Recently replaced my water pump and thermostat housing. Need to replace the throttle body gasket but waiting on part.

my question is :
there is coolant leaking on the passenger side under the Fuse Box. What could it be from ?

 

what your year and model? welcome to the forum. moved your thread to the 5th gen general section where it will hopefully be answered.

 

I don't know 5th gen cars but that's a typical spot in many cars fo a heater core to leak.
Hope not because that's usually an expensive repair because it's so labor intensive.