Remove brake master cylinder cover. Rub your WASHED CLEAN finger over the bottom of the cylinder. Remove it then look - is it anything other than crystal clear brake fluid on the tip of your finger? If the answer is yes, get a complete system flush, the rubber seals are dissolving and this holds true for hoses, caliper seals, and brake cylinder seals. This is one of THE MOST OVERLOOKED maintenance checks for cars, pickups and motorhomes. It's plain nuts to look at the level and not check the bottom of the reservoir for black gook. Flushing the system can delay repairs by twice or even longer periods of time. Of course folks with six-inch thick wallets can ignore this advice :)