GMC 2003 Sierra - Manual (Page 423)

Checking Brake Fluid
You can check the brake fluid wHhoul taking off the tap.
Just look at (he brake fluid resen/oir. The fluid level
should be above MIN. If I1 isn't have your brake sysfenn
checkeci to see if ihere is a leak.
After work is done on the brake hydrauhc system, make
sure Uie level is above Hie MEN hul not ovar the
MAX rrtark.
What to Add
When you do need brake fliuid, use only DOT-3 brake
fluid. Use new brake iluid from
a seated container
only. See Pad D. ftecommen and Lubnajnts
on paije 6-13.
Always clean Ihe brake fluid ieservoir cap and the area
around the cap belore removing it This will help
keep dirt Irom eniering Ihe reservoir.
A CAUTION:
with the wrong kind of fluid in your brake
systern, your brakes may not work welk or
they may not even work al aif. This could
cause a crash. Always use the proper
brake fluid.
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