If really on top then probably the intake manifold gasket ,study it closely .
Look for a leaking hose, water pump, or raditor find the leak and fix it.
They fixed the replaced the raditor and it still leaks in front of the vehicle.
there are might water jackets there lie some fords replace the gasket
Stop leak is a temporary fix. I don't recommend it. Tighten the clamps on the hoses going into the raditor.
Follow the upper raditor hose from the raditor to the motor, the raditor hose is connected to the thermostat housing, take the houseing off, the thermostat is under the housing.
there is a hole in the back of your engine under the exaust manifold. pour water in the raditor. if you get under the car you can see water comming out put it in the whole and hit with a hammer till flush with the engine
u didnt mention what size engine..either way just follow the upper raditor hose from the raditor
my 97, 318ti did the same thing, replaced every thing, spent 3 weeks tring to solve problem. new raditor but used my old cap. my old cap didnt hold the pressure needed. bought new $15 cap. so for now the raditor cap was the problem. now i have to solve the problem with my drivers side window comming off track.
Follow the upper raditor hose from the raditor to the top of the engine.Where the upper rad hose ends on the engine is where the thermostat is.
The thermostat is going to be located in the raditor. Use extreme caution when taking the raditor cap off to advoid burns from boiling antifreeze. Once the raditor cap is taken off you shuld see the thermostat. Just pull out to remove, or push hard to install.
head gaskets they all do it i have two 99 sts with the same problem cost about 2500 to fix correctly.
bottom of rad you will see a small drain valve