This is your axuality water pump. Passanger side one very important!!! If its don't work it will have over heating. U have one more on radiator - driver side. It's common problem on Cateras, they quit working, or leak. I would recommend u to replace it asap.
From the book:
With the ignition ON, the heater auxiliary water pump runs continuously and increases the flow of coolant to the heater core. At low RPM or idle, coolant circulation to the heater core is low and a failure in this pump would result in poor passenger compartment heating. The pump is mounted on the RH strut tower.
Put your hand on the pump and wiggle the connector and see if it starts working. I had a bad connector and a bad pump. I got one from the junkyard for 15 or 20 dollars. If you do that, make sure you get a receipt. I had to go back a few times to get one that worked.
What do you mean to see if it starts working again? I mean my engine doesn't overheat or anything, in all the car works well, that doesn't seem to be hindering the car any. But i thought you know fix it now before something bigger happens.