BMW Diesel Glow Plug Crisis: Cold Starts & Black Smoke

I faced similar issues with my 2020 BMW 5 Series diesel last winter. The symptoms were identical, glow plug warning, hard starts, black smoke, and check engine light. Took it to the garage and turns out the glow plug control module had corroded connections, plus two of the glow plugs were completely dead. The smoke and performance issues were directly linked to this. It's a serious problem that can damage your engine if left unchecked. In my case, they replaced the control module, all glow plugs (since the others were close to failing), and cleaned the connectors. The system needed a full reset afterward. Haven't had any issues since then. This isn't something you want to postpone, cold starts without proper preheating will definitely stress your engine components. Best get it checked at a specialized diesel workshop, the regular mechanics sometimes miss the underlying issues with these systems. My car starts perfect now, even in cold weather. No more smoke or warning lights.

Thanks for sharing that experience, it really helps as it sounds exactly like what I'm dealing with. Quick question: do you remember roughly how much you ended up paying for the whole repair? Also, has everything stayed running smoothly since then, or have you noticed any other issues pop up? I'm trying to get an idea of what I might be looking at cost-wise and whether this truly fixes the problem for good.

Hey there! Happy to update you on my BMW 5 Series situation. The fix wasn't as painful as I initially feared, ended up being just a faulty preheating control unit with a bad cable connection. Total bill came to 95 € to sort out the cable and connections, which was way less than I expected. Since getting it fixed, my car's been running like a dream! No more glow plug warnings, starts up beautifully even on chilly mornings, and that annoying black smoke is completely gone. Honestly, it's like having a different car, in a good way! The best part is that it's stayed perfect for months now. No warning lights, no starting issues, nothing. Looking back, I was probably making it sound scarier than it needed to be in my first post when I mentioned all those potential problems. Sometimes the simple fix is the right fix! Just make sure you get someone who knows their stuff with diesel engines, that's what made the difference in my case. Hope this helps with your decision!

Thanks so much for all that detailed follow-up! I actually took my car to a diesel specialist yesterday based on your advice. Just like your case, it turned out to be simpler than I feared. The mechanic found corroded connections in the glow plug system and a faulty sensor. Got everything sorted, including a proper system reset. The whole thing cost me less than expected, around 320 bucks total. What a relief, I was imagining thousands! The car's now starting perfectly, even this morning when it was pretty cold. No more black smoke either. Funny how we work ourselves up sometimes, thinking it's going to be this massive repair job. Really grateful for your help in pointing me in the right direction. Sometimes it really pays to get a second opinion from someone who's been there before. My previous mechanic was way off suggesting it might be a full engine rebuild! Thanks again for sharing your experience. You saved me from a lot of unnecessary worry!