Had a friend look @ my car with me.  It was running a little rough and was leaking coolant.  The coolant light had been off and on for a few weeks.  When I took the car in for an oil change, the technician said that the water level was okay and that it was probably just a sensor error.  Anyway, when I opened the cap, there was no water in the resevoir.  I put a gallon of water in, and the sensor light went off. I drove with the A/C off and the windows down.  Almost cyclical, the engine seemed to be running rough and the belt would squeal.  I stopped several times to check the water leverl.  The temp gauge inside never rose past the normal.  The water level was fine each time I checked.  It no longer seemed to be leaking.  If so, no where near as much.  When I got home, I flushed the radiator.  I did not drain the block.  I cranked the car, turned the heater on high, and let it get to normal running temp. My friend said that since the water in the resevoir tank didn't ever get hot, that the thermostat was bad.  I know only the basics of car care.  I do not have the money to take this car to the shop.  Any ideas on this?

Thermostat replacement is fairly easy and inexpensive if you can do it yourself, usually under $10.00.  You will need tools and ability to follow directions that come with thermostat.  Usually there an "up" side to the thermostat and an arrow on the thermostat that must face front of car. Do not try to reuse the old gasket.  Make sure you get a new gasket with the thermostat or buy a new one if not included.

 What concerns me in your note is the belt squeal. Many times a leaking water seal on the car water pump shaft will allow water to get onto the belt surface either directly or thru wind whip in the engine compartment while driving. This causes the belt squeal when you accelerate the engine. (asuming the belt is at the correct tightness to begin with) There is no cure for this, you will need to replace the water pump. Rebuilt water pumps are availble at most car strores and will save you money. Not a job for a beginner.