How are you doing? You will have to take it in and they will replace the thermostats again. But before doing so there are points to be looked at specially the coolant light always trigger.
Engine Coolant Loss with No Visible Leaks (Reseal Injector Sleeve)
- Excessive white smoke or a coolant type odor coming from the exhaust pipe, along with low coolant levels, may indicate coolant in the combustion chamber. Cause Condition may be caused by engine coolant entering the cylinder due to a dirty or damaged seal between the fuel injector sleeve and the cylinder head. Correction Perform the following diagnosis to determine the cause of the coolant loss.
External/Internal Coolant Leaks
- Verify that there are no external coolant leaks. Refer to the Loss of Coolant procedure in the Engine Cooling section of the Service Manual. If the vehicle is equipped with an Exhaust Gas Recirculation (EGR) system, inspect the EGR valve and intake system for evidence of internal coolant leakage. Replace the EGR cooler if any condition is found. Refer to Exhaust Gas Recirculation (EGR) Valve Cooler Tube Replacement procedure in the Engine Controls
- Disable the fuel system by removing the IGN 1 relay on C/K trucks or the IGN B relay on C4500/5500 trucks using the J 43244 Relay Puller Pliers. Disconnect the 4–wire glow plug control circuit connector from the glow plug relay/controller assembly. Remove the glow plugs. Refer to the Glow Plug Replacement — Bank 1 and the Glow Plug Replacement — Bank 2 procedures in the Engine Controls — 6.6L sub-section of the Service Manual. Inspect for evidence of coolant on the glow plug tips. Note any cylinders that show evidence of coolant leakage. Caution: Keep hands and face clear of glow plug holes while cranking. Hot liquid or gases may be expelled during cranking.
- Remove the fuel injector sleeves of the cylinders that show evidence of coolant leakage. Damage to this portion of the fuel injector sleeve may indicate a loose injector caused by improper tightening or a missing copper washer. A loose injector will allow the fuel injector and the fuel injector sleeve to bounce inside the cylinder head, resulting in coolant leakage to the cylinder. If damage is found, replace the affected components. Cylinder head or cylinder head gasket replacement will be required if worn out or damaged.
Hope this helps in giving you the insight why the coolant always fails. You may want to print this as well to let them know of the possibilities. Let's just hope that they might have gave you a factory defect thermostats and the new replacement resolves the issue for good.
Is there anything else I can add or help you with Terrance? I'll be standing by for your response.