BMW 8 Diesel: Boost Issues and Whistling Noise

Hey there! I have some experience working on BMWs. Actually, had a similar issue with my 2016 BMW 6 Series diesel last year. My M550d recommended his workshop when I got that same temperature sensor error code, power loss, and whistling sound. Turned out the cable connection to the charge air temp sensor was damaged and loose. The workshop fixed it pretty quickly, paid around 95 Euro for the repair job. Car's been running perfectly since then. Before I share more details that might help, could you share: Which 8 Series variant you have? How many miles/kilometers on the clock? Does the whistling get louder at higher RPMs? Let me know and I'll try to give you more specific advice based on my experience.

Thanks for sharing your experience! I've got the 840d. The whistling definitely gets more noticeable at higher RPMs. Just had my service two months ago and currently at 135,877 KM. Your issue sounds really similar to what I'm experiencing. Did you notice any smoke or unusual exhaust before getting it fixed? Good to hear it wasn't too expensive of a repair in your case, gives me some hope! Think I'll get it checked out soon before it potentially gets worse.

Hey again! Yes, your symptoms sound exactly like what I experienced with my 6er. Actually, now that you mention the exhaust, I didn't notice any smoke, but there was this subtle performance lag, especially when trying to accelerate quickly. It's pretty typical for these sensors when they start acting up. Just to add to my previous reply, I actually drove with the issue for about a week before getting it fixed (probably not the smartest move). The whistling got progressively louder, and the power loss became more noticeable. The repair shop told me I was lucky because driving too long with this issue can sometimes affect other components in the charge air system. Since you're at 135K km, it's right around the time these sensors can start giving trouble. Mine happened at about 120K km. After the fix, the difference was like night and day, full power restored and that annoying whistle completely gone. Quick tip, when you take it in, ask them to check the entire charge air system while they're at it. My mechanic did a thorough inspection and found a slightly worn clamp that could've caused problems down the line. Better safe than sorry with these high-performance engines!

Thanks so much for the detailed follow-up! Really appreciate you sharing those extra details about your experience. I'll definitely take your advice about getting the whole charge air system checked, that's a great tip about the clamps too. Actually just called a workshop and booked it in for tomorrow morning. Don't want to risk causing any additional damage by waiting too long. Your experience has been super helpful, especially knowing the dramatic improvement you got after the fix. Will probably need to resist driving it much until tomorrow, even though it's tempting to just push through. Better to play it safe with these engines, like you said. Thanks again for all your help, will try to update the thread once I get it sorted!