Thermostat

This procedure covers the removal and replacement of the thermostat on a 2014-2018 Chevrolet Silverado 1500 with the 5.3L V8 L83 engine, including coolant draining, housing removal, and system refilling.

Warnings

Tools required

Parts

• Engine thermostat assembly × 1 — ACDelco 131-158 or equivalent
• Thermostat housing O-ring seal × 1 — Use OEM specification
• Thread sealant (if removing coolant temp sensor) × 1 — Permatex 59214 or equivalent

Fluids

• ACDelco DEX-COOL (Orange) — 2 qt

Preparation

1. Ensure the 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 located at the bottom of the radiator on the driver side
4. Remove engine cover by pulling upward on the front edge to release clips, then lifting off
5. Locate the thermostat housing on the driver side front of the engine block where the lower radiator hose connects

Procedure

1. 1

   Drain coolant from radiator
   Open the radiator drain petcock by turning counterclockwise. Allow coolant to drain into the pan until the flow stops. The coolant level only needs to be below the thermostat housing. Close the petcock hand tight when finished.
2. 2

   Remove lower radiator hose from thermostat housing
   Locate the lower radiator hose connection at the thermostat housing. Use a flathead screwdriver or hose clamp pliers to loosen the hose clamp. Slide the clamp down the hose away from the housing. Twist and pull the hose off the thermostat housing outlet. Additional coolant will drain; have a towel or drain pan positioned to catch it.
3. 3

   Disconnect coolant bypass hose
   Identify the smaller coolant bypass hose connected to the side of the thermostat housing. Loosen the hose clamp and slide it away from the housing. Remove the bypass hose from the housing nipple. Keep track of the hose clamp position for reassembly.
4. 4

   Remove thermostat housing bolts
   Using a 10mm socket, remove the two bolts securing the thermostat housing to the engine block. Note the bolt locations as they secure the housing to the water pump inlet. Remove the bolts completely and set aside.
5. 5

   Remove thermostat housing and thermostat
   Pull the thermostat housing away from the engine block. The thermostat will either stay in the housing or remain in the engine block recess. Remove the thermostat from whichever location it is in. Note the orientation of the thermostat spring (spring side faces into the engine block). Remove and discard the old O-ring seal from the housing groove.
6. 6

   Clean mating surfaces
   Using a plastic scraper, carefully clean all gasket material and residue from both the thermostat housing mating surface and the engine block mating surface. Spray with brake cleaner and wipe clean with a shop towel. Ensure no debris falls into the engine coolant passages. Both surfaces must be completely clean and smooth.
7. 7

   Install new thermostat and O-ring
   Lightly lubricate the new O-ring with coolant and install it into the groove on the thermostat housing. Insert the new thermostat into the recess in the engine block with the spring side facing into the engine. Ensure the thermostat is fully seated in the recess and properly aligned.
8. 8

   Install thermostat housing
   Position the thermostat housing over the thermostat and align it with the bolt holes on the engine block. Install both housing bolts and hand tighten. Using a torque wrench, tighten the bolts in a criss-cross pattern to specification.
   Torque spec

   Thermostat Housing Bolts15 Nm (11 lb-ft)
9. 9

   Reconnect coolant hoses
   Slide the lower radiator hose onto the thermostat housing outlet until it is fully seated against the bead. Position the hose clamp over the connection point and tighten to specification. Reconnect the bypass hose in the same manner, ensuring the hose is fully seated before tightening the clamp.
10. 10

    Refill cooling system
    Locate the coolant bleed screw on top of the thermostat housing or nearby coolant passage. Open the bleed screw approximately 2-3 turns. Fill the radiator through the radiator cap opening with DEX-COOL coolant until coolant flows from the bleed screw without air bubbles. Close the bleed screw to specification. Continue filling the radiator to the proper level, then fill the coolant reservoir to the COLD fill line.
11. 11

    Burp cooling system
    With the radiator cap still off, start the engine and allow it to warm up to operating temperature (thermostat opens). Watch the coolant level in the radiator and add coolant as needed. Gently rev the engine to 2000-2500 RPM several times to help purge air from the system. Monitor the bleed screw area and upper hoses; if air bubbles are visible, carefully crack open the bleed screw briefly to release trapped air, then retighten.
12. 12

    Final system check
    Once the engine reaches operating temperature and the upper radiator hose is hot, shut off the engine. Allow the system to cool for 15-20 minutes. Check the coolant level in both the radiator and reservoir; top off as necessary. Inspect all connections for leaks. Reinstall the radiator cap securely. Reinstall the engine cover by aligning the rear tabs and pressing down on the front clips until they snap into place.

Reassembly

1. Ensure all hose clamps are positioned correctly over the hose beads and tightened to specification
2. Verify the bleed screw is closed to proper torque to prevent leaks
3. Double-check that the radiator drain petcock is closed hand tight

Verification

• Start the engine and verify it reaches normal operating temperature (approximately 195-220°F)
• Check that the upper radiator hose becomes hot, indicating the thermostat has opened
• Verify there are no coolant leaks at the thermostat housing, hose connections, or bleed screw
• Confirm the heater produces hot air when set to maximum temperature
• Check the coolant level in the reservoir after the engine cools; it should be at the COLD fill line
• Monitor engine temperature gauge for the first few drives to ensure proper thermostat operation and no overheating occurs

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

Chasing one of these codes and not sure which part is guilty? Ask a master mechanic about YOUR car →

More procedures for this vehicle