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Clutch Master Cylinder

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Old 08-25-2014 | 04:48 PM
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Exclamation Clutch Master Cylinder

Hello all,

I would just like to ask a quick question re: the CMC on my 93 Cherokee.

It's been hard to put it in gear especially from a complete stop and it has gotten worse so I decided to take a look under the dash and under the hood. What I found is that the clutch doesn't travel as far as it used to and when I investigated a bit more, noticed that the CMC has some play on the section of the firewall that it is attached to. I have tightened up the bottom screw that holds it together but that did not help at all since the actual wall is moving with the whole CMC every time I push in the clutch pedal.

Please advise as to what further steps I should take and all input is appreciated.

Thanks so much for your help!

Last edited by rzrxn; 08-25-2014 at 04:51 PM.
Old 08-25-2014 | 09:50 PM
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Sounds like the firewall is flexing or broke. If so you may need to fabricate a plate to reinforce. Inside would be best so the relative position of the Cmc to the clutch pedal is unchanged.
Old 08-25-2014 | 11:37 PM
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No real help here except for a story. 66 Ford F-250. After 20 years of abuse, the left side panel was cracked free, at the rear where it meets the bed. I'd need to hold it in so the tale-gate latch would hit right. The whole deal with the tail-light and all was loose. A neighbor happened to be a talented welder. With a gas torch he went over a bunch of little cracks, (and some bigger). Friggen rock solid. That was in about 86. I still have the truck, and it's still solid. Hitten all those little hairline cracks did it well.
Old 08-26-2014 | 08:54 AM
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could also be indicative of a throw out bearing going. The harder pedal pressure required to make it move means you're pressing on the pedal harder, meaning the mount flexes more. How many miles on the truck, and when was the t/o bearing last replaced?
Old 08-27-2014 | 09:52 AM
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Originally Posted by mhoneyc
Sounds like the firewall is flexing or broke. If so you may need to fabricate a plate to reinforce. Inside would be best so the relative position of the Cmc to the clutch pedal is unchanged.
I had the same thoughts when I saw the wall moving. I will need to check for further damage within the firewall. From what I can see, the wall looks fine but it doesn't seem so when the clutch pedal is pushed down to the floor. It looks like the CMC is going to burst out of the wall.

Originally Posted by DFlintstone
No real help here except for a story. 66 Ford F-250. After 20 years of abuse, the left side panel was cracked free, at the rear where it meets the bed. I'd need to hold it in so the tale-gate latch would hit right. The whole deal with the tail-light and all was loose. A neighbor happened to be a talented welder. With a gas torch he went over a bunch of little cracks, (and some bigger). Friggen rock solid. That was in about 86. I still have the truck, and it's still solid. Hitten all those little hairline cracks did it well.
That's crazy! If the firewall really is destroyed or mangled around where the CMC sits, I wish I had the welding skills to DIY.

Originally Posted by CompleteCherokee
could also be indicative of a throw out bearing going. The harder pedal pressure required to make it move means you're pressing on the pedal harder, meaning the mount flexes more. How many miles on the truck, and when was the t/o bearing last replaced?
Hmmm, it has around 280k km and I replaced the t/o bearing & clutch around 2 years ago.


***

Thank you for all the input everyone! I am glad to hear your thoughts and it makes me feel so welcome in this community.

Another thing that I'm looking into doing, after I fix the firewall flex issue, is how to extend the rod from the clutch pedal to the CMC.
Old 03-04-2015 | 04:51 PM
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It's been a while since I've been here. Just wanted to send out a quick update.

My Jeep has been sitting in my garage since September 2014. I've been regularly starting it but the firewall flex issue is still at-hand. Every mechanic told me to just junk my Jeep and move on...

I REFUSE TO DO THIS!!!

This Jeep has been with our family since I was 12 years-old and my father loves the 93 Cherokee. I will do anything I can to get it fixed and would appreciate any help and advice that I could get from our community.

I will keep you all posted as of the progress and future plans for the vehicle. Rest-assured that my Jeep will be hanging around for a long while.

Cheers and thank you in advance!
Old 03-04-2015 | 05:13 PM
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Originally Posted by rzrxn
It's been a while since I've been here. Just wanted to send out a quick update.

My Jeep has been sitting in my garage since September 2014. I've been regularly starting it but the firewall flex issue is still at-hand. Every mechanic told me to just junk my Jeep and move on...

I REFUSE TO DO THIS!!!

This Jeep has been with our family since I was 12 years-old and my father loves the 93 Cherokee. I will do anything I can to get it fixed and would appreciate any help and advice that I could get from our community.

I will keep you all posted as of the progress and future plans for the vehicle. Rest-assured that my Jeep will be hanging around for a long while.

Cheers and thank you in advance!
My wife's jeep does the same thing, not sure on how much yours is flexing against my wife's, however I can say that it moves around 2 or 3 mm when pushed the clutch to the botton. The wife's used to be an automatic, and I made the conversion myself, from day 1 this is flexing, and there's no real issue with the clutch engaging/dissengaging propperly.

What I would do is to make a reinforcing plate, that can be weld (first option on the list) or rivetted to the actual wall, giving some more thickness on the material, and hopefully avoiding an unusual flex.

I know it may look bad (if it is cracked or something) however there are a lot more worse issues around Jeeps and we kept fixing them, this is something that can be fixed within a single day, just need to tackle it correctly, replacing floor boards is a lot more complex, and it is being done every now and then.

hope it helps
Old 03-10-2015 | 04:05 PM
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@lualchro:

Thank you very much for your input! I looked under the dash and saw that the wall is actually flexing.

It's very tight under there but I will try to get as much out of the way. Any suggestions of what material (type of metal) I should use for this job? I would also like to lengthen my clutch pedal rod. Is there any way I could do these both at once and hit two birds with one stone?

Again, thanks so much for your immediate assistance. Really really appreciate it. Take care.
Old 03-10-2015 | 05:03 PM
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Originally Posted by rzrxn
@lualchro:

Thank you very much for your input! I looked under the dash and saw that the wall is actually flexing.

It's very tight under there but I will try to get as much out of the way. Any suggestions of what material (type of metal) I should use for this job? I would also like to lengthen my clutch pedal rod. Is there any way I could do these both at once and hit two birds with one stone?

Again, thanks so much for your immediate assistance. Really really appreciate it. Take care.

Not sure what kind of sheet metal can be obtained without too much trouble in the US, but anything that is not really thin can do the job, in the past I have used the cover of old computers (CPU they call them around here) as scrap metal for making all kind of patches and reinforcements, it is free (if you have any old computer laying around waiting for the garbage truck) and the metal is thick and good, just need to be massaged to the appropiate shape.

If possible mount the reinforcing plate from inside, in that way it will distribute the push movement of the clutch to a wider zone on the firewall.


Edit:
for the pedal rod lengh, what I have seen in the past is that a nice bolt can be cut and weld to the rod, and the portion that attaches to the clutch pedal welded to a nut (from the same bolt), so you can turn it and have it fixed at the desired lenght. Keep in mind that the maximun travel is determined by the depth of the clutch master, once the piston has made it to the botton of the MC, there is nowhere to push it more, and also the pedal height will be increased if the rod is enlarged

Last edited by lualchro; 03-10-2015 at 05:09 PM. Reason: Adding info for the MC rod
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