You need to loosen the 19mm bolt first.

When loosening the bolts on the water and steering pump pulleys, leave the serpentine belt on. It helps to give you a non slip grip on the pulley when slackening the bolts - use a pear of non slip gloves to grip the pulley and belt at the same time.

Depending on the market and AC unit installed you will need to remove the fan and Y bracket to get at the pump bolts. Some pumps are held on with allen headed bolts not regular bolts that a socket can be used on.