Hi, I my car has 150000 miles and it started overheating and losing cooler. I took it to the mecanic and they checked the termostat, the radiator for leaks and circulation. He also changed the gasket tha seals the top of the head of the engine. I used it for 3 weeks in the city and it worked fine, the temperature indicator never passed the middle even after one or 2 hours of use.
The problem came back when I took a 3 hour drive on the highway, at the end of the drive the indicator was very close to the red area and I had to refill the radiator and tank with half of galon of water (I did not had cooler so I used water).
I was thinking that may be the cooler got lost during the 3 week for us in the city but when I drove back that same day the indicator started getting close to the red area when I was going up hill at about 55mph, this hill took about 15 min and ahead is a down hill that takes another 15 min, after that is a light that take about 5 min to cross and the indicator was all the way up again despites the 15 min of down hill.
Any suggestions? (buying a new car does not apply ;)
Thanks for your time reading this.

Well I'm by no means anywhere close to a mechanic so I don't know what else to say besides that the next time your engine starts to overheat, turn on the heat full blast. Just be sure to roll your windows down. It is not a cure but will help until you can get to a gas station or what have you. It really does work. I have had to do it a few times myself.

How many times did the vehicle overheat before you had someone look at it? When you say they replaced a gasket, are you referring to the head gasket? If that is the gasket they replaced, did they resurface and presssure-test the cylinder head before putting it back together? It's very possible that you overheated the car so badly that you warped the cylinder head; if it wasn't resurfaced then replacing just the gasket isn't going to solve your problem.