If you're adding brake fluid because the level is low, you have one of two things going on. Either you have a leak that must be addressed first, or you don't understand how brake systems work. Professional mechanics who have their customers' best interest at heart would never top off the brake fluid reservoir during other routine services such as oil changes. If we see the level is low, the first thing we do is search underneath for a wet area or other signs of a leak. The customer must be informed of that before we do any repairs they hadn't asked for.
If no leak is found, we will recommend a brake system inspection, and let the owner decide when to have that done. All disc brakes self-adjust by the pistons gradually working their way out of the calipers to take up the space left behind when the linings wear down. Brake fluid fills in behind those pistons. THAT is why it is normal for the fluid level to drop in the reservoir. Months or years later, when we install new pads, we have to push those pistons back in to make room for them. Doing so pushes the brake fluid back up into the reservoir, and the level goes back up to "full". When an uninformed do-it-yourselfer has filled the reservoir previously, the fluid being pushed back up gushes out of the reservoir and makes a huge mess. What gets on the body will eat the paint too. Professionals avoid this heartache by never topping off the brake fluid reservoir.
Tuesday, January 9th, 2018 AT 3:36 PM