Can't bleed the slave clutch

[lgjonec]

Had to replace the slave clutch on a 2005 MK4 Jetta because I accidentally tore the boot. I can't get the air out of the clutch. I am bleeding with a hose attached to the nipple and I am opening it when the clutch is fully depressed and closing it before the pedal is released.

There are microfine bubbles in the stream that won't bleed out. I've been through three pints of brake fluid. It seems like there is an air leak somewhere in the system (but I had no problems with the system before). I think I might be hearing a hissing sound near the fluid reservoir when the pedal is depressed.


Any ideas?

[YMZ]

Welcome to the website!

These cars are designed for the hydraulic systems to be bled using a pressurized system... Motive makes power bleeders with the correct size cap that many people use, and some have made their own... Attention must also be paid to make sure that the fluid level in the brake fluid reservoir never falls below the feed hose to the clutch master cylinder... (it's positioned higher than the brake feed...)

HTH...

Yuri

[chittychittybangbang]

If the brakes were just bled, you could try a recirculating purge since you've already flushed 3 pints through the system. See FAQ for tips. Not for use with a single drop of old fluid! But can help with pesky bleeding. You could just have a bubble stuck in there which needs some vigorous working out. In rare cases you just have to bench bleed (pre bleed out of car).

Or the new slave is defective

[Ol'Rattler]

Originally Posted by chittychittybangbang

If the brakes were just bled, you could try a recirculating purge since you've already flushed 3 pints through the system. See FAQ for tips. Not for use with a single drop of old fluid! But can help with pesky bleeding. You could just have a bubble stuck in there which needs some vigorous working out. In rare cases you just have to bench bleed (pre bleed out of car).

Or the new slave is defective

You need to keep the M/C full. Cracking the bleeder 3 times will introduce air back into the clutch because the clutch tap is so high on the M/C.

You can take a hose from the bleeder and put the other end in the M/C. As long as you keep the M/C full, all the air will get worked out when you bleed.

When I changed my slave, I went through less than a liter of fluid but I made sure the M/C level never got low.

[NIW]

I am having a similar issue, however, can anyone tell me if, after diligent bleeding of the slave ( 10 + times over the last two months, not correcting the issue after every attempt however) , and the car is back to shifting like butter it will without warning, go back to not fully disengaging - minutes, days or weeks later. Here's the part that is blowing my mind! ; it will go back to fully disengaging on its own, it just did it on the drive back home tonight. Air in the system is air in the system is it not? how could the problem rectify itself like it is? Help - what am I looking at here. Thanks for taking the time.

[chittychittybangbang]

Yes, once you get a bubble in clutch line, it usually stays there for a while. Maybe related to clutch slave cyl leak ? Very unusual for it to fix itself.

[NIW]

Originally Posted by chittychittybangbang

Yes, once you get a bubble in clutch line, it usually stays there for a while. Maybe related to clutch slave cyl leak ? Very unusual for it to fix itself.

Diagnostically I have to consider the following: 1) Since I am not loosing any system fluid over the past 2 months (2000 km) of driving, I have repeatedly flushed the clutch system like it had food poisoning and the fact that the clutch pressure restores itself , air in the line has to be considered secondary to the issue. 2) There must be a mechanical/hydraulic malfunction that reappears ; like spinning Pat Sajaks wheel of misfortune " Loose a Clutch". Therefore I ask, is there any way an O ring or some sort of pressure seal could be moving around/ failing and then correcting itself in its journey in either the Clutch master cylinder or in the Slave cylinder? and if so which one would have the greatest chance of producing this type of migratory failure? Or, is there any scenario where I have made a gross mistake when installing the 5 speed swap and my clutch,flywheel and or transmission are about to fly apart?. Any thoughts or recommendations would be appreciated from the TDI community.

[chittychittybangbang]

I cannot think of any failure like this that would fix itself. My best guess is that it's a mechanical problem like you said, a seal which is fixing itself as it moves back and forth. It's not in the clutch-flywheel-lever because I cant see anything there which would affect clutch pedal travel adn then fix itself. If you figure this one out, please post a follow up!

[NIW]

I have just completed a closed loop bleed. With trusty wife by my side and watching the clear return tube NO air bubbles! I pumped the crap out of it. Now going for a drive. If not successful ( not being negative) which unit should I replace first? Any guesses.

[NIW]

Can't get out of the driveway. Think I will start with the Clutch Master Cylinder.