Shimano GRX RX 815 Series Dealer's Manual page 163

MAINTENANCE
SHIMANO genuine mineral oil replacement
22.
Tighten with a bleed screw to which an O-ring has been attached.
Tighten with a bleed screw until oil flows out to make sure that no air bubbles remain
inside the reservoir tank.
Bleed screw
Bleed screw
0.5 - 0.7 N·m
O-ring
NOTICE
• Do not operate the lever. If operated, there is a risk that air bubbles may enter
the cylinder.
163