1999 GMC Sierra 1500 Pickup Owner's Manual - Page 327

Brake Master Cylinder Your brakemastercylinderishere.It is filledwith DOT-3brakefluid. K2470 Thereareonlytworeasonswhythebrakefluidlevelinyourmastercylinder mightgodown.Thefirstisthatthebrake fluid goesdowntoanacceptable levelduringnormalbrakelining wear.Whennew liningsareputin,thefluid levelgoesback up.Theotherreasonisthat fluid isleakingout of thebrake a leakmeans system. If itis,youshouldhaveyourbrakesystemfixed,since So, it thatsoonerorlateryourbrakeswon'tworkwell,orwon'tworkatall. fluid won'tcorrect isn't a goodidea to "top off" yourbrakefluid.Addingbrake a leak. If youadd fluid whenyourliningsareworn,thenyou'llhavetoo much fluid whenyougetnewbrakelinings.Youshouldadd(orremove), brakefluid,asnecessaryonlywhenworkisdoneonthebrakehydraulic system. CAUTION I -\ If youhavetoomuchbrakefluid, it canspillontheengine.The fluid willburn if theengineishotenough. You orotherscould he burned and vehicle be your could damaged. Add . ake fhid nnlv en wn is doneonthebrakehydraulicsystem. Refer to the Maintenance Schedule to determine when to check your brake fluid.See"PeriodicMaintenance"intheindex. To Check Brake Fluid: You can check the brake fluid without taking off the cap. Just look at the windowsonthebrake fluid reservoir.Thefluidlevelsshouldbeabovethe 6-49