Audi A3 Engine Cooling Failure with Temperature Issues

As an A4 2014 TDI owner, I faced nearly identical thermal management issues last year. The symptoms match what you describe, delayed engine warm-up and erratic temperature gauge readings. The check engine light typically indicates the engine control unit detecting inconsistent cooling system data. While a blocked cooling grille can cause overheating, your symptoms point more toward a faulty coolant temperature sensor or damaged wiring harness. The sensor transmits incorrect readings to the ECU, leading to poor thermal management and engine performance. In my case, diagnostic testing revealed a blown fuse and corroded wiring to the coolant temperature sensor. The repair involved replacing both the sensor and associated wiring harness. This was a serious issue requiring immediate attention, as continued driving could have led to engine damage from improper temperature regulation. The automotive cooling system on VAG diesel engines is particularly sensitive to sensor malfunctions. I recommend having a complete diagnostic scan done, focusing on the temperature sensor circuit and cooling system components. Car overheating issues often start with electrical problems rather than mechanical blockages. Before replacing parts, ensure your mechanic checks: Coolant temperature sensor functionality, Wiring harness condition, Related fuses, ECU error codes specific to the cooling system

Thanks for sharing your experience with those engine cooling issues. The symptoms you described match exactly what I dealt with on my A3. After seeing your detailed reply, I am now quite sure it was also the temperature sensor in my case. The erratic readings and slow warm-up were really concerning. Did you remember roughly how much the repair ended up costing? Also curious if you had any radiator blockage or cooling system problems since getting it fixed? Just want to make sure I am not overlooking anything when I take it to the shop.

After getting everything properly diagnosed and fixed at the shop, I can confirm it was indeed similar temperature sensor issues. The mechanic found a defective fuse that cost 52 Euro to replace. They also discovered and cleared a partially restricted cooling grille, which was affecting the overall thermal management system. Since completing those repairs several months ago, the engine cooling system has worked flawlessly. No more erratic temperature readings or extended warm-up times. The check engine light has stayed off and the engine maintains proper operating temperature. I recommend having them perform a full cooling system inspection while they are checking the sensor. In my experience, these automotive cooling problems rarely occur in isolation. Getting everything checked at once can prevent future issues from developing. The investment was worth it for the peace of mind, knowing the engine overheating risk has been properly addressed. Regular maintenance of cooling components is crucial for these engines.

Just got back from the mechanic and wanted to update everyone. The diagnosis confirmed it was indeed the temperature sensor causing my engine cooling problems. Total repair cost came to 430 Euro including parts and labor. They found the old sensor was completely shot and had damaged some surrounding wiring. While checking the cooling system, they also cleaned out some debris from the radiator grille and replaced a worn coolant hose they spotted. Better to fix it all at once than risk car overheating issues later. The car runs perfectly now, warms up normally and shows steady temperature readings. No more check engine light either. Really glad I got this sorted before any serious engine damage occurred. Thanks for helping point me in the right direction with the diagnosis.