Daily driver, master felt like it was going, 6 months or so ago. Pedal would go almost all the way to the floor before starting to engage.

Got a new (Chinese, cheap, but lifetime warranty) master, and all was good.

The other day, pedal went 1/2 way or more to the floor before engaging, but seemed to return to normal. Got home, and it was doing it again. Went out the next morning and it was 100% consistent, 1/2 way or more to the floor before starting to engage.

Went out this morning, and even worse, pedal to the floor, couldn't get it in gear, car starts moving.

Got a new master, and cannot bleed this thing. Bench bled the master to no bubbles. Put it on, and with someone pumping the pedal, went through an entire bottle of brake fluid, and every pump is the same at the slave: at least 1/2 air and half fluid.

The system is not leaking, so how can that much air continually be in the line? and why can't I clear it?

I'm thinking the MC itself. On a toughie that wont bleed (brakes) I cap the MC ports with (2) brass inverted flare plugs from the Edelman cabinet at the parts house & if it is bled out & in good shape the pedal will be rock hard with virtually no travel (easy pressure & stomping it) & if good then hookup/bleed one half to pin it down further. On yours I would take off the line & cap the MC & see how the pedal feels. Hope that helps you & holler how it turns out.

Watched a video on youtube where they push the fluid in at the bleeder and that pushes the air out.

I just recently bleed the air out of plane brakes. I was taught to use a pump oilier can with rubber hose attached to it full of special hydraulic fluid for plane brakes. I squeezed the oilier and pushed the fluid from the bleeder screws at the calibers and pushed the air out up through the lines to the master cylinders. Attached a rubber hose to the breather at the master cylinders and put the hose in a container so I could see when the system was bled. Took one try and and it was done.

I am pretty sure you can do the same thing purging air out of a hydraulic clutch.

This is the plane I was working on, not my own. It is hard to push the air down and out and easier to push the air up and out through the MC.

i never pump a clutch master [after bench bleeding, of course] when on the car. i just push pedal to the floor & hold, open & close the bleeder, rinse & repeat until the air is out. that can be very difficult at times. if that doesn't work, reverse bleed or hook up a mity vac type deal to suck out the air. this is just what has worked well for me over the years.

I'm going to go for one of these. Read a number of good reviews on it, off Harbors site as well.

This will do a better job for you, last longer, cost less and can be used after your done purging air out.
LINK

I bet the master cylinder re builders get tons of MC back that are perfectly fine.

Good idea! Funny how simple things can be, but it's seeing them that way first. I'll give this a try.

The slave up bleeding concept is nice but keep in mind it doesn't work so well across all applications. Some cylinders and bleeders are very restrictive and the ability to induce fluid into a line under pressure from an oil can pump mechanism is often extremely difficult. The amount of pumping to overcome pressure in the cylinder and lines can be more than the oil can can overcome. Worst yet is that the bleeders are usually far too short and do not allow the bleeder line to say in place. As an engineer, I have NEVER understood why bleeders are not 2x longer with multiple barbs to hold bleeding lines in position without fear of them popping off and allowing more air back into the lines (or pressurized fluid from running out). As usual, each application may and often does require different methods.

- EM

He is bleeding a hydraulic master cylinder for a slave cylinder for his hydraulic clutch, not car brakes. I do not disagree with what your saying for car brakes.

But I bet it will work for a simple setup like he has it should work.

I related his setup to bleeding the brakes on a small airplane. I has just recently used a oil can to push fluid from the caliber up through the plane to the master cylinder attached to the rudder pedals. The MC are small and one for each side. They are about the same size as H clutch master. So for 8 bucks I think it is worth a try. Simple to do with piece of vacuum hose no fittings needed.

Worked real well on these Cessnas and taught to me by a long timer airplane mechanic. It is how they flush the brakes on small planes during maintenance.

For brakes, I use a mityvac, and put teflon tape around the bleeder screw, to help keep it from eventually seizing to the caliper, and to help prevent air being sucked past the threads.
Last master/slave cylinder set up I bought came completely assembled, was all plastic, with fluid, and bled, all in 1 box. No bleeder screw on any of it.

He is bleeding a hydraulic master cylinder for a slave cylinder for his hydraulic clutch, not car brakes. I do not disagree with what your saying for car brakes.



My reference was and is to a clutch master and slave, not brakes. It all depends on what system you're working on and especially the bleeder screw diameter and side port sizes. I had a 1/8 NPT bleeder on my Wilwood slave and besides the extremely short tip that the bleeder hose didn't want to stay on, the port diameters were so tiny I couldn't overcome the resistance force with the oil can I have. Hence my earlier comment. I removed the bleeder screw and bleeder screw adapter and machined the adapter for a larger 5/16 NPT bleeder with larger ports. Resistance dropped and ease of bleeding went up dramatically. I also ended up with a larger head on the bleeder screw for better fit with the bleeder hose.

- EM