I have a 2007 , 6.0. About a month ago the gauge went into the read while in line at bank , soon as the alarm went off in a matter of a minute the gauge came back to normal. when I got home the coolant tank needed pax a gallon water .... about three days later it need about another 1/2 gallon to fill it to full line ..... after driving it about 20 miles it sat in the Driveway for a few days .... I checked it again and it was full. I loosen the top of the tank and it had pressure still on it after all these days ,,,,, ( this tells me I have no leak) ..... well for three weekends in a row I drove it to the camp (350 miles) round trip with no issues. Never did check the water level in the tank during this time ,,,( I know dumb move) ...... well coming home from camp today it ran hot again. Had to add about 2 1/2 gallons of water / coolant to get it full. Ran for another 2 1/2 hrs to get home with no issues ..... get home and unscrewed cap and it had pressure and needed about 1/2 gallon in tank to refill. This truck has 145,000 miles on it. Hardly driven except during hunting season. I have a company truck for everyday driving to work etc. what are y'all thoughts. I will park it over a cardboard flat to see about a leak. Driveway is rocks. Someone said it may be blowing it out thru the tailpipe. God I hope not .....
Thanks

 

Ironically my 2007 did the exact same thing this past week took it to the dealer (only because of my extended warranty) and it needs new head gaskets. This I might add is with headstuds from when it blew them with the last owner
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Really a few different options here.....

If you have a stock EGR cooler, it could be going thru there, and burning up thru the exhaust, park the truck nose down over night pull the EGR valve and see if its wet-but I feel 2.5 gal would be noticeable thru the exhaust

The little hose that connects the EGR cooler to the oil cooler housing are prone to leaks

Or it could be the head gaskets

If it were me id make a pressure gauge for about $15 and check cooling system pressure...

Everyone assumes coolant issue means blown head gaskets...not true

 

Doesn't sound like the OP or 2nd poster are monitoring anything. Does anyone read here anymore?https://www.ford-trucks.com/forums/3...ch-folder.html