconnect upper radiator hose
   Loosen the hose clamp securing the upper radiator hose to the coolant outlet housing. Use a flathead screwdriver for worm-drive clamps. Twist the hose gently to break the seal, then pull it off the outlet housing neck. Have a shop rag ready to catch residual coolant.
3. 3

   Disconnect coolant temperature sender wire
   Locate the coolant temperature sender threaded into the coolant outlet housing. Disconnect the single-wire electrical connector from the sender by pulling it straight off. Note the routing of the wire for reinstallation.
4. 4

   Remove coolant outlet housing bolts
   Remove the 2 bolts securing the coolant outlet housing to the intake manifold using a 9/16" socket. The bolts are located at the front and rear of the housing. Keep the bolts organized for reinstallation.
5. 5

   Remove coolant outlet housing and thermostat
   Lift the coolant outlet housing straight up off the intake manifold. The thermostat will be visible in the intake manifold opening beneath the housing. Remove the thermostat and note its orientation (spring side faces down into the engine). Inspect the housing for cracks, corrosion, or damage.
6. 6

   Clean gasket mating surfaces
   Use a gasket scraper or razor blade to carefully remove all old gasket material from both the intake manifold surface and the coolant outlet housing. Clean both surfaces thoroughly with a wire brush and shop rags. Ensure no debris falls into the intake manifold coolant passage.
7. 7

   Inspect and reinstall thermostat
   Inspect the thermostat for damage or corrosion. If replacing the coolant outlet housing, transfer the thermostat and temperature sender to the new housing. Place the thermostat into the intake manifold recess with the spring side facing down into the engine block.
8. 8

   Install new gasket and position housing
   Place the new coolant outlet housing gasket onto the intake manifold surface, aligning it with the bolt holes and coolant passage. Position the coolant outlet housing over the gasket, ensuring the thermostat stays seated properly and the gasket does not shift.
9. 9

   Install and torque housing bolts
   Thread both coolant outlet housing bolts by hand to ensure proper alignment. Tighten the bolts in an alternating pattern (front bolt first, then rear bolt, alternating back and forth) using a torque wrench to the specified torque.
   Torque spec

   Coolant Outlet/Housing Bolts12 Nm (9 lb-ft)
10. 10

    Reinstall coolant temperature sender
    If the sender was removed, apply a small amount of thread sealant to the sender threads and thread it into the coolant outlet housing. Torque the sender to specification using a wrench.
    Torque spec

    Coolant Temperature Sensor20 Nm (15 lb-ft)
11. 11

    Reconnect upper radiator hose
    Slide the upper radiator hose fully onto the coolant outlet housing neck. Position the hose clamp approximately 1/2 inch back from the end of the neck and tighten to specification. For spring clamps, ensure the clamp is properly seated in the groove.
    Torque spec

    Hose Clamps3 Nm (2 lb-ft)
12. 12

    Reconnect temperature sender wire
    Reconnect the single-wire electrical connector to the coolant temperature sender. Ensure the connection is secure and the wire is routed away from hot exhaust components and moving parts.
13. 13

    Refill cooling system
    Using a funnel, slowly pour conventional ethylene glycol coolant (green, IAT-type, 50/50 pre-mixed or properly mixed concentrate) into the radiator until it reaches the bottom of the filler neck. Install the radiator cap. Start the engine and allow it to reach operating temperature with the heater on high. Monitor coolant level and add as needed as air purges from the system.
14. 14

    Bleed air and verify level
    With the engine at operating temperature, carefully remove the radiator cap and add coolant to bring the level to the bottom of the filler neck. Reinstall the cap. Allow the engine to cool, then recheck the coolant level when cold and top off if necessary.

Reassembly

1. Ensure all hose clamps are properly tightened and positioned
2. Verify the temperature sender electrical connection is secure
3. Double-check for any tools or rags left in the engine compartment

Verification

• Start the engine and visually inspect the coolant outlet housing for leaks while the engine warms up
• Verify the temperature gauge responds normally as the engine reaches operating temperature
• Check the coolant level after the first drive cycle and top off if necessary
• Inspect under the vehicle for any coolant drips after a test drive

More procedures for this vehicle