I had the ECM and Crank Sensor replaced on my 88 Cavalier and when I went to pick the car up, (it had run for about 5 min) I noticed a leak as I was pulling out of the parking spot. When I opened the hood, the coolant overflow was right up to the top. When I took it in, it was just below the cold fill line. When I remove the cap on the overflow the leak stops; it start again when I return the cap.

The mechanic came out to look at it, and said it was the head gasket. Just before I took it in, I had noticed an antifreeze leak to the left and below the thermostat, but not from the thermostat. The car runs smooth now and there have been no other warning symptoms. Any chance the car will run for awhile? How about those leak stop products, are they worth a shot?