Dual-chamber master cylinders are a pain in the butt to bleed! They trap a lot of air, and must have the bench-bleeding operation done before they're installed. The early method of doing this was a couple of plastic lines installed from the output ports back to the reservoir, and the MC was pumped while mounted in a vise until all the air was purged out. (keep the tubes submerged in the reservoir fluid.) Now, a couple of plastic plugs for the output ports are supplied with the new MC, and the reservoir is filled with fluid, and the cylinder is cycled until all the trapped air escapes through the vent holes above the pistons. Yes, it will bubble and squirt a little fluid in the process, so replace the cover during the first few strokes of the pistons. Once all the air is displaced, install the MC, connect the lines, and bleed the remaining air through the wheel cylinder bleeder ports. It's nearly impossible to get all the air out if you install the MC dry!
Jerry
