BMW 3 Hybrid Cooling Issues: Bad Thermostat Warning

Hey there! I've got some experience working on cars as a hobby mechanic. I had a similar issue with my 2013 BMW 5 Hybrid (had a look at the X5 too back then). The symptoms you're describing sound exactly like what I dealt with. Mine had a defective map thermostat that needed replacement. Got it fixed at my regular workshop and the whole thing, including parts and labor, cost me around 350 Euro. The tricky part with these thermostats is they can act up in weird ways, sometimes causing overheating, other times preventing proper warm-up. The increased fuel consumption and slow cabin heating are classic signs too. What's your mileage? Also, have you noticed any coolant leaks or sweet smells from the engine bay? This info would help me share more specific details about what to look out for.

Thanks for the response! My car's at 192436 KM and had its last service about 2 months ago. I haven't noticed any coolant leaks, but now that you mention it, there is a slight sweet smell when I park after a longer drive. Your experience with the map thermostat sounds spot-on with what I'm dealing with. 350 Euro seems reasonable, I was worried it might be something more serious. Did you have to wait long for the parts to arrive? Think I'll get it checked out at my regular workshop this week. Really appreciate the detailed insight!

Hey again! Thanks for the follow-up info. Yeah, that sweet smell combined with your mileage reading definitely reinforces my initial thought about the map thermostat. My BMW had around 180000 KM when I had the same issue, so we're in the same ballpark. For the parts, I had to wait about 3-4 days, but that was because my workshop had good connections with suppliers. Might take a bit longer depending on your workshop's network. Just a heads up, make sure they check the entire cooling system while they're at it. When I had mine fixed, they found a slightly worn water pump that could've caused problems down the line. Got that replaced too for peace of mind. The sweet smell you mentioned, that's exactly what I experienced. It's typically coolant vapor escaping when the system's under pressure. After the thermostat replacement, that smell completely disappeared, and my fuel consumption went back to normal within a tank or two. Let me know how it goes at the workshop. They might find something different, but based on what you're describing, I'd put money on the thermostat being the culprit. Good luck with the repair!

Thanks so much for all the detailed information and follow-up! Just got back from booking an appointment with my workshop for next Tuesday. They seemed to agree that the map thermostat is likely the issue, especially after I mentioned the sweet smell and the symptoms you described. They actually have the part in stock, which is a nice surprise. Said they'll do a full cooling system check while they're at it, like you suggested. Really glad you mentioned the water pump thing, I asked them about that too, and they'll inspect it during the service. It's such a relief knowing this is likely a straightforward fix and not something more serious. Really appreciate you taking the time to share your experience, it helped me feel much more confident about what I'm dealing with. I'll probably update once it's all sorted, but thanks again for all the help!