RS6 Bypass Valve Mystery Causing Overheating Headaches

Had a similar issue with my 2020 RS4. The engine overheating warning came with coolant leak symptoms. Initial diagnosis pointed to the bypass valve, but during repairs we discovered the real culprit was a damaged air intake system causing incorrect readings. The air intake damage had created a chain reaction affecting the cooling system performance. When left unchecked, these symptoms can lead to serious engine damage and costly repairs. The overheating was actually a secondary issue stemming from the compromised air intake system. Main repair steps included: Full diagnostic scan, Air intake system replacement, Bypass valve inspection and cleaning, Coolant system pressure test, Temperature sensor verification This was classified as a serious repair requiring immediate attention. Delaying repairs in these cases typically leads to more extensive damage. The coolant leak combined with engine overheating indicates a complex issue that needs professional diagnosis with proper equipment. Would strongly recommend getting a full diagnostic scan rather than focusing solely on the bypass valve. These symptoms often mask underlying problems that affect fuel efficiency and engine performance.

Thanks for sharing that repair experience. Sounds similar to what I faced with my RS6 last summer. Had the same engine overheating warnings and power loss issues. The mechanic first suspected the bypass valve too, but it turned out to be a faulty thermostat causing engine stalling and temperature control problems. Before we go deeper into comparing notes, can you share what the final repair cost was in your case? Also, curious if youve had any recurring issues since the fix? My repair was several months ago but Id like to know if I should watch for any particular warning signs.

Thanks for asking about the costs. The repair actually ended up being completely covered at 0 Euro since the damaged air intake system was traced back to an incorrectly performed previous service. When they fixed the air intake, the bypass valve malfunction resolved itself since it was just a consequential error. Since the repair, the engine overheating warnings have completely disappeared and fuel efficiency has returned to normal. The exhaust system is also performing better now that the air flow is properly regulated. Its been running perfectly for over 8 months without any warning lights or temperature issues. For your RS6, definitely monitor the coolant levels regularly and watch for any changes in engine temperature behavior. A properly functioning bypass valve should maintain consistent temperatures, especially during hard acceleration or extended highway driving.

After your advice, I finally got the RS6 properly diagnosed and fixed. A complete inspection revealed the thermostat and vacuum system needed replacement. The repair cost came to 2800 Euro total, including parts and labor. The car repair process took 3 days but solved both the engine overheating and power loss issues completely. The mechanic I found specialized in performance vehicles and did a thorough job documenting all the problems. They also performed a complete cooling system flush which helped restore proper engine temperature regulation. Been driving for about 2 weeks now and the temperature stays perfectly stable. No more warning lights or error codes. The fuel efficiency has actually improved compared to before, probably because the engine is running at optimal temperature now. Really glad I got a second opinion instead of rushing back to the previous shop. Sometimes paying a bit more for the right diagnosis saves money in the long run by preventing repeated repair visits.