95 Aurora, strange issues, please help!

I have a 95 Aurora, it has 150,000 miles on it, always ran fine. I find myself always refilling the oil though, ever month or so, and it doesnt leak... thats not my problem though... here are my problems, i find them to be very strange.

About a week ago, I got a "low coolent" display on the computer, and noticed my temp slowly rising. Come to find out, theres no coolant in the car, strange. So i filled it 50/50 with that Orange coolant and water. However the "low coolant" display has never went away. Anyways, not a big deal, however Ive been checking the coolant day-to-day. And I noticed a puddle under my car. So i have been having to fill it like everyday. It was getting expensive to do, so i ended up just using water, just to get me around until i get the problem fixed, filling it up before my trip to work, and again for the way home. Im not sure if that is ok or not to use only water, But it leaks very fast so the water isnt in there for very long. The car would be fine on the highway, running around 215 degrees, but in traffic it would over heat. BUT! Today was different!
I went out to my car to drive to work, and the water was still full, it didnt leak out like it has been, weird. I drive it, and it didnt over heat at all, even after i got off the highway, I even let it iddle for a long time after i got to work, and it stayed at 210. However the ride home was a ride not to forget. Again, it didnt over heat, but the oil pressure dropped real fast and it stalled a couple times before i got onto the highway. I let it sit for 10 mins, turned it back on, it was fine, so i got on the highway, and everything seemed ok. After a 45 min drive on the highway, temp still ok, I got off the highway and sat in a lil traffic, and everytime i slowed down, the oil pressure would drop and my car would stall. I checked the oil level, and it was full. The pressure would be around 25 PSI, but when i would idle, it would drop like 1 per second, and when it got under 10 PSI, it would stall. I would start it up again, and the engine would automatically rev up to 3000 rpms and say up there, building the PSI up to 60. When I shifted it to drive, and started going again, same thing would happen. Finally after stalling about 20 times in a 1/4 mile span, I gave up, and parked in a parking lot, and called a cab. I drove back to the car tonight, at 9pm when there was no traffic. It would start, then right away stall, start again, and stall again. The 3rd time, i started it, i floored the gas, and built up the oil pressure to 60 PSI I drove away, oil pressure was around 30 while driving, and at a red light it stayed in the 20's, engine cold. But it never stalled. I got back home, its in my driveway, but I'm done playing with it today, and I'm gonna see what it does tomorow. Can anyone shed some light on this subject! I have no idea how it leaks one day, then its ok, then it overheats another day, then it doesnt, then it stalls another day! And now it appears to be ok, but the engine was cold. Also, The computer never does pop up "low oil pressure" so maybe stalling has nothing to do with it, i dunno. Let me know, sorry for making this so long, just wanted to give everyone a detailed problem to try and solve

try putting a gauge on the oil to see if the display is on target.
Some oil pressure sending units have a cutoff for fuel pump so that if
car is wrecked and key is on it will kill the fuel pump,reducing the risk of fire.
This is most likely whats happened to you. You may have a bad oil pressure sending unit.
dont know about your leak. did you purge all air out of system?
Have you added tablets for leak stop>
Only use GM or Bars tablets

No, i'm not sure how to take the air out, i just refilled the canister. And no I havent used any tablets, is that safe for my radiator to use those? Also how to I put a guage on the oil to make sure my computer is ok??

also, to make the story interesting, on the way to work today, my car both over heated about (250 degrees), and stalled about 12 times. On the way home, never over heated, never stalled, same driving conditions both ways. How odd is this problem! What will tomorow bring? Also, if anyone could answer this, if the tempature where I am stays between 40 degrees and 65 degrees, what is the difference between using just water and using 50/50 water, antifreese? Can I harm my car by only using water? Keep in mind, i'm having to refill it every 2 days or so.

First things first, fix your coolant leak, its probably the radiator. Regarding the rest of your problems this is a long shot, but here is an idea. Most cars with fuel pumps have a relay that turns on the fuel pump when the car is running. There is also a backup relay that engages if oil pressure is above 10 psi (or some similar presssure). Perhaps your primary fuel pump relay is broken, so that the only way your fuel pump is being engaged is with the secondary relay that only enagages with enough oil pressure. So perhaps, in theory when your car overheats your oil pressure drops just enough that the secondary relay shuts off and your car stalls. Just a thought. So I would check your primary fuel pump relay, but fix the overheating issue first...you will eventually cause some major damage to your car if you don't fix the overheating issue.

interesting theory, however sometimes the car was stalling when the the car tempature was around 210, so it wasnt over heating.... also, this morning on the ride work, and last night on the way home, everything was fine.... no over heating, no stalling? How could this problem "repair" itslelf??? lol thanx for the ideas.

Well this problem is indirectly related to overhearing. The oil pressure might get low enough in general to not engage the backup fuel pump relay. A good test to see if the primary relay is working is to get in the car with the drivers door open and turn the key to the on/run position. Do not start the car. You should hear the fuel pump turn on (humming noise) for a few seconds. If you don't hear it, either your pump is really quiet, you have poor hearing or the fuel pump relay is not turning on. If you don't hear anything I would investigate the fuel pump relay further.

interesting theory, however sometimes the car was stalling when the the car tempature was around 210, so it wasnt over heating.... also, this morning on the ride work, and last night on the way home, everything was fine.... no over heating, no stalling? How could this problem "repair" itslelf??? lol thanx for the ideas.

um - have you checked the fans? do they run when it is overheating? if you turn on your heater with the fan on high, does the temp come down?

sounds like your fans are not coming on consistantly - bad connection/relay/whatever; 'could even be a bad sendy.

215 is too high anyway; should be around 200 and up to 220 in traffic; thats about the time the fans kick on. The AC should turn on BOTH fans.

does the system hold pressure? maybe replace the cap too just to be sure and absolutely figure out where the leak is.