I noticed my rear brake felt spongy recently. I checked the fluid level. It looked low so I added some fluid and decided to bleed the rear brake. I attached a hose to the bleeder valve, started pumping the brake pedal and fluid began coming out. Then ... it stopped, and bubbles appeared in the hose. There was no back pressure when I pressed down the brake pedal. I checked the fluid in the master cylinder and there was plenty. It seemed like fluid wasn’t getting into the brake line from the master cylinder.
After scratching my head for several minutes, I noticed that the rubber plunger that had been attached to the lid and sits on top of the fluid had fallen into the master cylinder reservoir, and that all I was doing was pouring fluid into the underside of the plunger. The fluid was never getting into the reservoir proper. From appearances it wasn't very obvious.
Once I figured that out all was fine. Brakes bled and no longer spongy.
Spongy rear brake
Moderator: Moderators
Spongy rear brake
2004 Rockster