Okay guys, before you tell me that it works due to low brake fluid, how does the guts really work? Has anyone taken one apart? Shouldn't matter whether it's disc, drum, or a combination of. I was curious how the guts actually send a electrical signal that it is having a low level of fluid passing among it's chambers. After inspecting the insides, I couldn't determine how the plunger actually engages. Seems when you tighten the outside nut, that it holds all the internal parts in place and won't allow the 'inner' shaft to move in or out. Anybody actually been there, done that?

Check this link.

Linky (http://www.babcox.com/editorial/bf/bf50014.htm)

Hey Pate,

You sent me exactly what I needed. Figure 20 from your Linky is the closest to what I have. I took an old drill bit and past it thru the openings on the ends and pounded out the guts which was a couple of springs, a piston assy and the ends. After cleaning them up and honing out the cylinder, it actually works now. I would bet that most combination blocks are stuck in the open position. That would be from old brake fluid sitting there and turning in to moist sludge. If a driver had a 'low fluid level' they wouldn't get an electrical indicator light.

Thanks again,

Paul Lower SoCal

Very nice and informative article. That's what I love about this site! Thanks Paul