BMW 6 Diesel Heating Woes: Faulty Water Valve Alert

Hey there! I've got some experience working on cars and had a similar issue with my 2017 BMW 5 series diesel (had a 7 series before that). The symptoms you're describing sound exactly like what I faced, inconsistent heating and those annoying error codes. Took it to my workshop and turns out it was just a faulty connection in the heating control module wiring. They found a loose cable and some corrosion on one of the plugs. Total bill came to 95 Euro for diagnosis and fixing the connection. Before you head to the workshop though, could you share: Which error codes you're getting? Does the issue happen right after starting the car or after driving for a while? Are you hearing any unusual sounds from the heating system? This info would help compare if it's the same problem I had. Might save you some diagnostic time at the shop!

Thanks for sharing your experience! My car has 42183 KM on the clock and just had its service last month. The error codes I'm getting are P0597 and P0599. The heating issue starts immediately after turning on the car, and there's a slight humming noise from behind the dashboard. It's definitely more noticeable when adjusting the temperature controls. I'll keep the wiring issue in mind when I take it to the workshop. Really hoping it's just a connection problem like yours and not the water valve, heard those repairs can get pretty expensive! Did you notice any humming sounds when you had your issue?

Thanks for the error codes, yup, those are different from what I had with my BMW. In my case, I only had the P0599 code. The humming noise is interesting because I didn't have that with my wiring issue. Actually, now that you mention the symptoms in detail, I'm starting to think it might really be the water valve. When I previously owned a BMW 7 series, it had a similar humming noise, and it turned out to be a failing water valve. The repair was pricier than my recent wiring fix, around 400 Euro for parts and labor. But honestly, it was worth every penny because the heating worked perfectly afterward. The water valve controls the coolant flow to your heater core, and when it starts failing, you get exactly what you're describing, uneven heating and that humming sound. Given your car's mileage and the specific error codes, I'd bet money on the water valve being the culprit. Quick tip though, when you take it in, ask them to check the electrical connections to the valve first. Sometimes the valve itself is fine, and it's just the connector that's gone bad. Could save you some money if you're lucky. Let me know what the workshop finds. Really interested to hear if it matches what I experienced with my 7 series.

Thanks so much for the detailed response! That's really helpful, especially about the water valve issue you had with your 7 series. The humming noise matching your previous experience has me concerned, but I'm glad you mentioned checking the electrical connections first, definitely going to bring that up at the workshop. I've actually just booked it in for next week. The 400 Euro repair cost you mentioned isn't great news, but at least I know what I might be looking at price-wise. Better to fix it now than let it get worse, I suppose. Really appreciate you sharing both your experiences, the wiring issue with your 5 series and the water valve problem with your 7 series. Gives me a good idea of what to expect. I'll make sure to update you after the workshop visit. Fingers crossed it's just the connections, but I'm mentally prepared for the water valve replacement after what you've shared. Thanks again for all the insights!