BMW Diesel Glow Plug Issues Causing Multiple Symptoms

I had almost identical symptoms with my 2008 BMW 3 Series 320d. Based on my garage visit last month, I can tell you this is likely more than just the glow control unit. The constant preheating light combined with starting issues and heavy smoke pointed to faulty glow plugs in my case. Three out of four glow plugs were completely shot, and the wiring harness had significant corrosion at the connections. The mechanic also found that the glow plug control module had water damage. This was actually a serious issue that needed immediate attention, as continuing to drive would've led to more engine damage and worse fuel economy. The repair involved replacing all glow plugs, the wiring harness, and the control module. Since then, the car starts perfectly, even in cold conditions, and there's no more smoke during acceleration. For your car, I'd strongly suggest finding a BMW specialist rather than a general mechanic, as they'll know exactly what to look for with these common diesel issues.

Thanks for sharing your experience. Had very similar problems with my old Beemer too. Got it sorted at last but what a headache that was! Just wondering, would you mind sharing roughly how much you ended up paying for all that work? Also, has everything been running smoothly since the repair? My symptoms are pretty much identical to what you described, so I'm trying to budget for what's coming. Really helpful to hear from someone who's been through it already.

Hey! Just to follow up on your question, actually, I got lucky with mine. After taking it to the specialist, turned out it was just the glow control unit's cable connection that was playing up, not the whole mess I initially thought it was. Only set me back 95 € to fix the dodgy connection, which was a massive relief compared to what I was expecting! Everything's been running like a dream since then. No more drama with the preheating light, starts up perfectly even on those chilly mornings, and the smoke issue during acceleration is completely gone. Honestly wished I'd gotten it checked sooner instead of worrying about worst-case scenarios. Fingers crossed yours turns out to be something simple too, but yeah, definitely get it checked by someone who knows these BMWs inside out. Even if it does end up being more extensive like I first thought with the glow plugs and wiring, at least you'll know it's done right. Just make sure they properly diagnose it first, could save you a bunch of money like in my case!

Just got back from the mechanic, and wow, what a journey this has been! Turns out it was actually a combination of issues. The main culprit was indeed the glow plugs, but there was also a damaged sensor that was causing the preheating light to stay on. Cost me a bit more than your repair, around 400 for parts and labor, but honestly, it was worth every penny. The mechanic I found was brilliant, really knew his stuff with BMWs. He showed me the old parts and explained everything clearly. You were spot on about going to a specialist, they diagnosed it properly first instead of just throwing parts at the problem. Car's running beautifully now, starts right up in the cold, no more smoke, and passed the emissions test with flying colors. Thanks again for sharing your experience, it really helped me know what to expect and pushed me to get it sorted properly. Definitely feeling relieved now that it's all fixed up!