I have been fighting my F250 all spring/summer. I've been through two mechanics and a list of repairs including: -radiator cap (2+) -thermostat (at least 3... just to be sure) -fan clutch -water pump -radiator checked at radiator shop -head gasket (ouch) We finally got the truck back from the shop yesterday after getting the head gasket replaced and the heads completely rebuilt. I was relieved to finally have the problems behind us. Today we had our 40 miles away route to give it a true test. On the way there myself and coworker both thought it looked like the temp gauge was creepin up, and sure enough on the way home it boiled all the coolant out of the radiator cap. Luckily our mechanic had another of our trucks that he just finished in, so we towed the mowing setup and the F250 home with that. The truck never overheats in town, and never on the highway unless pulling the trailer. However sometimes only 2 or 3 miles of highway driving while pulling the trailer causes it to overheat, other times we can go 10 miles before it acts up. In the case today we drove around in town all morning, then 40 miles to wichita, then probably 15 miles mowing in Wichita. We made it 5 to 10 miles from our last stop before it overheated again. I am at the end of my rope with this truck. I don't know what to do. The truck is probably only worth $6,000 or so in running condition, and I've put at least $4500 in it so far to fix this issue. I am hoping the mechanic will cost share the head gasket repair since they misdiagnosed it. Just on a hunch I am going to replace the coolant reservoir with one that's OEM. I put a new reservoir on last summer due to the old one leaking, and my theory is that the radiator caps aren't fitting correctly on the aftermarket tank and causing too much or too little pressure. What's next?