how do i determine if its the water pump?

 

If its noisy/leaky.. Mainly noisy though for the symptoms you are having.. There is a plastic impellar that can deteriorate/break over time and it may not be pumping efficiantly. I dont know about the 2.8 but the 1.8t's water pump was updated with a metal impellar which comes with the timing belt/pulley/t-stat kit from ecs... I dont know if they have a 12 v kit, but if it is actually your water pump, do you know when you timing belt/tstat has been done?? I still think its just an old cooked radiator though.. If you plan on keeping the car for a long time, do the water pump and tstat and tbelt if it hasnt been done along with a radiator if its core is cracked.

 

Same thing happened to me.

1st I fixed radiator. (cracked)

Then 2 days later Water-pump went. keep in my mind if your gauge is displaying middle chances are (small chance) ur gauge is broke