I work approx 30 minutes away from home. when i got home tonight, i noticed a hissing sound coming from under the hood and a thin smoke coming out of the front grill. the vehicle is a 2001 ford f-150 with 5.4L. I investigated further based on the smell and checked the coolant reservoir, upon opening it safely, pressure was relieved and the hissing sound stopped and i found it was empty. i added water, drove shortly down the block and got a gallon of 50/50 coolant and proceeded to fill the overflow. almost all of it went straight into the radiator, mind you the temp gauge never showed a sign of concern on the way home. after doing so i drove back down to the block to my home and when i got home the hissing sound was occurring again and when i went to lift the hood, i noticed it was wet with steam. i then heard dripping and checked underneath and it was a constant excessive drip of water like someone dumped a cup of water on the top of the motor excessive. its dark outside so i cannot see if its coolant yet but with the flashlight on my phone i did notice the green coolant color on top of the motor which im suspecting is the cause of the smell. will not be driving it as i don't want to blow the head gasket as im hoping its just a coolant leak. any ideas?
Seeing as the steam is coming out of the front grille, then you likely have a hole in your coolant radiator. It is also possible, but less likely that it is a hose that goes to the radiator.
I agree, you shouldn't drive the car in that condition, engine damage is likely. Sometimes the temperature gauge doesn't work correctly if the coolant is low, since the sensor is not submerged in the water.
It is usually a relatively easy job to replace the radiator and you can also get them re-cored which makes them like new, rather than having to buy a new one.