Here's a recap of today's experiences: When I started my car, it took some time until the car was warmed up and the fan turned on. I revved the car a little to speed up the warming process, but it turns out my butterfly was getting stuck. The car began to rev up to 2-3k RPM. I manually adjusted the butterfly and drove without accelerating at all (because the idle RPM was 1500 for the last few days and 800 on AC). Ever since I automated the fan, I keep a close eye on the temp gauge.
While driving today, 3-5 kilometers away from my home (the car was still revving significantly), my eye caught some steam billowing out from between the fender and hood. I immediately looked over at the gauge, which showed the temperature needle a little bit above the middle (beginning to cover the temperature sign). I had my father pull over immediately. I had checked the oil and coolant levels last night and found the coolant reservoir to be low on water (between the full and low lines). I told myself I will add water to it tomorrow morning, but I forgot.
So for the first time in ages, I used a 2-liter bottle of water to fill the coolant reservoir a little more than the full mark. the water was on low now, and last night the water had been in the middle. On the way to Tariq Road from Lalqila, the revs were going so high that the only way to control them was to either turn on the AC or let go of the clutch, which we couldn't do in stop-and-go traffic. At one point, where the traffic cleared out, the car was in 3rd gear and was accelerating on its own, practically driving itself. When we got to the mechanic, the car was dead slow because of the small streets and tight spaces , and RPMs were at 3500-4000. I caught sight of steam again and saw the needle, which was halfway between the operating temperature and the red section on the temperature gauge. I had my dad immediately shut off the car and pushed it the rest of the way. We opened the hood to find out that the water in the reservoir had been boiling and most of it had been spewn out from the overflow hose.
After getting a new ("Genven") butterfly for 7000 and a carb service we were on our way. The guy waited and confirmed that the fan was turning on and sent us on our way. I was impressed by how well the car was running and how great it now sounded. But i also kept a close eye on the temp which stayed in the middle the whole time and we made our way from tariq road to lalukhet, then gulshan and then karsaz. Without any further incident.
So my question is; Did my car overheat because of this butterfly issue or is there another underlying problem in the cooling system, because of the past 2 weeks of having the fan autos there have been no issues.
Why did the water boil in the coolant reservoir and why was most of the water thrown out through the overflow pipe?
(Also what damage has been done to my car from the car temp going above midpoint)