Thermostat

Replace the thermostat on a 1992 Dodge Viper 8.0L V10, including coolant drain, housing removal, and system refill.

Warnings

Tools required

Parts

• Thermostat × 1 — Use OEM specification - 195°F opening temperature
• Thermostat housing gasket × 1 — Use OEM specification
• Engine coolant × 1 — Ethylene glycol 50/50 premix

Fluids

• coolant — 3 qt

Preparation

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

Procedure

1. 1

   Drain cooling system
   Open the radiator drain petcock located at the bottom of the radiator (verify exact side against the factory service manual). Allow coolant to drain into the pan until flow stops. Allow coolant to drain into the pan until flow stops. Close the petcock when draining is complete. If the thermostat housing is significantly below the radiator level, additional coolant will drain when the housing is opened.
2. 2

   Remove upper radiator hose
   Locate the upper radiator hose connection at the thermostat housing on the front of the engine. Use pliers to compress and slide the hose clamp away from the housing connection. Twist the hose to break the seal, then pull it off the thermostat housing neck. Have a shop towel ready to catch residual coolant.
3. 3

   Remove thermostat housing bolts
   Remove the bolts securing the thermostat housing to the engine (verify exact count and location against the factory service manual). Keep the bolts and note their positions for reinstallation. Keep the bolts and note their positions for reinstallation.
   Torque spec

   Thermostat Housing Bolts15 Nm (11 lb-ft)
4. 4

   Remove thermostat housing
   Pull the thermostat housing away from the engine block. If the housing is stuck due to old gasket material, gently tap it with a rubber mallet or carefully pry with a plastic scraper. Do not use excessive force or metal pry tools that could damage the sealing surfaces.
5. 5

   Remove old thermostat
   Lift the thermostat out of its recess (verify whether it seats in the engine-side pocket or the housing against the factory service manual). Note the orientation of the thermostat - the spring side faces toward the engine block, and the sensing element faces toward the radiator hose. The thermostat may have a small air bleed valve or jiggle pin at the top.
6. 6

   Clean mating surfaces
   Use a plastic or brass gasket scraper to carefully remove all old gasket material from both the engine block thermostat recess and the thermostat housing mating surface. Do not gouge or scratch the aluminum surfaces. Clean the surfaces with a shop towel and ensure they are completely free of debris and old gasket material. Inspect both surfaces for cracks or damage.
7. 7

   Install new thermostat
   Place the new thermostat into the recess in the engine block with the spring side facing into the engine and the sensing element (copper or wax pellet end) facing outward toward where the housing will mount. Ensure any air bleed valve or jiggle pin is positioned at the highest point (typically 12 o'clock position) to allow air purging during refill.
8. 8

   Install new gasket and housing
   Position the new thermostat housing gasket over the thermostat and align it with the bolt holes. Place the thermostat housing over the gasket and align the bolt holes. Start both housing bolts by hand to ensure proper thread engagement and gasket alignment before tightening.
9. 9

   Torque thermostat housing bolts
   Tighten the thermostat housing bolts in a crisscross pattern to the factory-specified torque (verify against the service manual; typically around 11 lb-ft / 15 Nm for aluminum housings). Do not overtighten as this can distort the housing or crack the gasket seal. Do not overtighten as this can distort the housing or crack the gasket seal.
   Torque spec

   Thermostat Housing Bolts15 Nm (11 lb-ft)
10. 10

    Reinstall upper radiator hose
    Slide the upper radiator hose fully onto the thermostat housing neck until it seats against the stop ridge. Reposition the hose clamp over the hose on the housing neck and tighten securely. Ensure the clamp is positioned at least 1/4 inch from the end of the hose.
11. 11

    Refill cooling system
    Using a coolant funnel at the radiator filler neck, slowly pour in the specified 50/50 ethylene glycol coolant mixture (verify total system capacity against the factory service manual — the V10 system holds significantly more than 3 quarts). Fill the radiator until coolant reaches the bottom of the filler neck. Pause periodically to allow air bubbles to escape. Squeeze the upper radiator hose several times to help purge trapped air. Continue filling as the level drops.
12. 12

    Burp cooling system
    With the radiator cap still off, start the engine and allow it to idle. Monitor the coolant level in the radiator and add coolant as needed as the thermostat opens and air is purged from the system. The upper radiator hose should become hot when the thermostat opens (approximately 195°F). Run the engine until the cooling fans cycle on, indicating the system has reached operating temperature and the thermostat has opened fully.
13. 13

    Final fill and cap installation
    With the engine at operating temperature and fans cycled, shut off the engine. Allow it to cool slightly, then top off the radiator to the bottom of the filler neck. Install the radiator cap securely. Check the coolant overflow reservoir level and fill to the COLD mark if needed.

Reassembly

1. Reassembly is completed during the procedure steps above
2. Ensure all hose clamps are properly tightened and positioned
3. Verify no tools or shop towels were left in the engine bay

Verification

• Start the engine and visually inspect the thermostat housing and upper radiator hose connection for coolant leaks
• Allow the engine to reach operating temperature and verify the upper radiator hose becomes hot, confirming thermostat is opening
• Verify cooling fans cycle on at normal operating temperature
• Check coolant level after the engine cools and top off if necessary
• Test drive the vehicle and monitor engine temperature gauge to ensure normal operating temperature is maintained
• Recheck for leaks after test drive and verify coolant level again after the engine cools

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