One additional comment about evacuating a system that has water in it. The water is likely in liquid form and will possibly be "under" an oil film. To remove this water, a high vacuum must be held on the system for a long time ... even in hot weather, I like to keep the pump running for two hours, then shut off pump holding vacuum on system (hoping to get the water to move from liquid to vapor so it can be removed). The pump may be cycled several times with corresponding "off" periods to convince me the water has been removed. We're talking a day ... sometimes also overnight ... to evacuate a car system.