Stock 05 GT 5sp, 180k miles.
I've had three moments in the last month where the temp gauge rose on me. Never went above the upper "not-red-yet" tick mark, but in 18 months of owning the car I've never had it move above operating temp before. I'm not sure what the symptoms are telling me.
First "hot" instance: Just got back to car in a parking garage after an evening dinner. A/C on, gauge goes to about 10 o'clock. A/C off, fans cooled the engine while I was waiting in line (read mostly stationary) to pay for parking. No more issues for a few weeks.
Second "hotter" instance. Driving around 35mph with A/C on. Turn A/C off, windows down. I notice once I pull into a drive through that the temp gauge was reading slightly hotter than the last time. Fans running. Cools off once I start driving again.
Today's "hottest" experience: 45 min interstate drive home in rain. Cabin was warm from having sat in the sun all day, so A/C on for a while at interstate speeds when it was raining. A/C off, windows down once rain stops for last 20 minutes of commute. Back roads with a few short lights, no stop and go traffic. I normally coast the last 1/3mile in my neighborhood in neutral. As I pull into my garage, the gauge is reading higher than the two previous times, but still below the tick mark before the red. I can hear a fan.
None of the instances were brought on by hard running.
Things I notice:
1. A/C was on during at least some part of each time. I rarely use A/C, I usually just have my sunroof open.
2. From 156k-179k I know the coolant has not been flushed. It still looks nice a pretty antifreeze green. That will likely happen with some unrelated major maintenance coming in a week or so.
3. I have had the in dash bubbling sound for quite a while. It comes and goes. Hasn't coincided with any temp rise previously
4. Coolant overflow bottle was slightly below "Low." I topped it off.
5. Turbo coolant bottle had not as much as I would have liked to see. poured rest of water in there.
6. Freakin this turbo coolant line guy
I've never smelled or seen any coolant leaks since I've owned the car (18 months and above mentioned mileage)
Any ideas if any of these symptoms are related? As I mentioned above, I have some big maintenance jobs coming up, I'd like to know if I should add another. Water pump? Thermostat? Coolant flush? Replace lines? I haven't checked the fans, at least one is running.