Hello fellow car enthusiasts, I've been grappling with a rather vexing automotive issue for approximately six weeks now, and I'm turning to this forum in search of some much-needed advice and expertise. The problem initially manifested itself as the dreaded red coolant temperature warning light flickering to life while I was cruising along the freeway. Interestingly, I discovered that turning off the air conditioning during freeway driving (at speeds of 60-70mph) would typically extinguish the warning light after a couple of minutes. There were a few instances where I failed to notice the warning light and didn't deactivate the AC, which subsequently triggered the check engine light. Fortunately, the check engine light tended to disappear after a day or so, as long as I managed to avoid triggering the coolant temperature warning light. Upon closer inspection, I noticed dried coolant residue along the passenger side of my vehicle, and the coolant reservoir appeared to be consistently low on coolant. My initial response was to top up the coolant reservoir, and this seemed to alleviate the issue for about a week. However, the problem resurfaced, with the warning light recurring, followed by coolant spraying out of the reservoir. In an attempt to remedy the situation, I experimented with running the car in maintenance mode, raising the coolant reservoir and leaving the cap off to expel any trapped air, suspecting vapor lock as the culprit. Nevertheless, I'm still grappling with the issue, albeit in a somewhat different manner. Then, I stumbled upon this video () and decided to give it a try. Remarkably, it appears to have resolved the problem, at least for the time being. Here are my questions: 1. Could there be any potential drawbacks or side effects associated with the YouTube-suggested fix, which involves removing the O-ring from the coolant reservoir cap? 2. I've noticed a small hole at the back of the reservoir cap housing, which seemed like it might have been intended for a hose at some point. It acts as a funnel when refilling coolant, preventing leaks. Should this hole be there, or am I overlooking something? I'm considering sharing a picture for reference. 3. I'm open to any additional advice or suggestions you may have to offer regarding this puzzling issue. Your insights would be greatly appreciated. Thank you in advance for your assistance, and I look forward to your input on this matter.