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How do I bleed hydraulic clutch

I replaced the clutch in a buddies truck last weekend and am having trouble bleeding the air out of the hydraulic system. It is a master/slave cylinder set up. The master cylinder was replaced about 3 months ago because it was leaking. The slave is original. After several unsuccessful attempts to bleed the system I removed the slave cylinder to better understand how it works. It appears that is there was any proplem with it, it would either be seized up and not work at all or it would be leaking fluid and have a noticeable drip coming from it. It has neither. I then removed the master clutch cylinder to get a better understanding of how it works. Holding the master clutch cylinder in my hand, I held my finger over the outlet connection and used a screwdriver to press the piston in, as the clutch rod would do if the clutch pedal was depressed. It did pressure up as expected. It appears that all of the components are working as they should. Is there a trick to bleeding this system. If I fill the master reservoir and bleed the clutch as I would a brake system will that do the trick? i.e. pump the clutch pedal then hold it in, open the bleeder screw on the slave cylinder to push the air out, then close it, release the clutch pedal and repeat the procedure until the clutch works as expected.

Reply to
gn145022
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That's the procedure, being sure, obviously, that the reservoir doesn't empty during the process. If it simply won't come up to pressure then the master must be faulty, again.

Reply to
Battleax

Usually you can bleed them just like brakes. Sometimes though that method does not work. pressure bleeder sometimes has to be used, and sometimes a vacumm bleeder is needed. There have been posts on here where the clutch system had to be reverse bleed. If you get a good pedal and then it goes away, then possibly there is a problem with the clutch master or slave. When using a vacumm bleeder limit the amount of vacumm applied, I have had instances where it turned out the vacumm was so strong it partially collapsed the cups and actually sucked air into the system.

Whitelightning

Reply to
Whitelightning

Yes. I just did mine a few months ago. I did it by myself which as a little bit of a pain. I pumped the clutch about 20 times and then wedged it down on the floor. I then opened the bleeder screw just a but on the slave cylinder. Air hissed out and then a little brake fluid dripped down my arm (that smell takes forever to wash off). I did this about 7-8 times before very little air was being released and it was all fluid. I friend then told me that I should have pumped the clutch slowly 20-25 times. I just pumped it quickly and I think this caused all the air in the lines to break up into tiny bubbles. The fluid looked like it was milky as a result. The last time I went inside for about an hour and then bled it one more time. At that time, I think the air had settled and the fluid was clear.

With the clutch push in, you only need to turn the screw (bolt) just a little. Then close it right back up.

Reply to
Todd Copeland

SNIP

Here is a very important tip... Jack the front of the truck up, or park the truck facing up a stiff hill. The master and slave bores are long. If they are facing "down" toward the ground, the air gets trapped in the back of the bores (away from the bleed screw on the slave), and you'll never get the air out... Jack that sucker up. It'll be so easy to get pressure, you'll think its magic.

Been there... Done that.

HDS

Reply to
HDS

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