RS6 Heater Core Failure, Common Fix Solutions

Had the same heating issues on my 2017 RS4. The car heating would barely work even with temperature set to maximum. After thorough diagnostics, it turned out the automotive valve that controls coolant flow to the heater core was failing. The valve was stuck in a partially closed position, restricting proper coolant flow through the heating system. The fix required removing several components to access the water valve assembly. The connector pins showed significant corrosion, and the valve itself had internal wear. This is a known weak point that can develop issues around 150000 KM. With your symptoms and error codes, definitely have a qualified shop check both the heater core and water valve operation. Engine overheating is not typically related to this specific issue, but the malfunctioning valve can cause inconsistent temperature control. The repair was fairly involved due to component location, but not particularly complex from a technical standpoint. Worth fixing properly rather than attempting temporary solutions that might lead to bigger problems. Your RS6 likely uses a similar heating system design, so the diagnosis process should be comparable.

Thanks for sharing your experience with that RS4 heating problem. What you described matches my car symptoms exactly. I think I will get my RS6 checked at a different shop soon with focus on the valve blockage and heater core inspection. How much did the water valve replacement end up costing you? Just trying to get a rough idea of what to expect. Also wondering if you had any other cooling or heating issues pop up since getting it fixed?

Thanks for asking about the follow-up. Since replacing the automotive valve in my RS4, the heating system has worked flawlessly. The valve blockage turned out to be caused by a faulty electrical connection rather than mechanical wear as initially suspected. The final bill came to 95 Euro for fixing the cable connection to the water valve. Much cheaper than expected since no parts needed replacement. The engine coolant flow returned to normal immediately after the repair. The cooling system has been performing perfectly for the past 8 months with no temperature fluctuations or heating issues. Regular coolant level checks show everything is staying where it should be. Your RS6 might have a different underlying cause, but starting with a valve inspection is definitely the right approach. Having a thorough diagnostic done by a qualified shop will help pinpoint whether its an electrical or mechanical issue with the valve.

Thanks for all the great input. I took the car to a different shop yesterday and showed them the information about checking the valve blockage and heater core. Their diagnostic confirmed a failing water valve, just like you experienced. The coolant leak they found was minor but had damaged some of the electrical connections. Total repair came to 780 Euro including parts, labor and a full cooling system flush. More than your repair but still reasonable considering the work involved. The car heating is now working perfectly again. The shop also showed me the old valve which was pretty corroded. Really glad I caught this before it caused more serious problems with the cooling system. Will keep monitoring everything but feeling confident the issue is properly resolved now. Good to be back to normal cabin temperatures during these cold days.