Quick help, slave cylinder won't bleed?

[Jackrabbit88]

Hey guys, I changed out a warn clutch and slave and wrapping up the job. Blead the master and now trying to gravity bleed the slave. But the slave won't gravity bleed. I can push the Peadle and get some fluid and air to come out the but I've heard you shouldn't do that and just gravity bleed it. Any thoughts?

 

[Shran]

My gut instinct is that you have an air bubble in the master that is not allowing fluid to pass, or the bleeder valve is clogged or not open far enough. Don't push the pedal, at this point you are better off removing the master and hose and bench bleeding those...then gravity bleed again. Pushing the pedal sucks air back into the master cylinder, further compounding the problem.

 

[2 bronco 11s]

Hey guys, I changed out a warn clutch and slave and wrapping up the job. Blead the master and now trying to gravity bleed the slave. But the slave won't gravity bleed. I can push the Peadle and get some fluid and air to come out the but I've heard you shouldn't do that and just gravity bleed it. Any thoughts?

I agree do not push the clutch pedal. Had the same problem , fooled with it for a few days. Pulled it all out and got another, it worked. Remove the line off the throw out bearing assembly. Using your hang push the clutch pedal down , minimum force. It should barely move , less than an1/8 inch. If more take it off and bench bleed it. The master cylinder must be hung upside down , rod pointing down.

 

[rubydist]

Those things are so difficult to bleed properly. The last time I struggled with that and finally bought a master and slave that were pre-bled and installed those. Problem solved.

 

[Dirtman]

I've never bled one of these but couldn't you just use a vacuum pump to bleed it?

 

[Roert42]

I've never bled one of these but couldn't you just use a vacuum pump to bleed it?

Not installed in the truck. The master is pointing up so air gets trapped there and it's almost impossible to get it out. I've tried forcing brake fluid through the slave, through the master and out the reservoir. still couldn't get the air out.

 

[pjtoledo]

I've never bled one of these but couldn't you just use a vacuum pump to bleed it?

maybe, it would depend how much pressure the check "valve" has

in theory you could push the pedal/plunger all the way down and hold it there. that would push any trapped air into the line going to the slave.
at that point a seal at the bottom of the plunger is pressed against the inlet coming from the reservoir.
that's the check valve, keeps fluid from going back up to the reservoir when the pedal is depressed.
the path to and thru the slave cylinder is open all the way. vacuum applied to the bleeder would have to overcome the check valve.
if the check valve has more pressure than atmospheric, vacuum won't work.
maybe applying pressure at the reservoir would force fluid past the check valve.
BUT, I'm not sure the hose from the reservoir could withstand the pressure as it normally has no pressure.


the bottom O ring is the check valve, you can see the MC plunger in the middle.

 

[Garth Libre]

So what was the point of having an internal slave. I had a Mazda Miata with the same 5 speed and the slave was bolted to the outside of the tranny. Bleeding it was simple. Why not just go with simple?

 

[Shran]

So what was the point of having an internal slave. I had a Mazda Miata with the same 5 speed and the slave was bolted to the outside of the tranny. Bleeding it was simple. Why not just go with simple?

I suspect it was a matter of (a) less moving parts and (b) applying force directly to the clutch fingers rather than the slave cylinder pushing against something that pushes against something else. I bet it is also cheaper to manufacture a plastic slave cylinder with a spring and bearing attached to it as one piece instead of a slave cylinder, clutch fork and throwout bearing.