You shouldn't have to put fluid in unless you open the bleeder plug. If you do that, then you have to bleed your brake system. Not a bad idea anyway if the fluid's been in there for longer than 2-3 years. Be sure to watch the reservoir in the engine bay so it doesn't over flow, try to catch all of the overflow if it does, or suck out some excess with an old turkey baster. Just try not to get the fluid on the paint. If you do lose some from the reservoir, you will need to add it also.