Engine was rebuilt within last 500 miles.

Car has been running great but I noticed a drip of coolant on the garage floor last week. I checked the radiator and it was full. The reservoir was empty, though.

I got the car up to temperature, let the fan cycle, then put the car on the lift and left it running. There were no visible leaks underneath.

I then opened the airbox and there was green coolant in there and all the way down the snorkle (icebox intake). The weird thing is that this coolant was green, and the coolant I'm using is blue. So I cleaned it up, drove the car again, and checked the airbox. It was bone dry. The intake arm was dry, so I am thinking I sucked coolant up, but I guess it's possible that it dripped from the TB.

Everything seemed fine at this point so I assumed I just didn't add enough coolant when I did the swap and it bled itself a little more, so I filled the reservoir back up and drove it again. Car ran great, didn't smell like it was burning coolant, didn't overheat. No bubbling in the coolant and the oil looks brand new.

I checked the coolant level this morning. Radiator is still full but the reservoir is empty again.

I'm thinking head gasket or heater core. But I don't have any signs of either besides losing coolant from the reservoir. It does blow thin white smoke on startup but that goes away after the idle settles. I figured that was just extra fuel but now I'm not so sure. The only reason im thinking it could be the heater core is because these problems only started when I began using the heat (at least as far as I noticed). Everything was fine until then. But the windows aren't fogging up and there's no wet spots on the floorboards.

Curious if anyone has any tips to diagnose further or has an opinion of what it could be

I'm thinking of maybe throwing some UV dye in the radiator and then checking the oil with a blacklight?

 

I think it's solved. Ran a cooling system pressure test and found two leaking hoses. Tightened those up so we will see if I keep losing coolant.