RS6 Thermostat Drama: Hot Running But Slow Warm-Up

Had a similar situation with my 2017 Audi S6. The symptoms matched exactly, slow warm-up periods followed by overheating during regular drives. The thermostat was indeed the culprit, specifically a defective map thermostat in the coolant system that wasnt regulating temperature control properly. The repair involved replacing both the thermostat and thermostat housing since they come as one unit in these engines. Its a serious job because the thermostat location requires removing several components to access it. The water pump was also inspected during the repair as its often related to cooling system issues. Getting it fixed was crucial, running with a faulty thermostat risks engine damage from temperature fluctuations. Left untreated, it could lead to warped cylinder heads or gasket failures. The repair process took about 6 hours at the shop. Would strongly recommend having it diagnosed and fixed at a certified shop since the cooling system on these engines requires specific knowledge and proper diagnostic tools to verify the thermostat operation.

Thanks for sharing your experience. My RS6 had almost identical symptoms and I went ahead with the repair last month. The temperature sensor readings were all over the place which confirmed the thermostat housing needed replacement. Curious how much the total repair cost was in your case? Mine came to 850 Euro including parts and labor. Also wondering if youve experienced any coolant leaks or other cooling fan issues since the fix? My car runs perfectly now but always good to know what to watch out for.

Good to hear you got it sorted. After seeing the mechanic, my issue was indeed the Thermostat cooling circuit motor which was completely defective. The total repair came to 350 Euro for the Defective map thermostat replacement, which is pretty standard based on what other owners have reported. The temperature control has been flawless since the fix, no coolant leaks or any other cooling system problems to report after 30000km. The water pump and other components were all checked during the repair and found to be in good condition. Your cost seems a bit high at 850 Euro, but prices can vary depending on parts availability and labor rates. The important thing is your car is running properly now. Regular coolant level checks are still recommended just to catch any potential issues early.

Thanks for the input. Finally got this resolved at an independent shop that specializes in German cars. The cooling system diagnosis confirmed a failing thermostat and they found a small coolant leak from a cracked hose while doing the repair. Total bill came to 850 Euro which covered the new thermostat housing, hose replacement, fresh coolant, and about 5 hours of labor. They also performed a full system pressure test to ensure everything was sealed properly. Engine temperature now stays perfectly steady and warm-up time is back to normal. The shop walked me through their full diagnostic process which made me feel much better about the repair compared to my previous experience. Would definitely recommend getting these cooling system issues checked out quickly, waiting would have likely led to bigger problems. Really glad to have this sorted before summer.