BMW 8 Series Exhaust Flap Failure: Fix and Cost Guide

Had the same problem on my 2015 BMW M4 last winter. The exhaust flap actuator failed completely, similar symptoms to yours with the loud cold starts and no flap control. Got it checked at the garage, turned out the actuator motor was dead and had some corrosion build-up in the mechanism. They had to replace the entire actuator assembly and reset the system. It's not a critical issue for engine performance, but it's definitely annoying and should be fixed to prevent potential exhaust system damage. In my case, they also found that the vacuum lines were slightly damaged, which contributed to the problem. The whole repair took about half a day. Not the most complex fix, but definitely needed a professional touch. The car runs perfectly now, and the exhaust note is back to normal with full flap control.

Thanks for sharing your experience! This sounds exactly like what I'm dealing with. I'm glad to hear it was fixable and not something more serious with the engine. Would you mind sharing what the total repair cost was? Also, curious if you've had any similar issues pop up since getting it fixed?

Hey there! Happy to follow up about my M4's exhaust flap issue. Since you asked, the total repair came to 190 € to fix the defective exhaust flap, which included replacing the actuator and sorting out those vacuum lines I mentioned. I'm pleased to report that since getting it sorted at the mechanic, everything's been working perfectly fine, no more unwanted loud noises or control issues. The flaps are responding exactly as they should now, just like when the car was new. Haven't had a single problem with it since the repair, and it's been over a year now. For what it's worth, it was definitely money well spent. The car feels much more civilized, especially during those early morning starts when you don't want to wake the whole neighborhood! Let me know if you end up getting yours fixed, would be interesting to hear if you're dealing with the exact same issue.

Finally took my car to a different mechanic last week! What a relief, turned out to be exactly what you described. The actuator was completely shot, and they found some damaged vacuum lines too. Ended up paying a bit more than you did, around 250 € total, but honestly, it was worth every penny. The repair went smoothly, took them about 4 hours to fix everything. The mechanic was great, really knew his stuff about BMWs. The best part? No more embarrassing loud starts in the morning! The exhaust flaps are working perfectly now, and I've got full control back through the settings. Thanks again for your help, you really saved me from stressing too much about this. It's such a relief to have it sorted, and now I know where to go if anything else comes up with the car. Sometimes switching mechanics is the best decision you can make!