Overheating

I have a 1991 Ford Probe, 4cyl, with roughly
250,000 on it. The temperature gauge gradually
goes beyond the red (260 degrees) zone, and
before, the Check Engine light would come on
when it hit the red mark. We noticed that the cap
wasn't pressurizing. We replaced the thermostat
(which was still bad) about a month ago, and
discovered that the A/C Condenser Fan was not
working, and the relay was in bad shape. We got a
new relay and tested the fan, which still isn't
working, but the Check Engine light stopped
coming on when we tested it. Just yesterday, we
decided to take it around the block to test it and
see if the fan would come on while in action, and it
still gradually climbed up to the hot mark, but the
light didn't come on, until after we had gotten it
back home. When I parked it, I heard that bubbling
noise, as well as steam coming from the
passenger side of the hood, where my reservoir is.
My question is this; could my issue be that cap not
pressurizing? Or could it possibly be my water
pump or just a bad A/C Condenser Fan? Thoughts?