You will find two hoses that should be replaced. Do a search -- pictures are available. Also give a look at the hoses in and around the T body when it removed. Now is the time to replace them.

I can only assume that the coolant was evaporating -- otherwise it should have dripped on the ground. You will need replacement seal for the supercharger -- also get the seal for the supercharger plug on top. The proper way to fill the system is through that opening and the expansion tank. The small tubes beed the system. Do a search you will find the procedure.

The final instruction is to overfill the expansion tank -- the car will then expel the excess tot he overflow in the fender.

The expansion tank is just that --- It's designed to hold the coolant and maintain the proper air gap ... If it's sucking coolant back ... the valve is faulty. It's designed to hold the pressure. Both of mine will hold pressure for months.