BMW 8 Series Diesel, Thermostat Causing Heat Issues?

Hey there! I've got some experience with cars, mainly doing basic maintenance and dealing with cooling issues. I had a very similar problem with my 2021 BMW 7 Series diesel last year. The symptoms were exactly like yours, weird temperature fluctuations, slow warm-up, and that annoying check engine light. Took it to my trusted workshop and they diagnosed a faulty map thermostat. The whole repair, including parts and labor, set me back about 350 Euro. They had it fixed within a day, and the difference was like night and day, proper heating, normal fuel consumption, and no more temperature issues. Before I can share more specific details, what's your exact engine variant? Also, how many miles/kilometers have you put on the car? This info would help me tell you if your case matches what I experienced with my 7 Series. Pro tip: Don't wait too long to get it checked. These cooling issues can get worse pretty quickly if left unattended.

Thanks for your detailed input! My BMW has 57488 KM on the clock and had its last service about 3 months ago. Based on what you're describing, it does sound quite similar to my situation. Interesting that your 7 Series had the same symptoms. The map thermostat issue makes a lot of sense given the inconsistent temperatures I'm experiencing. That repair cost sounds reasonable, and it's good to know it can be sorted within a day. Think I'll get it booked in next week to avoid any potential damage. The fuel consumption increase is really starting to hit my wallet!

Hey again! Yeah, after hearing your mileage, I'm even more convinced it's the same issue I had with my 7 Series. Mine was actually around 55,000 KM when these problems started showing up, pretty close to where you're at now. Just to give you a heads up, when they fixed mine, they found that the map thermostat had basically worn out. These things aren't really designed to last forever, and the diesel engines can be pretty demanding on them. The mechanic mentioned it's becoming a more common issue with these newer BMWs. The increased fuel consumption was driving me nuts too! After the repair, I saw about a 15% improvement in fuel economy, which basically meant the repair paid for itself within a few months. Plus, the cabin heating went back to working like a charm, no more freezing morning drives! One thing I'd recommend, make sure they do a full cooling system check while they're at it. In my case, they also found a slightly loose hose clamp that could've caused problems down the line. Better to catch these things early, right? Let me know how it goes when you get it sorted. Always curious to hear if others have the same experience I did with these BMW cooling systems.

Thanks for the follow up! Super helpful to hear about the similar mileage when your issues started. That definitely helps confirm my suspicions about the thermostat. I'll make sure to ask them to do that full cooling system check you mentioned, totally makes sense to check everything while they're in there. Really good to know about the fuel consumption improvement too. I've been spending way too much on fuel lately, so if I can get similar savings, that'll help offset the repair costs. And honestly, I'm just looking forward to having proper cabin heating again. These cold morning drives have been pretty miserable! I'll definitely book it in next week and will shoot you a message once it's done to let you know how it went. Thanks again for all the detailed info, it's made me feel much more confident about what to expect with the repair. Fingers crossed it'll be a straightforward fix like yours was!

Hello. I'm getting several critical engine problems reported for my BMW 4 Series Convertible 428i. But the car doesn't feel any different, and there are no warning lights on. Some of these problems are: thermostat with characteristic field line interruption; valvetronic servomotor excitation line interruption; power supply control, among others. This car does not have the original battery, and the screen and taillights have been changed, in case it has something to do with it. What should I do? Is it worrying?

(Translated from Spanish)

Start by checking the battery connections and ensuring they are secure and free of corrosion, as electrical issues can often stem from poor connections. Since the car has a non-original battery, verify that it is the correct type and properly installed. If the issues persist, it would be wise to have a professional mechanic inspect the vehicle, as electrical problems can lead to more serious issues if not addressed. Let me know how it goes or if you have any other questions!