BMW XM Cooling System Issues, Thermostat Problems?

I have some experience working on BMWs and actually faced almost identical issues with my 2021 BMW X6 M last winter. It was super frustrating, especially during cold mornings. After dealing with similar symptoms (slow warm-up, poor fuel consumption, inconsistent cabin heat), I took it to my trusted workshop. They diagnosed it as a faulty map thermostat, just as you suspected. The replacement job took about 3 hours, and I ended up paying around 350 Euro for parts and labor. Since then, everything's been running smoothly. I also own a BMW X5, and these cooling system components are pretty similar across their performance models. Just to help you better, could you share: How many miles are on your XM? When did you first notice these symptoms? Are you getting any specific error codes with that check engine light? Feel free to ask more questions. With some details, I might be able to offer more specific advice.

Hi! Thanks for sharing your experience! My XM just hit 88,353 KM and had its latest service about two months ago. I started noticing these issues about three weeks back, right after a particularly cold morning. The check engine light usually comes with code P0128 (coolant thermostat rationality), which definitely backs up the thermostat theory. The symptoms you described with your X6 M sound exactly like what I'm experiencing. That repair cost actually sounds more reasonable than I expected. Did you use OEM parts for the replacement? I'm thinking of getting it fixed next week, just want to make sure I'm prepared for what's ahead. Really appreciate the help!

Hi! Thanks for those details! Yes, my mechanic used OEM parts for my X6 M, wouldn't risk anything else on these high-performance engines. The P0128 code is exactly what I got too, so I'm even more confident now that we're dealing with the same issue. Just a heads up from my experience, when they replaced my thermostat, they also recommended flushing the entire cooling system while they were at it. I agreed, and I'm glad I did because they found some debris that could've caused problems later. It added about 100 Euro to the bill but was worth the peace of mind. After the repair, the difference was night and day. The engine now warms up properly in about 5-7 minutes, fuel consumption improved by about 15%, and the cabin heats up much quicker. Haven't seen that check engine light since! One thing I'd suggest, get them to check the water pump while they're in there. These BMWs sometimes have the pump go bad shortly after thermostat issues. Mine was fine, but it's worth checking since they'll already be working in that area. Let me know how it goes after the repair!

Thanks, That's really helpful advice about the cooling system flush and water pump check, definitely going to request both when I take it in. Better to be thorough and prevent future headaches! The potential 15% improvement in fuel consumption sounds great too, as these recent issues have been making me wince every time I fill up. I'll make sure to insist on OEM parts. With what I paid for this XM, cutting corners on repairs doesn't make any sense. I've already called my mechanic and booked it in for next Tuesday morning. They quoted me similar prices to what you mentioned, so I'm feeling more confident about the whole situation now. I'll update you on how it goes after the repair. Really appreciate you taking the time to share your experience, it's been super helpful in understanding what I'm dealing with. Thanks again!