radiator fans come on very loud as soon as I start my 2017 buick lacrosse

Is the temperature gauge on the dash not working as well? Air conditioning not working? My first suspect is the coolant temperature sensor. Or the wiring going to the sensor. When the computer loses the signal from the coolant temperature sensor it assumes the engine is overheating and takes steps to prevent engine damage. The radiator cooling fans come on immediately at high speed and the air conditioning is disabled because it puts an additional heat load on the cooling system. Hope that helps! Jim

Cooling fans running when they shouldn't be is an indicator of something wrong with the engine management system, a code check might show what needs checked, if no codes then a live data scan is next.

If the radiator fans on your 2017 Buick LaCrosse are coming on loudly as soon as you start the car, there could be several reasons for this behavior. Here are a few possibilities: Normal Operation: In some vehicles, it is normal for the radiator fans to come on at a higher speed momentarily when the engine is started. This is often part of the system's self-check process. Coolant Temperature Sensor Issue: The coolant temperature sensor informs the engine control module about the temperature of the coolant. If the sensor is faulty or sending incorrect signals, it may cause the fans to run at higher speeds unnecessarily. Faulty Thermostat: A malfunctioning thermostat can cause the engine to run hotter than normal, triggering the fans to run at higher speeds to cool the radiator. Coolant Level: Check the coolant level in the radiator and reservoir. Low coolant levels can cause the engine to overheat, prompting the fans to work harder. Air Conditioning System: The radiator fans may also be influenced by the operation of the air conditioning system. If the air conditioning is set to maximum, the fans may run at a higher speed. Faulty Radiator Fan Relay: The radiator fan operation is often controlled by relays. A faulty relay can cause the fans to operate erratically or at higher speeds. Engine Overheating: If the engine is genuinely overheating, the fans will run at higher speeds to cool it down. This could be due to issues like a malfunctioning water pump, a clogged radiator, or a malfunctioning fan itself. Given the importance of the cooling system in maintaining proper engine temperature, it's advisable to have the vehicle inspected by a qualified mechanic. They can use diagnostic tools to check for fault codes, test the cooling system components, and identify the root cause of the loud fan operation. Addressing cooling system issues promptly is essential to prevent potential engine damage from overheating.

coolant thermostat stuck and temperature sensor are ususally bad... replace them . 3.6 v6 tends to have this problem with that symptom.