Giulia Cooling System Mystery: Dual Temperature Troubles

Had almost the exact same issue with my 2021 Alfa Romeo Stelvio diesel last winter. As someone with some experience working on cars, I initially tried the basic checks, coolant levels, visible leaks, cooling fan operation, but the temperature fluctuations persisted. The symptoms you describe match my experience perfectly. The cooling system was struggling to maintain consistent temperature, with both overheating during normal operation and slow warm-up from cold. After monitoring the temperature sensor readings, my workshop confirmed it was indeed a faulty map thermostat. The repair cost me 350 Euro including parts and labor. The water pump was also inspected during the repair and found to be functioning correctly. Since the replacement, the engine temperature has remained stable and warm-up times are back to normal. To help diagnose your case more precisely, could you share: Current mileage on your Giulia, Whether youve noticed any check engine lights, If the temperature gauge shows consistent readings or fluctuates, Whether youve had any recent cooling system maintenance These details would help determine if youre dealing with the same issue I encountered.

Had it looked at during my last service at 71753 KM. The mechanics tested for coolant leaks and checked the water pump thoroughly. Both were fine. They confirmed my suspicion about the thermostat being the culprit, readings were inconsistent, suggesting a sticking issue. The cooling fan was cycling normally, but the thermostat wasnt regulating flow properly. Worth getting a professional diagnostic before replacing parts. The temperature fluctuations could also indicate air in the cooling system or other issues. My case turned out to be the thermostat, but best to be certain. The repair quote I received was 380 Euro for parts and labor combined. Not too bad considering its a relatively straightforward fix for the cooling system issues.

Thanks for the update on your Giulia's diagnosis. I dealt with almost identical temperature control issues on my Stelvio, and the symptoms match perfectly, inconsistent thermostat operation causing both slow warm-up and overheating problems. The price quote of 380 Euro is very reasonable and in line with what I paid (350 Euro). Since they already confirmed the water pump and checked for coolant leaks, replacing the thermostat is definitely the right call. The sticking behavior you described is exactly what I experienced, the thermostat would get stuck partially open or closed, causing those erratic temperature readings. After my thermostat replacement, the engine temperature stabilized completely. The warm-up time returned to normal, and I havent had any engine overheating issues since. Just make sure they properly bleed the coolant system after the repair to prevent any air pockets. For what its worth, the repair was relatively quick in my case, about 2-3 hours of labor. The new thermostat has been working flawlessly for over 8 months now, so its proven to be a solid fix for the cooling system problems.

It's good to get confirmation from someone who experienced similar issues. My Giulia will be going in next week for the thermostat replacement. The cooling fan seems to be working fine now, but I noticed the temperature gauge has become even more erratic over the past few days. I appreciate the insight about the repair time and bleeding the coolant system properly. The 380 Euro quote seems fair based on your experience. The mechanics assured me they would pressure test the entire cooling system after the repair to check for any coolant leaks. Will update the forum once the work is completed, but feeling confident now that the thermostat is the root cause. The symptoms match exactly what you described, inconsistent temperature control during both warm-up and normal driving. Hopefully this helps others who might encounter similar cooling system problems with their vehicles.