BMW i3 Hybrid Cooling Issues: Thermostat Warning Signs

Hey there! I've got some experience with BMWs (moderate expertise level). Had a very similar issue with my 2019 BMW i8 Hybrid last winter. The symptoms you're describing sound exactly like what I went through, sluggish warm-up, poor fuel economy, and inconsistent cabin heating. Took it to my workshop and, after diagnostics, turned out it was indeed a defective map thermostat. The repair took about 4-5 hours, set me back around 350 Euro, but solved all those issues completely. The i8 has been running perfectly since then, and my 530e-driving had the same fix for similar symptoms. Mind sharing: Any warning messages on your dash? Current mileage? How long have you noticed these symptoms? I can probably give you more specific advice once I know these details, as these BMWs have pretty similar cooling systems.

Thanks for the detailed response! I've been noticing these issues for about 3 weeks now. On my dash, I get an occasional "Check Engine" warning, but it's not constant. My i3 just hit 82152 KM and had its last service 4 months ago. Really helpful to hear that fixing the map thermostat sorted out similar problems for you. Gives me some hope it won't be too complicated. Did you notice any particular sounds or smells before getting it fixed? Just trying to confirm if I'm dealing with the same thing before booking it in.

Hey again! Yeah, now that you mention it about sounds and smells, my i8 had these exact same symptoms around the 85000 KM mark. And I totally get why you're asking about sounds and smells, I remember being super alert to any unusual signs before getting mine fixed. Actually, I did notice a sort of sweet-ish smell occasionally, especially when the engine was warming up. I later learned this was the coolant getting a bit too hot due to the faulty thermostat. Didn't really hear any weird noises though, which is probably good because that would've meant bigger problems. Since you asked, my experience turned out to be pretty straightforward once I got it diagnosed. The repair really sorted everything out, no more slow warm-ups, fuel consumption went back to normal, and the cabin heating started working properly again. Plus, that annoying check engine light hasn't come back since. Given your mileage and symptoms are so similar to what I experienced, I'd say you're definitely on the right track suspecting the thermostat. Just make sure to get it checked soon, I learned the hard way that leaving it too long can lead to bigger issues. Have you noticed that sweet smell I mentioned? That'd be another confirmation you're dealing with the same thing I had.

Thanks for sharing that additional info – especially about the sweet smell! Come to think of it, I have noticed something similar when starting up on cold mornings. It's really reassuring to hear your repair went smoothly and fixed all those issues. I'm feeling much more confident now about what I'm dealing with. My symptoms match yours almost exactly, and the mileage being similar is quite telling too. Think I'll go ahead and book it in with my workshop next week. I'd rather get it sorted now before it potentially leads to any bigger problems like you mentioned. The occasional check engine light was making me nervous, but knowing this is likely just the thermostat is a huge relief. Really appreciate you taking the time to share your experience in such detail – it's exactly the kind of firsthand info I was hoping for. I'll probably have them check the coolant levels too while they're at it, just to be on the safe side. Thanks again for helping me figure this out!