BMW 7 Diesel: Overheating + No Heat = Bypass Valve Issue?

Hey there! I've got some experience working on BMWs, I had a similar issue with my 2004 BMW 5 series diesel (had a couple of BMWs, including a 3 series). I faced almost identical symptoms, overheating and no cabin heat. Turned out my car had a previous repair where they didn't properly bleed the cooling system after replacing the water pump. The air pockets caused the overheating and the heat issues. The workshop sorted it out for free since it was their mistake from the earlier repair. Can you share what error codes you're getting? Also, have you had any recent cooling system work done? This info would help narrow down if you're dealing with the same thing.

Thanks for sharing your experience! The error codes I'm getting are P0128 and P2181. Last service was just 2 weeks ago, and they did work on the cooling system. My BMW is at 39495 KM, so I was surprised to face these issues so soon after maintenance. I'm starting to think they might have messed up the bleeding process too. I'll definitely bring this up with the workshop. Did your car also show any warning lights on the dash before the overheating got serious?

Hey again! Yeah, definitely sounds similar to what I experienced. With my 5 series, I actually did get warning lights, first the coolant temperature light started flashing, and then the check engine light came on. Those exact same error codes too, P0128 and P2181. After my service experience, I'm pretty convinced you're dealing with the same air pocket issue I had. At first, I thought it was the bypass valve too, but the symptoms match perfectly with improper bleeding. My car was around 45000 KM when it happened, so pretty close to your mileage. The workshop should definitely take responsibility if they worked on the cooling system just 2 weeks ago. When they fixed mine, they had to do a proper vacuum-assisted bleeding process, took them about an hour. After that, all the symptoms disappeared completely, cabin heat came back, no more overheating, and the error codes cleared up. Just a heads up, don't let them charge you for this. Since they did recent cooling system work, this should be covered under their service warranty. If you want, you can even mention my case as an example. These BMWs are really sensitive to air in the cooling system, and proper bleeding is crucial after any cooling system work. Keep us posted on what they say! Really interested to hear if it's the same issue.

Thanks so much for all the detailed info! You're right, I just called the workshop and they admitted they might have rushed the bleeding process during the last service. They've agreed to check it out under warranty tomorrow morning, and they'll use their vacuum-assisted bleeding equipment. Honestly, I'm relieved it's probably not the bypass valve, that would've been a much more expensive fix! Really appreciate you sharing your experience. It's given me the confidence to push back on the workshop and know what to expect. I'll probably keep an eye on the temperature gauge for a while after getting it back, just to be safe. Will definitely update you once it's sorted. Thanks again for helping a fellow BMW owner out!