SQ5 Cooling System Troubles: Slow Warmup & Temp Issues

Having owned a 2018 S4 with similar thermal management issues, I can share some relevant experience. While I have moderate experience with car maintenance, this specific issue required professional help. The symptoms you describe match what I encountered, inconsistent temperature readings and slow warmup cycles. Initially I also thought it was related to the cooling grille or radiator blockage, but it turned out to be a blown fuse controlling the engine management system and temperature sensors. My workshop diagnosed it within an hour and the fix was straightforward, replacing the faulty fuse that was causing erratic temperature readings and affecting the engine cooling system. Total cost was 52 Euro including diagnostic time. However, before jumping to conclusions, could you share: Are there any other warning lights besides the check engine light? Does the temperature fluctuate or just read consistently low? Have you noticed any changes in fuel consumption? When was your last cooling system service? These details would help determine if your issue is similar or potentially related to other automotive cooling components that need attention.

Thanks for your input. My car has 190389 KM and last service was done in December 2022. To answer your questions, the temperature gauge shows unstable readings that fluctuate between normal and slightly elevated. No additional warning lights besides the check engine light. Fuel consumption increased by about 2L/100km recently. Just checked under the hood and noticed significant debris buildup around the radiator grille, which might be causing restricted airflow. The cooling system definitely seems affected as the engine fan runs longer than usual after parking. Would cleaning the grille area be a good first step before taking it to a workshop? Want to avoid unnecessary repair costs if its just debris causing these symptoms.

Based on your description and mileage, this does seem more complex than my initial fuse issue. While I also noticed debris in my S4's cooling grille, the symptoms you describe, especially the increased fuel consumption and unstable temperature readings, suggest this could involve multiple components of the engine cooling system. I tried cleaning my grille first too, but the erratic temperature gauge persisted. A professional inspection revealed a failing thermostat alongside the fuse problem. The total repair came to 380 Euro including parts and labor. Given your car has similar symptoms but more pronounced issues with the cooling system, I recommend: 1. Clean the cooling grille and radiator area to improve airflow 2. Have the engine cooling system professionally pressure tested 3. Get the check engine light codes read, this will pinpoint if its a sensor, thermostat, or other component The fan running longer after parking is particularly concerning, as this indicates the engine overheating protection is activating more frequently. In my case, delaying the repair led to more extensive damage to other cooling components. Would you consider sharing the check engine codes? This could help narrow down whether your issue mirrors my thermostat failure or points to different cooling system components.

Thanks everyone for the suggestions. After getting the check engine codes read at a local parts store, it shows P0128 (coolant thermostat malfunction) and P0116 (engine coolant temperature circuit range/performance). The radiator blockage turned out to be a contributing factor, but not the main issue. Cleaned the cooling grille and surrounding area, which helped airflow but didnt resolve the temperature fluctuations. Given the codes and symptoms, I will book it in for a proper thermal management system inspection. Really hoping its just the thermostat like your case and not something more serious with the engine cooling components. Will update once I get the workshop diagnosis. The car runs fine otherwise, so catching this early should prevent any major cooling system damage. Guess I will budget around 400 Euro based on your repair costs, though prices may have changed since then. At least cleaning the radiator grille myself saved some diagnostic time.