Buick GL6 Temp Gauge Dance: Thermostat Mystery

Had the same symptoms on my 2019 Buick Enclave last summer. The engine overheating issues and inconsistent temperature readings pointed directly to a faulty map thermostat. The coolant system would struggle to maintain proper temperature, swinging between too hot and too cold. Initially thought it was a coolant leak or water pump issue, but diagnosis revealed a defective electronic map thermostat causing erratic temperature control. The thermostat was sticking intermittently, preventing proper coolant flow regulation. This is actually a common failure point on these engines. Required complete thermostat assembly replacement along with a coolant system flush. Not a minor repair since accessing the thermostat housing meant removing several components. The symptoms disappeared completely after replacement. Would strongly recommend having it checked soon, as continued temperature fluctuations can lead to more serious engine damage over time. A professional shop with experience in Buick cooling systems should be able to properly diagnose and repair this issue.

Thanks for sharing your Enclave experience. Dealing with similar problems on my GL6 right now. The temperature sensor readings have been super unreliable, and the coolant system just wont regulate properly. Your description of the map thermostat failure matches my symptoms exactly. Good to know it was a complete fix, my mechanic keeps pushing for a full water pump replacement which felt like overkill. Did you remember roughly what the thermostat replacement cost you? Also curious if you have had any other cooling-related problems since the repair?

After getting the thermostat cooling circuit motor fixed in my Enclave, the temperature control issues cleared up completely. The repair cost came to around 350 Euro for the defective map thermostat replacement, which is pretty standard from what others have reported. The temperature sensor now shows consistent readings and the coolant system maintains proper regulation. No other cooling-related problems have surfaced in the months since the repair. The water pump has been working fine, so your instinct about that being overkill is probably right. This experience confirmed that inconsistent temperature readings and poor temperature control are classic symptoms of a failing map thermostat. Getting it diagnosed and fixed early helps prevent more extensive damage to the cooling system components. Going on 8 months now with perfect operation of the thermostat and stable engine temperatures. Would definitely recommend focusing on the thermostat rather than replacing other cooling system parts unnecessarily.

Thanks everyone for the input. Finally got my GL6 fixed last week after dealing with the engine overheating issues. Turned out you were right about the thermostat, took it to a different shop and they diagnosed a faulty map thermostat right away. The repair cost was reasonable at 375 for parts and labor. The mechanic showed me the old thermostat housing and it was clearly not functioning properly. They also did a cooling system flush while they were at it. Been driving for a week now and the temperature readings are finally stable. No more wild swings between hot and cold. The coolant level is staying consistent too, which is a relief. Glad I got a second opinion instead of going for that expensive water pump replacement the first shop suggested. Sometimes you just need to trust your gut and keep looking until you find the right diagnosis.