M Diesel Overheating? PTC Heater Could Be Your Culprit

Hey there! I've got some experience with cars and had a similar issue with my 2009 Infiniti G37 Diesel last winter. The symptoms you're describing sound exactly like what I went through. Took it to my regular workshop and they diagnosed a faulty electric auxiliary heater. Getting it replaced set me back about 350€, but it fixed all those issues the warning light, overheating, and coolant problems disappeared completely. The repair took about half a day. What's your exact engine size and mileage? That could help me give you more specific advice since different variants might have slightly different setups. Also, are you noticing any issues with cabin heating, particularly during cold starts? BTW, if you're interested, the Infiniti FX from those years had similar heating systems, so the fix should be pretty similar if that's what it turns out to be.

Thanks for your detailed response! My mileage is at 235,151 KM and I just had my service last month. The cabin heating actually seems fine during cold starts, it's just these other issues that keep popping up. Since you mentioned your repair experience, did you notice any warning signs before the heater completely failed? I'm trying to figure out if I should get it checked right away or if I can drive it for a bit longer.

Hey again! Great to hear back from you. Yeah, I can definitely help with that since I went through something really similar with my G37. Looking back, there were actually a few warning signs before my heater completely gave up. First, I noticed the coolant level dropping more frequently than usual I was topping it up every couple of weeks, which definitely wasn't normal. The warning light would come on intermittently at first, especially during longer drives. But here's the thing I made the mistake of driving it longer than I should have, and that almost led to more serious engine issues. Since your mileage (235,151 KM) is pretty close to what mine was when I had the problem (around 240,000 KM), I'd strongly recommend getting it checked out ASAP. While my cabin heating was completely shot when my PTC heater failed, yours being okay doesn't necessarily mean you're in the clear. These things can deteriorate pretty quickly. Trust me on this one don't wait like I did. I learned the hard way that prevention is way cheaper than cure with these Infinitis. Plus, the last thing you want is to end up stranded somewhere with an overheated engine. Better safe than sorry, right? Let me know what you decide to do. I'm curious to hear if it turns out to be the same issue as mine!

Thanks so much for sharing your experience! You've definitely convinced me not to take any chances. I'll call my mechanic first thing tomorrow morning to get it checked out. Really don't want to risk any major engine damage, especially after what you went through. The similarity in mileage between our cars is pretty striking too seems like this might be a common issue around this point. I'll update you once I get it looked at. Really appreciate all the detailed advice you might've just saved me from a much bigger headache down the road!