Another issue I have is the coolant will suddenly leak out from the reservoir but it shows no signs of overheating on the gauges and I only know the coolant is gone because it will start smoking from the hood. This is the second reservoir cap and reservoir I have replaced thinking it was a faulty cap but is still does it but not all the time sometimes I can go a few days in between it coming out the reservoir.

2002 ford f150 rwd 5.4 triton sc

 

I would suspect a leaking head gasket. Maybe get a hydrocarbon test done on the coolant.