Loss of Radiator Fluid- Warped/cracked piston?
 

For some reason, over the last 4 weeks I lost about a gallon and a half of radiator fluid. I have a brand new radiator, new hoses, and 4 yr old water pump.

I filled the radiator fluid back up and the level has sustained over the past 2 days. I'm not sure if I just didn't put the radiator cap(1 year old cap) on tight enough the last time I checked the water. If this was caused by a warped/cracked piston how long would it take to loose the fluid again?

Any other problems besides? Hard to lose that much coolant just like that. Not sure about a "warped" piston but a cracked piston would give you a lot more trouble than just a coolant loss. I'd fill the system well, make sure there are no bubbles, and keep an eye on it.

So far the level has sustained. Like you said, it is a lot of coolant loss so I'm very paranoid about it now. I had the heater on tonight and I smelled a faint smell of coolant, don't know if it's normal.

if you're smelling coolant on the inside, your heater core is where you're losing it. it's probably coming out the a/c condensation drain and possibly hitting the exhaust (probably why you're not seeing alot of coolant on the ground)

Well, there's really not too many places coolant can go. Assuming you aren't leaving tasty puddles on the ground for neighborhood stray dogs and cats, it has to be either flooding the passenger side floor boards from a bad heater core, entering the combustion chamber and being exiting the tail pipe in a white plume or entering the crank case and turning your oil into chocolate milk shake. The fact that you recently had the cooling system open would point me to the conclusion the system had an air lock in it and required additional coolant. However, in these forums, what isn't mentioned is often more important than that which is. For instance, what led to installing a new radiator? If the car overheated significantly, you can start pricing cylinder heads.