Use a pipe cleaner or a piece of wire to knock scale and dirt from the water pump weep hole.
1st and 2nd generation (every 12000 miles):
1: From above and just in front of the alternator pulley, look down to the water pump.
2: The weep hole is at about the 7:00 position, below and to the left of the pump shaft.
The end of the pencil is sticking into the weep hole.
[thanks to dodgeram.org used with permission]