I was driving my Father-in-Law's 2000 F150 the last few weeks. There is a strong smell of coolant coming through the AC vents that gets worse if I get the engine over 2000rpm or 70mph. When I stop it is dripping coolant roughly in the area where I think the heater core is located. Other than these issues the truck does not over heat but it is losing coolant and that strong smell is coming through the AC vents. It occured to me the other day that I do not hear the loud 2-4 second roar as the engine is started so I wonder if the fan clutch is bad. A bad fan clutch would not explain the strong coolant smell in the AC so what does it sound like I am dealing with here? Any suggestions would be appreciated!

 

If there is nothing visual as you look under the hood, then it's probably a bad heater core. If you do a test on the cooling system with a pressurization unit, you can more easily find/confirm some leaks.

 

Yeah, I was thinking either the heater core or fan clutch. Maybe both are bad. I cannot see the leak when looking at the engine from above and have not gotten under the truck to see where it is leaking from below.

 

Feel the carpet below the heater core.