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Old 08-16-2014, 07:35 AM   #1
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Another possible clutch problem question

Sometimes when I start my YJ it starts to move, even with the clutch depressed all the way. It does this when started in reverse also.

This is a 91, 4.0, ax-15.

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Old 08-16-2014, 08:37 AM   #2
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Clutch is not disengaging all the way, could be in the slave cylinder , master cylinder, air in system, check fluid level in reservoir to make sure it is normal level, possibly a line leaking. If it is intermittent a good chance it is in the hydraulics of clutch system and not mechanical

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Old 08-16-2014, 03:37 PM   #3
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Thanks for the help Mr White. I didn't find any leaks and the fluid level looks fair. My master cylinder has already been replaced before and the replacement doesn't have a full line indicator inside the reservoir. I used a tooth pick to feel for the indicator, but don't feel a grove or a ridge. The fluid is clear and the level is about an inch from the top of the reservoir.

Is there a way to bleed the system by myself?
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Old 08-16-2014, 05:15 PM   #4
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There is no easy way to bleed the system by yourself. Get a 3/8" ID hose and connect it to the hex collar with a hole down the center, get a helper that can follow directions and bleed the slave like you would your brakes (push down, hold, crack bleeder, close bleeder, repeat).

Be sure to start with a full master cylinder, and don't let it drop to low (refill every 2-3 bleed attempts).

Typical clutch failure results in slipping, not constant engagement, so this is likely a slave or master issue. If bleeding it doesn't fix it, you likely have bad slave cylinder (which requires transmission removal on the 91 as it is an internal slave cylinder).

Good luck
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Old 08-16-2014, 07:10 PM   #5
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Thanks shelby, I'll get some help. I read today, if bleeding doesn't help, then change out the master first and see if that fixes the problem. I read it can be bad even without any leaks. If that doesn't fix it, I guess there's only one more solution, pull the transmission and replace just about everything while the transmission is out. At least that's the way I understand it.
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Old 08-16-2014, 09:19 PM   #6
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Master cylinder can be bad without leaking, internal seals allowing fluid bypass, longer pedal is held down more clutch engagement you will feel. I would definitely try the master first before pulling transmission! Good luck
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Old 08-17-2014, 06:23 AM   #7
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Thanks again Mr. White.
I've looked over everything and been reading a lot of info on this subject. One thing I haven't seen is, can I leave the master cylinder cap off while I do the bleeding process?
Also, some people say to use oem parts(I'm guessing that means mopar?), even though they're more expensive. The Mopar replacement is about 90.00 more. What's your take on this or anyone's take on this?
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Old 08-17-2014, 06:56 AM   #8
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You can leave the cap off when bleeding system, just make sure you keep the level up. Oem parts are good quality but you are paying the oem price. Aftermarket quality is good also, the only time I use oem is when the part is not available through the aftermarket.
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Old 08-17-2014, 07:03 AM   #9
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Check out autozone. The master cylinder is less than 25.00 and the slave is less than 70.00, both come with a lifetime warranty so if there ever is another failure you won't pay for the part again.
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Old 08-17-2014, 07:13 AM   #10
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Ok, the cheapest I found was around 40.00 but I'll check autozone. Thanks for the bleeding tip and all the info you've helped me with.

Greg
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Old 08-17-2014, 07:21 AM   #11
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FWIW, if I had to pull the slave, I would go ahead and buy the pre-bled system (slave, master, and line). Autozone stuff is ok, but their lifetime warranty doesn't mean anything to me when I have to drop a transmission because a $40 part failed in a couple of months. If you can spare the extra cash, buy the complete system from NAPA or rockauto (I prefer napa).
It is rare, but a deteriorated hyd. Line can also push trash into your slave and cause a failure.
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Old 08-17-2014, 07:29 AM   #12
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I'm not dropping the transmission first, I'm going to replace the clutch master cylinder first and see if that's the problem.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Hey Mr. White, my local AZ wants 39.99 for the cm cylinder. Location, location, location.
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Old 08-17-2014, 08:44 AM   #13
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Quote:
Originally Posted by shelby987 View Post
It is rare, but a deteriorated hyd. Line can also push trash into your slave and cause a failure.
Should I try blowing air through the line while it's disconnected at both ends?
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Old 08-17-2014, 08:41 PM   #14
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Figures! Location is the key. I would try that first for sure. I would not blow air through the lines, when you install the new master cylinder and open the bleeder on the slave to bleed the system. This should flush things through until clean new fluid is present.
Prebled systems are nice but not as easy to install with an internal slave as they are with external slave. Not that hard to bleed the system if you have a friend to help out, takes a matter of minutes.
There is a possiblity of deteriorated lines and a blockage, attempt to capture old fluid and inspect it closely.
Best scenario is always change everything in the system, but if you are on a tight budget you are taking the right steps.
As far as Autozone parts go, I spent three years as a store manager for them and in the aftermarket as well as oem there are bad parts out of the box and premature failures, try taking a part back to a dealership after it fails In two years.
Most of the problems I saw was with an improper installation and of course the customer stating we sold junk parts.
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Old 08-17-2014, 09:06 PM   #15
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I just got back from picking up the new cmc and some Prestone synthetic brake and clutch dot 4 fluid. It says it can be used instead of dot 3 but has a higher boiling point.
I think I'll change it out next weekend. I'll be on vacation and I'll get some help to bleed the system.
Thanks again for all the help and the tips.
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Old 08-17-2014, 09:15 PM   #16
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Your order does sound correct, and I agree with White, don't blow air through the line, the concern is not foreign debris, the issue is typically degradation of the internal lining of the hydraulic line itself, if that is the case, pressurized air will likely speed this delamination process up.

With regard to part quality, my concern is rarely whether the part can be returned after failure, but whether the part will fail. The internal slave cylinder is a bad idea from the get go (which is probably why Jeep switched to an external slave, even the factory parts are failure prone). The load this part sees, the heat cycles it endures, and the pressures it operates under while in use cannot be duplicated in the factory during quality check procedures.

My part selection general hinges around several factors, the order breaks down this way:
-Difficulty to replace said part if it fails (an internal slave and rear main seal are at the top of this list)
-Severity of failure if said part fails (can I drive home safely if it fails, or am I out for a $100 tow)
-Can a cheaply made part be easily detected? (A good example of this is brake rotors they look the same, but material quality cannot be detected until you have warped Chinese rotors)
-Price difference between the cheap part and the expensive part
-Odds that a defective / low quality part would actually be detected at the factory (a low quality hyd. seal is an example of something that will pass at the factory, but fail in a month)
-How long do I plan on keeping said vehicle.

Good luck with your replacement, if you plan on keeping the YJ for a long time, it might be worth keeping an eye open for an external slave setup from a 94+ YJ.
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Old 08-17-2014, 09:29 PM   #17
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Thanks shelby. Ok, no air.

"if you plan on keeping the YJ for a long time, it might be worth keeping an eye open for an external slave setup from a 94+ YJ". That's good to know, I'll keep looking on Craigs List.

Thanks for your help and advice also.
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Old 08-23-2014, 11:37 PM   #18
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Just an update.
I put on the CMC today and bled the system, by myself. I cut a 21 inch long piece of oak as a makeshift clutch pedal hold down stick. Got the system flushed out completely with fresh fluid. I took it for a test drive, it shifts up and down ok, but the clutch pedal feels weaker. I guess I need to get someone to help me bleed it.
It'll take a couple of days of normal driving before I'll know if it cured the original issue.

Thanks for the help.
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Old 08-28-2014, 03:32 PM   #19
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Ok, my brother just help me to bleed the system again. Clutch still feels mushy. My brother would pump the clutch 10 times, hold it in, I opened the bleed screw til it stopped bleeding, then I tightened bleed screw. We did that 10 times, still mushy. The fluid being bled out, looks clean and fresh.
Could it take more than 10 tries to bleed the system?
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Old 08-28-2014, 03:50 PM   #20
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If you have help, the best way to do it is short (not all the way to the floor) pumps of the pedal and then hold the pedal half way down, open the bleeder while keeping pressure on the pedal till it hits the floor. Then tighten the bleeder and repeat.

Sometimes it will take 20 or more times to get all the air out. When you bleed the system, each bleed will move the fluid about 1 1/2"-2" down the line, that line is 4-5ft. long. You can do the math.

Or the other thing that it might be is the MC isn't matched to the slave. meaning the stroke on the MC isn't moving the slave far enough. But if you can start the Jeep and engage 1st or reverse gear without it grinding, a soft or spongy pedal might just be something you will have to learn to put up with.
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Old 08-28-2014, 05:46 PM   #21
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Ok, I'll try again. As for the math, at 2" for each bleed, that's 30 bleeds for 5'.

I wouldn't like getting used to it though.

Thanks for the tips.
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Old 08-29-2014, 11:33 AM   #22
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My brother just left, this time we did 31 bleeds (done properly this time). It still feels mushy, but I'll give an update in a few days as I keep an eye on the fluid level.

I'm just trying to keep it updated for the folks.

Thanks
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Old 09-08-2014, 10:15 AM   #23
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Wow, time sure flies. I'm still having issues with the clutch, I guess internal slave is next to be replaced.

Thanks

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