I have a 99 dodge grand caravan 3.3 liter it is

Around the plastic. At the cap or under the reservoir? Rinse it off with water, and watch it for a day. There is an "O"ring under the cup, but I think it maybe nothing to worry about. Brake fluid is water soluble so it will cleam up fine. Don't get any on your paint and rinse everthing off thorouglyAll cars have sweating around that part, even the rectangular reservoirs. The cap/cover is ventented and the fluid expands when it heats up. So never fill to tje top, Leave about 1/4 in from the top for expansion. This will help fluid from getting vented out..