BMW 8 Series Overheating: Bypass Valve or Something More?

Hi there! I can relate to your situation as I had similar issues with my 2017 BMW 7 Series. I'd say I have some experience working with cars, mainly basic maintenance and troubleshooting. My car showed identical symptoms, overheating engine, cold cabin, error codes, the works. After taking it to my regular workshop, they discovered it was actually connected to a previous repair where they had replaced the water pump. They hadn't properly bled the cooling system, which caused these issues. Thankfully, they fixed it at no cost since it was their mistake. Before I can share more specific advice, could you share: What's your exact engine variant? Have you had any recent cooling system repairs? Are you noticing any coolant loss? What's the specific error code you're getting? These details would help me give you more targeted advice based on my experience.

Thanks for sharing your experience! My car has been super reliable until now (62773 KM on the clock since my last service). I'm running the gasoline engine variant, and funny enough, I did have the water pump replaced about two months ago at a local shop. Started noticing a small coolant puddle under the car last week, but didn't think much of it. Haven't checked the specific error code yet, need to grab my OBD reader from my friend. Really appreciate your insight about the bleeding issue. Maybe I should head back to that shop and have them check if they did the procedure correctly. Sounds like it could be the same problem!

Hey again! this is like déjà vu, your situation sounds exactly like what I went through! After reading your reply, I'm even more convinced we had the same issue. My 7 Series also started showing these symptoms shortly after a water pump replacement. Let me tell you something, when I noticed that small coolant puddle, I did the same thing and brushed it off. Big mistake! The improper bleeding was actually causing air pockets in the system, which led to that coolant leak and all those other symptoms you're describing. Since you mentioned you had the water pump done two months ago, I'd definitely head back to that shop ASAP. Here's what I learned from my experience, proper bleeding of the cooling system is super critical on these BMW engines, and it's not as straightforward as on other cars. My mechanic admitted they initially rushed through the procedure, thinking it was like any other car. Given your mileage and maintenance history, I really doubt it's a bypass valve issue like you initially suspected. I'd bet good money it's related to that recent water pump job. When you go back, make sure they do a proper pressure test too, that's how they found my leak spots. Keep me posted on what you find out! Would love to know if it turns out to be the same problem I had.

Thanks so much for all this detailed info! You've actually made me feel a lot better about the whole situation. I just called the shop and they can get me in tomorrow morning, told them about the possible bleeding issue and they seemed pretty receptive. You're right, I shouldn't have ignored that coolant puddle. Guess we all learn these things the hard way! Really appreciate you sharing your experience, it's saved me from stressing about potentially bigger problems. I'll definitely get them to do that pressure test you mentioned too. Will let you know how it goes, but feeling much more confident now that I know what to ask them to check. Thanks again for taking the time to help out!