Was taking Gratiot down to the Detroit auto show and at about 9 mile road, my coolant light came on. Just did a timing belt job replaced all hoses and flanges connecting the upper radiator to the head, reservoir bottle, the hard metal coolant pipe and installed a stage 3 spec clutch. Well anyways I wasn't going to stop in that part of Detroit because it's a bad area and limped the car to the parking garage and opened the hood the coolant was still in the reservoir. I decided to leave it came back after a full tour of the auto show. I looked again and the coolant level had gone down so I opened the reservoir to fill it and there was pressure and the reservoir and it refilled. Got home and went to drop my wife off at work and checked the reservoir before even starting the car, it sat for about eight hours and did the same thing it did at the auto show. Has anyone had this happen? I'm thinking heater core issue because heating was spotty last night and this morning or some blockage in the radiator.