DAELIM ET-250 Service Manual page 143

Eventually, you can take all brake shoe out the hub.
There are two kind of brake linings as shown in picture
TO REPLACE THE BRAKE HYDRAULIC OIL
Loosen the bolts and open the cover
Loosen the bolt and drain the used oil out.
Tighten the bolt after the used oil being drained out
completely
Bolt
Add the brake oil (Dot 3 or Dot 4)
Keep oil level at least half of the cup in order to avoid
air in the brake system.
Loosen the bolt to vent the air from brake system.
Tighten the bolt if there isn't any air in the brake system
Tighten torque 40~70kgf-cm
Pull left brake lever slightly in order to extract air from
brake system
Fill the brake oil in the level shown on the cup
when no air comes out
Assemble the cover