Loosing coolant

Losing coolant and steaming, although gauge never registers hot or even normal operating range however it does move slightly. I still have heat through my vents. After parking, I can clearly see where coolant has sprayed inside the hood and it begins to leak somewhat onto the ground but does not drain more then a half liter of water. Oil cap shows no sign of a head gasket issue, fans appear to be working. So my question is this last summer some jerk stole my catalytic converter. At the time I could not afford to buy a new one so just welded a straight pipe. Could that have an effect with my loss of coolant? Because even on short trips once stopped I can visibly see steam coming from my hood. I have replaced the cap twice once with a pressure release and standard cheap that is one there now. I also purchased a new radiator last year. I am at a loss.