Hello,
New member here, I'm at a loss so if I'm breaking rules let me know. I'm 69 years old vet and I find my patience wear thin quickly now and sometime can annoy my wife. I'm still a car guy and I just let my 1992 Mustang coupe go for a 2001 F150 Lightning with 86,700 miles. I hope there is a simply answer to my question; The truck over heated, as soon as the dash light came on I pulled over a shut if off. After it cooled I went to wakmart and put a gallon of 50/50 antifreeze in it, but it needed another gallon of water to show in the plastic bottle. I drove it more that day watching the gage and it was good, The next morning I checked and the bottle was empty. I added more to show in the bottle. I had it pressure tested and it held pressure so I replaced the radiator cap, which in this case is the plastic bottle cap. I drove it home after the check, about 15 miles and parked it. This morning I checked and the plastic bottle is empty. ???????? Where is the water going if it holds pressure with the tester????? Help, Thanks, Jim5108

 

Sorry, Jim5108 again, I forgot to mention, there isn't any oil showing on the oil dipstick, it looks clean. Thanks

 

Not sure if you figured out out yet but there are two different cooling systems on these one for engine cooling and one for the intercooler to cool the charge air

If your adding to the engine cooling system constantly it is either burning or leaking somewhere

If it is the intercooler system you might have an internal leak had that happen to mine took the intercooler out and had a radiator shop seal it up

Good luck