coolant loss

With the engine cold, remove the radiator cap and start the car. Watch for bubbles to appear in the coolant, particularly after the thermostat opens. If you see them, it's the head gasket. You may also be able to smell antifreeze in the exhaust.

Gary

Is it going in the puke tank then not sucking back when it cools because the cap isn't sealing? If you think it's a head gasket, pull the plugs. the plug in the offending hole will be washed shiny clean.

Look closely at the side of the block below the water pump. It probably just leaks cold and not enough to drip very noticeably on the ground. When they leak very slowly the coolant runs along the oil pan gasket and drips from the bell housing. It self seals when warm and driving evaporates the small amount of coolant as you drive. There will be a crystalline residue on the motor below the pump and perhaps a line of dried coolant on the bottom of the hood from the fine spray coming off the fan blades.

Bob