BMW 6 Diesel Drop in Power and Boost System Warning Signs

Hey there! I faced nearly identical issues with my 2015 BMW 5 Series 520d last year. The symptoms match exactly what I experienced, power loss, stalling, that distinct whistling noise, and increased fuel consumption. In my case, it turned out to be a faulty wastegate valve in the turbocharger. Had it diagnosed at the garage where they confirmed the wastegate wasn't regulating boost pressure properly. It was quite a serious issue that needed immediate attention to prevent potential turbo damage. They replaced the entire wastegate actuator assembly. The repair wasn't quick, had to leave my car at the shop for two days while they sourced the parts and completed the work. But it solved all those issues completely, no more whistling, power's back to normal, and fuel consumption returned to standard. Given your symptoms, I'd strongly suggest getting it checked soon. Turbo-related issues tend to get worse if left unattended.

Thanks for sharing your experience, That's exactly what I needed to hear as the symptoms match perfectly. I'm actually planning to take it to a garage next week. Just curious, do you remember roughly how much you ended up paying for the wastegate actuator replacement? Also, has everything been running smoothly since the repair, or have you noticed any other issues popping up?

Hey again! Happy to give you an update! I actually just paid 860 € to get mine fixed, the mechanic found the exact same wastegate valve issue we discussed. Money well spent if you ask me, because my car's running like a dream now. Not a single problem since the repair about 8 months ago. The whistling sound completely disappeared, and the engine's got its full power back. Fuel consumption is back to normal too. I was actually surprised at what a difference it made, it's like driving a different car now! I'd definitely say go ahead with getting yours checked. That price I paid included both parts and labor, which seems pretty standard for this kind of repair. Just make sure you get it done soon, I learned that leaving these turbo issues too long can lead to bigger problems. Let me know how it goes when you get it fixed!

Thanks so much, Just wanted to update you, I got my car fixed last week and you were spot on! Took it to a new mechanic who diagnosed the exact same wastegate issue. Paid around 900 € for the whole job, which honestly feels worth it considering how much better the car runs now. The whistling's completely gone, and it's got its old power back. Funny thing, while I was at the shop, another BMW owner came in with similar problems. Made me feel better knowing it's a common issue! The mechanic was great too, really took the time to explain everything and even showed me the faulty part. Really appreciate your help in pointing me in the right direction. Car's running perfectly now, and my wallet's thanking me for fixing it before it turned into something bigger! Thanks again.