2017 LaCrosse Overheating at Idle: Low Coolant, What Type & How to Flush?

Hello Jessica,

Overheating at idle and low coolant are definite signs that your 2017 Buick LaCrosse needs attention. It's wise to address this promptly to prevent more serious engine damage. Your suspicion about the thermostat is also valid.

1. Coolant Type:

   • Your 2017 Buick LaCrosse with the 3.6L V6 engine requires Dex-Cool extended-life coolant. This is an orange/pinkish-red organic acid technology (OAT) coolant. It's crucial to use Dex-Cool and not mix it with other types of coolant, as this can lead to gelling and severe cooling system issues.
   • Always use a 50/50 pre-mixed solution or mix concentrated Dex-Cool with distilled water.

2. Coolant Flush DIY (General Steps - Consult Service Manual for specifics):

   • Safety First: Ensure the engine is completely cool before starting. Wear appropriate safety gear (gloves, eye protection).
   • Drain: Locate the radiator drain plug (petcock) at the bottom of the radiator and open it to drain the old coolant into a suitable container. You may also need to remove a lower radiator hose for a more complete drain.
   • Flush (Optional but Recommended): Once drained, close the drain plug. Fill the system with distilled water. Run the engine with the heater on high until it reaches operating temperature. Drain again. Repeat this process until the drained water runs clear. Some prefer to use a specific cooling system flush chemical during one of these cycles.
   • Refill: Close the drain plug. Fill the system slowly with the correct 50/50 Dex-Cool mixture. Leave the radiator cap off and run the engine with the heater on high, allowing air to purge from the system. Squeeze the upper and lower radiator hoses to help release air bubbles. Top off as needed.
   • Burp System: Drive the car, let it cool, and recheck the coolant level in the reservoir and radiator, topping off as necessary over the next few drive cycles.

3. Thermostat Issue:

   • Overheating at idle but cooling down while driving is a classic symptom of a failing thermostat that is stuck partially closed. It restricts coolant flow, especially when the water pump isn't working as hard (at idle). A faulty cooling fan could also contribute.
   • If you have access to an OBD-II scanner, a common code for a stuck-open or slow-to-open thermostat is P0128 (Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)). While your symptoms suggest it might be stuck closed or partially closed, this code can sometimes appear if the engine struggles to reach or maintain proper operating temperature.

When to See a Shop:

• If the overheating persists after topping off or flushing, or if you're uncomfortable with the thermostat replacement (which can be tricky on some models), it's best to take your LaCrosse to a professional. They can perform a pressure test to check for leaks, diagnose the cooling fans, and accurately replace the thermostat. Ignoring persistent overheating can lead to head gasket failure or other severe engine damage.