also leaking coolant

just purchased 99 malibu with 46,000 miles a month ago... low coolant level warning has been coming on for the last week so last night i put diluted dex cool coolant in... didn't drive it afterwards, drove it to work this morning and 5 mins after i got here coworker told me my car is leaking A LOT of coolant all down the gutter. I looked for a "fill line" last night before putting the coolant in, but did not see one so i filled it almost to the top. Am I in big trouble?

There is a possibility you just overfilled it. The excess will come out of that little rubber hose next to the cap. There is a line on the tank but I can never see the fluid in there to make use of it. it's about an inch down on the front curved part of the tank. If you don't lose any more and the light stays off, I guess you win.

be glad it leaked into the gutter - probably much cheaper than into the oil like mine did.

tlm.