I have a 1998 Cavalier and I have been experiencing some strange problems with this car since March. At one point the temperature hand would go all the way over to the H and I was taught in drivers ed to cut the heater on and it will help bring the needle back to the middle and so far it has worked. I took it to my mechanic and they did a diagnostic test and said they could not find nothing wrong with it at first, then said I needed a new thermostat which was a relief because they are so affordable. For the last 3-4 weeks it has been leaking antifreeze and trying to run hot. The hand has been going almost past the H for example Christmas day in which I was on my way to my family's house(in town) had to stop at Walgreens to pick up antifreeze. I had my brother put in the antifreeze and a week later all the antifreeze was gone, put some more in last Wednesday by Friday it was all over the ground as if I poured it.A friend of the family that has worked on my brakes and put my alternator was going my car out for me. He said when he first cranked it up the hand had went straight over to the H, and that day it was cold and the car had been sitting for 3 hours. Before I made it to my mother's house I had put antifreeze in it and not even 5 minutes in the car the hand went over to the H and the when I turned on the heater it would not bring it down for nothing except at a red light. The man that checked it out filled it up with water and drove it for 15 minutes and then let it run in the driveway for 30 minutes and it never ran hot( that was this past Friday). It held all the water and did not leak Friday or Saturday, Monday the water was gone and I had to fill it back up before I ran an errand and before I went to return home. I put a new water pump on 3 years ago and I have had the radiator checked and their hoses and everyone says they are fine. Also my A/C went out in October, what is going on I am in college and cannot handle a car note right now can you please help.