Jeep_Dave

I have a 2014 JKU with 40k miles and a 6 speed manual tranny. I recently replaced my old hydrolocked 3.6 with a new/used one. When I replaced the engine, instead of buying a new clutch I swapped out the one from my old engine since it was still in good condition. After I got the Jeep running, I noticed that the clutch pedal was a bit soft. 100 miles later, it was EXTREMELY difficult to put the tranny into ANY gear. I've checked the brake fluid reservoir and it was about half way. I inspected the master and slave cylinder and they don't seem like they are leaking. I've tried to bleed the clutch but the peddle still feels soft. Also when I do get the Jeep in gear and have the clutch all the way to the floor, the Jeep inches forwards as if the clutch was engaged. The transmission also clanks when I put it into reverse but I've heard this is common with the 6 speed transmissions ?

My question to you guys is, do you think I need to replace the slave cylinder, master cylinder, or need to bleed the air out of the lines?

tjkamp

It sounds like you need to bleed the slave cylinder some more.

The slave is an incredibly stupid design. I have replaced mine twice, the first time I bled it the old fashioned way, pumping the clutch pedal, the second time I used a combination of a hand operated vacuum pump and pumping the clutch method. The first time it took 5.5 hours to bleed all the air out of the system, and get the clutch working correctly, the second time, with the vacuum pump, it took 4.5 hours. The problem with the slave is the location of the bleed screw makes it nearly impossible to get air out of the slave if it gets into the slave itself. Whoever designed the JKs slave cylinder seriously needs their ass kicked.

happy Jeeping!

Jeep_Dave

Man I understand your frustration. I'll definitely try to bleed the slave cylinder again later today. Do you have any tricks or advise on bleeding the slave cylinder? And if you don't mind me asking, what made you replace the slave cylinder twice? Was it leaking?

tjkamp

There has to be some sort of trick or equipment that I don’t know about, I can’t see a professional shop spending that much time bleeding a slave, but whatever it is is beyond me. The vacuum pump is nice because it turns it into a one man operation rather than having to have a second person pump the clutch pedal, but that’s about all I have.

I replaced it the first time because I was getting a horrific squeak any time I moved the clutch pedal, it sounded like something between the baying of a donkey, and nails on a chalk board. A couple of people on here described a similar problem, and said replacing the slave corrected the issue. Changing mine out made very little to no difference. But as everything was functioning normally I just went about my business. Fast forward 11 months, and one day getting out into the highway, I notice the clutch slip a little on the 3rd to 4th shift, when I went to make the 4th to 5th shift the pedal went straight to the floor, no resistance no nothing, and I was stuck in 4th. I managed to limp it home, where I found that apparently the piston in the slave cylinder (which is made of plastic) got stuck fully extended, and when I let out the pedal, and the hydraulic pressure was no long behind it, clutch fork came back and shattered the piston into at least 3 separate pieces. So now I’m on my third slave, and the clutch pedal still sounds like an angry donkey, and I’ve had the wrangler rattle in my TOB for right at 100,000 miles, so in a few months when I finally get around to swapping out the clutch I am going to get the whole kit from Centerforce and National Bearing (flywheel, clutch disk, pressure plate, TOB, fork, the works), and try to get rid of as many of the factory parts as possible.

Jeep_Dave

*** UPDATE ***

This weekend I tried bleeding the clutch again. After a few hours of frustration and getting brake fluid everywhere, I finally gave up. The clutch felt worse than before and noticed that fluid was falling out of the bell housing where the tranny and the motor meet. In a desperate attempt to resolve this issue, I purchased a new slave cylinder. Prior to installing the slave cylinder, I made sure to fill it with DOT 3 brake fluid and compressed the piston a few time to ensure that I got got all the air bubbles out. I installed the new slave cylinder and continued to bleed it. After about 25 cycles of pushing the clutch and holding it down while I open the bleeder valve, it finally seemed like I got all the air out. Every time I would open the valve, I would hear a "whoosh" as the brake fluid went up the clear nylon nose and did not see any air bubbles in the clear line that I was using to bleed the brakes. I turned on the Jeep and tried to put it into gear and NOTHING. Now I can't even get the Jeep to go into gear. I then shut the Jeep off and put it into 1st and turns it back on. The jeep started to move forward even though I had the clutch peddle all the way to the floor. The only other thing that I could think that would be wrong is the master cylinder or the clutch fork. I doubt that its the master cylinder because there are zero signs of leaks.
I'm really lost on what to do next. Any suggestions?

Side not: There was one occasion where I forgot to close the bleeder valve and I pressed then clutch and brake fluid came out the bell using of the transmission. Only a few drips unlike with the old slave cylinder. Any thought on why this happened?

dmwil

Wow, I hope you get it figured out. I had a Jeep dealer replace my leaking slave cylinder at 93k miles or so, and they did the whole job in less than 2 hours. I'm guessing they've got a device or method to bleeding that thing that works well. Mine felt perfect after the replacement.

Good luck!

tjkamp

I still would have to guess at air in the system, except for it coming out of the bell housing, if it is leaking out of the inspection port of the transmission, then the slave has burst, or is leaking. If it just sprayed everywhere out of the bleeder, and is dripping down all over the place, then the slave is fine. During the breading process, my clutch acted as you described: push the pedal, clutch doesn’t actually react, stuck in neutral, or stuck in gear.

The dealers must have some mechanical bleeding equipment, to get the “micro bubbles” out. My fluid kept getting super tiny bubbles in it (as visible in the clear plastic hose) and that was the only thing I could figure that was causing the slave to not actuate the clutch. Idk

mr72

Maybe you can bleed it with a vacuum pump or hand bleeder much easier if you remove the slave cylinder and raise it up into the air some? Sorry I can't be sure because I haven't really looked at mine.

However, to the OP, the problem is you "bled" the system with the clutch pedal on the floor. What you have to do is depress the pedal and allow it to push fluid (and air) out the bleeder valve. It does this because it's easier for the fluid to come out the bleeder valve than it is for it to push the plunger. then you release the clutch. After that you can repeat until there are no more air bubbles coming out the bleeder hose. You will have to pretty much continually add fluid at the master cylinder to keep it from going empty since you are basically pumping fluid from the master cylinder into your overflow bottle on the end of the bleeder hose. If you ever allow the clutch to be depressed while the master cylinder fluid is too low then it will suck air into the system and you will be starting all over.

The problem you have currently (no clutch release) is because you closed the bleeder valve while the clutch pedal was depressed. When you release the clutch pedal then it draws a lot of fluid from the master cylinder and probably wound up being very low or sucking in air again.

You just need to re-bleed, follow the instructions closely, and with any luck it'll work.

BTW if you kept the clutch, hopefully you kept the other parts too, like fork, throw out bearing, any sleeve/collar that's in there (dunno I haven't had mine apart), and pressure plate. Those parts are all sort of a matched set that stacks up to the right height for it to work. you might wind up mismatching the TOB/collar and pressure plate and end up with a no-disengage clutch (BTDT ... in a 240Z).

paintm4u

This system needs to be bench bled, I was a pumpup guy for a long time until I learned to bench bleed. This actually saves time and frustration. This is a good vid.
https://www.youtube.com/watch?v=8pZHTeLS4ik

Jeep_Dave

I actually sow that video too. But you can't remove the center rod out of the slave cylinder on a JK. Or can you?