I drive a 1997 Cadillac SLS. For the past couple of days I've been getting the "Check Coolant Level" and "Check Oil Level" error messages as soon as I start my car. In the past I've been able to get by for a couple days with no problems. I came back home from school last night and once I got off the interstate I had a message saying "Check Coolant Level" and then "Engine Coolant Hot...Idle Engine...Stop Engine Now". I put in 50/50 silicate-free coolant in and it over heated again this afternoon on my way home from an oil change. I ended up adding the remainder of the coolant, roughly 4 liters in all. I had a radiator flush done in December, and I know for a fact that my car is not leaking any fluids of any kind (I park in the same place daily). I'm thinking that maybe the problem is that I added the coolant while the engine was still very hot, and I was told that coolant needs time to actually take to the vehicle when added before it does its job (not really sure about that last little piece of advice). I'm thinking about taking the car to get the coolant system looked at tomorrow, but I'd rather find out it's a small problem and take care of it before paying $100 for what could have been a quick fix.There's no steam or hissing of any kind, and my owner's manual says that is a sign that it's not a very serious issue.
