my car's temp starts rising when i leave it on idle for more than 5 minutes. whenever im waiting out in the parking lot or when im stuck in traffic, i see the gauge getting hotter; i have to rev up to make it cool down. I'm thinkin it's my water pump...what's the problem?

 

I think so because if your just sitting idle and the temp is going up your cooling system is not flowing properly which means either the pump is not spinning freely as it should or there is a deposit buildup somewhere thats not letting the coolant flow freely.

 

Check the thermostat. It might have died and now it's not letting the coolant circulate.

If not, try the pump.

 

i already changed the thermostat so im pretty positive it's the water pump now.

 

Foolish question first are the fans kicking on?

As far as the water pump goes -
Make sure you flush the radiator when you change out the water pump. You will be able to see if there is alot of build up in there or "crud" floating around. If there is please be sure to flush out as much as possible to clean out the build up. If there are calcium deposits in there get some coolant flush and make sure it has acid it in so it will break down those deposits. Also from experiance last weekend make sure the block is emtpy!! I took a nice antifreeze bath taking mine out!! If you have not changed the timing belt change it since you will have it off anyway.