Weird Tempetures...

I got a 94 cutlass supreme about 2 months ago and my car seems to be overheating. Earlier today, when i started my car i was driving for about 4 minutes and my tempeture was at about 200 already.. and it was still going up.. it went up to about 260, so i parked over on the side of the road and turned off my car. About 5 minutes later i turned my car back on it was at about 210, so i started it and left.. the tempeture went up to 280 and then all of a sudden it went to 200 and then started going up to 280 again? and it kept repeating (going from 280 to 200 etc.) About 3 weeks ago, if i drive slow it stayed at 200 but if i drove fast and accelerated quickly it went up to about 280 (but stayed there) .. What is the problem with my car? The heater also does not work in my car.. i turn on bi lev and it only comes out of the top.

Here is what was going on about 2 months ago..

http://www.automotiveforums.com/vbulletin/showthread.php?p=3778723#post3778723

Also, i have not changed the thermostat and Water Pump yet.

I think you answered your own question. Make absolutely sure that you get the air out of the system. There should be a bleed valve on the top of the thermostat housing if not simply leave the radiator cap off until the thermostat opens and refill. Do this several times and the air should be out of the system. Good Luck and if I didn't already welcome you, Welcome to AF!!

I do not know if your problem is solved...but this looks very much like a blown head gasket. WHen exhaust leaks through blown gasket and invades the cooling systems, all the symptoms your describe are the direct consequence.
So..do not sopend for the pump and radiator...they will not do better .