master cylinder

[lacey and bella]

have a 48 gmc 1/2 ton, took out original mc and installed a dual bowl mc,looking at the plunger that goes into mc, about how much of it should go into mc, to work right, new at all this, just asking cause having problem bleeding brakes,front driver side seems good but other three not working out well.

[oldman3]

I'm no expert on brakes, but first I would check the depth of plunger hole on the old MC and then check the new one. See if they are the same. Are you sure that didn't give you a power MC, because it won't work, depth of plunger is different. With the dual MC you should be able to isolate the front from rear. I always bleed the back brakes first, starting with the longest line. Then do the front, longest line. If this was done after your earlier post on bleeding brakes, it may take a lot to fill the new lines....Jim

[wraprail]

Also the power brake m/c would normally be a larger bore size than the manual brake model.
Usually around 1 1/8"-1 1/4" vs 7/8"-1" on the manual type.