Outlander,My car will be starting perfect and when the gas tank gets lower it will start having problems .

I have an 2003 Mitsubishi Outlander, my car will work perfectly but when my gas tank starts to get low the car will start having problems starting. I would have to push the gas to get the car to start running and it will run perfectly. What could be wrong with my car. Also, my car will overheat very fast we put water in it a month before and next month the water will be low or gone cause the car to run hot.

My car has 170000 miles.
My car has an automatic transmission.