Infiniti G's Coolant Mystery: Radiator or Hidden Leak?

I had a similar issue with my 2011 Infiniti M37 last summer. Initially thought it was just low coolant, but the problem persisted. Took it to my trusted mechanic and they found that the wiring harness to the coolant temperature sensor was corroded and sending incorrect readings to the ECU. This was causing irregular coolant flow through the system. The fix wasn't just a simple sensor replacement. The entire wiring harness section needed replacement since corrosion had spread along the connections. Got it done at a specialized Infiniti shop since they had experience with this specific issue. It was a serious problem that could've led to engine damage if left unfixed. From your symptoms, it could be similar, especially if you're getting inconsistent temperature readings. I'd recommend getting it checked at an Infiniti specialist rather than a general mechanic. They'll know these models' common issues better. My advice: Don't wait too long on this one continuous overheating can cause bigger problems down the line.

Thanks for sharing your experience! That's actually really helpful since I've been worried about potential engine damage too. I had no idea about the wiring harness being a possible culprit. Can't remember if you mentioned it, but do you recall how much the repair set you back? Also, have you had any cooling system issues since getting it fixed?

Hey there! Happy to help with more details! Since getting the repair done, my M37 has been running like a dream no more cooling issues whatsoever. The radiator shutter is working perfectly now, which was actually a functional limitation caused by that faulty wiring harness to the sensor. As for the cost, it set me back 155€ at the Infiniti specialist shop. Money well spent though, considering how smoothly everything's working now. It's such a relief not having to worry about overheating anymore or constantly checking coolant levels. Trust me, getting it fixed by a proper Infiniti specialist was totally worth it. They knew exactly what they were looking for and fixed it right the first time. I've put thousands of kilometers on the car since then without a single cooling-related problem. Just make sure you get yours checked out soon you definitely don't want to risk any engine damage!

Thanks so much for all the detailed info! I actually took your advice and went to an Infiniti specialist yesterday. You were right about going to someone who knows these cars they found the issue pretty quickly. Turns out it wasn't the radiator shutter at all, but a cracked coolant reservoir that was causing the problems. The repair cost me about 200€, a bit more than what you paid, but they also did a full cooling system flush while they were at it. Took her for a good test drive today and no more overheating! The temperature gauge is staying steady now, and I haven't had to add any coolant. Really glad I asked here and got your advice about going to a specialist. Saved me from probably making things worse at my regular mechanic. Thanks again for helping me out definitely feeling better about the whole situation now!