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Coolant Disappearing on 2016 LaCrosse - Thermostat Housing Leak?

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Mike T. · rep 0 · May 22, 3:53 AM · 1 replies · solved · Question

Vehicle: 2016 Buick LaCrosse Premium

Hello forum,

I'm having an issue with my 2016 Buick LaCrosse Premium (3.6L V6) where the coolant level in the reservoir keeps dropping. I've had to top it off a few times over the last month, and I can sometimes smell a faint sweet odor when the engine is warm, especially after driving. I don't see any puddles under the car, but I'm worried about a slow leak.

I've heard that the thermostat housing or water pump can be common failure points on these engines. Has anyone else experienced this with their LaCrosse? What should I be looking for, and is this something I can diagnose and fix myself, or should I take it straight to a mechanic?

No check engine light yet, and the temperature gauge seems normal, but I don't want to risk overheating.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:53 AM

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Coolant loss without visible puddles and a sweet smell are classic signs of a slow coolant leak, which can be tricky to pinpoint. Your suspicion about the thermostat housing or water pump on your 2016 Buick LaCrosse (3.6L V6) is well-founded, as these are indeed common failure points.

Common Leak Points to Inspect (DIY):

  1. Thermostat Housing: The plastic thermostat housing and its seals are prone to cracking or degrading over time, leading to leaks. Look for pink/orange crusty residue or wetness around the housing, especially where it connects to hoses or the engine block.
  2. Water Pump: The water pump on the 3.6L V6 is located on the front of the engine. Inspect the weep hole (a small hole on the pump body) for any signs of coolant leakage. Also, check the surrounding area for residue.
  3. Hoses and Clamps: Inspect all radiator hoses, heater hoses, and their connections for cracks, bulges, or loose clamps.
  4. Radiator: Check the radiator fins and end tanks for any signs of leakage, especially after the vehicle has cooled down.
  5. Coolant Reservoir: Sometimes the reservoir itself can crack, or the cap can fail.

DIY Diagnosis:

  • Visual Inspection: Perform a thorough visual inspection of all cooling system components, especially after the engine has reached operating temperature and then cooled down. Leaks often become more apparent as the system cools and contracts.
  • Pressure Test (Recommended): A cooling system pressure tester (can be rented from auto parts stores) is the most effective way to find slow leaks. Pump the system to the recommended pressure (check your owner's manual) and look for drops in pressure or visible leaks.
  • UV Dye: Add UV dye to your coolant and use a UV light to spot leaks, which can be very helpful for elusive drips.

When to See a Shop:

  • If you cannot locate the leak yourself, a professional can perform a more thorough diagnosis.
  • If the leak is from the water pump, as replacement can be involved and requires specific tools and knowledge.
  • If you notice a check engine light, especially codes like P0128 (Coolant Thermostat (Coolant Temperature Below Regulating Temperature)), which can indicate a failing thermostat or low coolant affecting its operation.
  • Any signs of white smoke from the exhaust (head gasket issue) or coolant in your oil (milky oil on dipstick) require immediate professional attention.
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