Could be a number of things. Common issue is the inlet manifold gasket leaking. Replace those with the aluminum ones and your good. No real way to check either besides taking manifold off.
This next photo shows the hose that connects the coolant fill point to the radiator, it is very loose and slips off with minimal effort from the radiator.
What's the trans dipstick fluid look like? If it's the same colour, the trans cooler (which is located inside the radiator) has split....You will require a new radiator and have the trans flushed out properly and hope the water hasn't wrecked the bands inside the trans...