Bleeding internal Slave

[jbellingham]

I recently changed the clutch, and have been having trouble getting the internal slave to bleed.   I’ve probably bled it by hand, with a friend pressing clutch petal about 10 times.   Every time I bleed, I get a little burst of air and then clutch its nice and stiff.  I drive it for a few miles, and petal gets spongy again.   I can’t imagine that there’s this much air in the system, but can’t see any fluid leaks.   The master cylinder is fairly new, and was not acting up before I changed the clutch.

 

Any suggestions??  Is it normal to take this long to eliminate air from the system??   

[yxmj]

Take a moment and describe your exact technique ....."bleeding by hand" doesn't count as a description 

[jbellingham]

Ok - I lay under the truck while someone else sits inside.   They pump the pedal a few times, then hold it down.   I open the bleeder valve allowing air and fluid to come out, then close the valve and tell them to take foot of clutch.   I repeat a couple times until there’s no air, and clutch pedal seems firm.   Then I fill reservoir with fluiid, making sure that the level doesn’t drop too much.  

 

Then I drive for a few miles, clutch gets spongy and I repeat all over again.   I’ve probably done this about 8 times now, and every time there’s more air coming out of the bleeder.  

[87MJTIM]

Is the master cylinder level dropping after driving it around?  Have you checked inside the cab for leaking of the MC over top of the fuse box?

 

Maybe the MC internals are failing and fluid is getting past the seals.

[DirtyComanche]

You don't pump the pedal.  All that does is causes air bubbles to become entrapped in the fluid.

 

The clutch is bled by opening the bleeder screw, pushing the pedal to the floor and holding it there, and then closing the bleeder screw.  Release the pedal and repeat.  I've also had no issues pushing the pedal down, wedging it with a stick, and then opening the screw and closing it when the fluid flow stops, but that is not what the manual recommends.

 

I put a hose on the end of the bleeder and run it into a bottle also, as this makes it less likely to accidentally pull air back into the system.  Plus it saves the mess.

[DirtyComanche]

That said most likely the slave cylinder has a pinhole leak in it, or one of the orings on the pressure and bleed lines, or the actual hose has a pinhole leak.  If you get it bled, even poorly, it should stay bled.

 

Since you have an internal slave, it makes it very hard to see small problems until it blows up completely.

[dvitha]

If you bled it like above said. no pumping, but slow push while you open the bleeder , and once to floor hold and shut bleeder. You can also use a vacuum gun if you have no one to push and hold for you. if above is done, I bet you have a small leak. Either on the slave to line connector or even on your master. When I replace a slave I replace the line and the master clutch. A small crack in your hose may not be able to be seen when cool and under the truck. However with heat from driving and use the fluid expands and the rubber flexes more so. At that point can let in a small amount of air. Seen it happen more than once here in the shop.

[Eagle]

Did you replace the flex hose when you replaced the slave cylinder? If not, replace that and report back.

[boxyjeep]

You probably have a leak in the hose.  I also ran into a ton of issues when bleeding an internal slave a few years back.  I succeeded by letting it "gravity bleed" for awhile by opening the bleeder and just letting it slowly drain while making sure it was topped off from above for awhile, and then switching to traditional bleeding afterwards.