BMW 1 Series Heating Issues, Bypass Valve Problems?

Hi there! I have some experience working on cars and had a similar issue with my 2012 BMW 3 series diesel (the bigger of your 1 series). The symptoms you described sound exactly like what I went through. Turned out, my car had a previous repair where they replaced the thermostat, but they didn't properly bleed the cooling system. This caused air pockets, leading to overheating and poor cabin heating. The best part? The fix didn't cost me anything since it was a consequential error from the previous repair. The workshop had to properly bleed the cooling system and check the bypass valve, took them about an hour. They also updated some software related to the cooling system management. Could you share what error code you're getting? Also, have you had any recent work done on the cooling system? This info would help narrow things down better.

Thanks! My car's at 136771 KM, and the last service was about 3 months ago. They actually did some cooling system work back then. I just checked my service records, and they replaced the thermostat too. Sounds like I might be dealing with the same air pocket issue you had. I'll definitely mention this to my mechanic. Kind of relieved it might not be something more serious. I've got the error code P0128 stored, should've mentioned that earlier. Really appreciate you sharing your experience, helps a lot when you know someone's dealt with the same problem!

Hey there again! Yes, that P0128 code (coolant temperature below thermostat regulating temperature) and your mileage details definitely confirm what I suspected. When I read about the recent thermostat replacement, I was nodding my head, it's exactly what happened with my BMW! The P0128 code is pretty much a dead giveaway. In my case, I kept the service records too, and when I showed them to the workshop, they immediately knew what was up. They found air pockets in several spots in the cooling system, just like I mentioned before. Quick tip from my experience, make sure they use the proper BMW bleeding procedure. When they did mine, they had to use a special tool to get all the air out. It's not just a simple top-up-and-go job. My mechanic explained that BMWs are particularly sensitive to air in the cooling system, and that's why the proper bleeding procedure is super important. Since you've got the same symptoms and recent repair history as I had, I'd bet good money you're dealing with the same issue. Take it back to whoever did the thermostat replacement, they should sort this out under warranty since it's clearly related to the previous work. Let me know how it goes, curious to hear if it's the same fix as mine!

Thanks a lot for all the detailed info! You're absolutely right about taking it back to the same workshop, I just called them and explained everything, including what you shared about the proper bleeding procedure. They acknowledged it could be related to the previous thermostat work and agreed to check it under warranty. Got an appointment for tomorrow morning. The mechanic mentioned they'll use their specialized bleeding tool, just like you said. It's such a relief knowing it's likely just air pockets and not something more expensive or complicated. Really helpful to know about BMWs being sensitive to air in the cooling system too, explains why my previous basic top-ups didn't solve the problem. I'll definitely update you once it's sorted. Thanks again for taking the time to share your experience, saved me a lot of worry and probably some money too! Sometimes it's just great to hear from someone who's been through the same thing and got it fixed.