Default Clutch Master Cylinder 1979 CJ7 

Old 11-07-2012, 12:42 PM   #1
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My 1979 CJ7 has been in our possesion 5 days, clutch master cylinder needs to be replaced. Morris and Omix ADA only carry Master Cylinder for 1980 and later CJ7 etc. They are mystified they don't have trace of what is used on 1979? The slave cylinder is avaialble. Does any one know if a 1980 Clutch Mster Cyl will work on 1979? Or where to find part for 1979? Thanks.

 

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Default Re: Clutch Master Cylinder 1979 CJ7 

Old 11-07-2012, 01:15 PM   #2
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Quote:
Originally Posted by salemvajim View Post
My 1979 CJ7 has been in our possesion 5 days, clutch master cylinder needs to be replaced. Morris and Omix ADA only carry Master Cylinder for 1980 and later CJ7 etc. They are mystified they don't have trace of what is used on 1979? The slave cylinder is avaialble. Does any one know if a 1980 Clutch Mster Cyl will work on 1979? Or where to find part for 1979? Thanks.
Sale,

Pull your master cylinder off , the key for replacement is going to be the bore size & mounting. In order to determine that......... you may have to pull it apart from the back to measure.
All of these systems have specific MC bore sizes that are matched up with a clutch slave of a specific bore size.
Pretty standard MC in that era would be a Dorman # CM106439 which is 13/16" bore.

 

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Default Re: Clutch Master Cylinder 1979 CJ7 

Old 11-07-2012, 05:02 PM   #3
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Thanks. So the key is to make sure the master Cylinder and slave are sized for each other. My proclivity to belt and suspender solutions is to replace both.

I wonder, did 1979 not have hydralic clutch when new and thats why I can't find it as a part? At some point in the past a 1968 V6 was installed and maybe the clutch gear was changed then. Lots to learn!

 

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Default Re: Clutch Master Cylinder 1979 CJ7 

Old 11-07-2012, 05:17 PM   #4
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Quote:
Originally Posted by salemvajim View Post
Thanks. So the key is to make sure the master Cylinder and slave are sized for each other. My proclivity to belt and suspender solutions is to replace both.

I wonder, did 1979 not have hydralic clutch when new and thats why I can't find it as a part? At some point in the past a 1968 V6 was installed and maybe the clutch gear was changed then. Lots to learn!
That is what I thought............someone added that system. What type of slave cylinder to you have? I am assuming it's mounted off the bell housing?
The first big question: How well does the current system work? If your happy with pedal pressure and have enough travel at the slave to make the clutch work then replace it with like parts. You still may have to take them apart and measure the bore.

You get into bore sizes like this............smaller bore equals greater pressure and mechanical advantage, but requires longer travel and will push a lower volume of fluid..............so if the clutch is hard to push in... it could be your master is too large a bore versus the slave and the opposite.
I'm trying to make this sound simple but there is a lot of engineering details that do apply.
Most times the bore on the master is within .060 thousands of the slave. meaning perhaps 13/16" bore MC with a 7/8" bore slave.
Take some pictures of both.


 

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Default Re: Clutch Master Cylinder 1979 CJ7 

Old 11-07-2012, 05:37 PM   #5
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Every thing seems to work fine but loosing fluid on back side running down fire wall. My 79 MGB did smae thing when it got old. If we top up fluid every thing is good ...for a while. Travel seems fine, pressure ok as well. I suspect that since jeep is being driven by my son on daily basis instead of sitting, the cylinder is probably showing it's gray hair. Slave is on bell housing. I am going to throw my credit card at the problem ! Again thanks for the advice.

 

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Default Re: Clutch Master Cylinder 1979 CJ7 

Old 11-07-2012, 07:58 PM   #6
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Once you determine the bore size, just get a rebuild kit for both master and slave cylinder. They are pretty easy to rebuild. A lot cheaper than buying a new one.
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Default Re: Clutch Master Cylinder 1979 CJ7 

Old 11-07-2012, 11:15 PM   #7
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'79 Clutch master cylinder? ? ?

What are you guys talking about?

I own a '79 CJ5. I used to own a '82 CJ7. Neither one had a hydraulic clutch. They both had clutch linkages like this:

Manual clutch.
Crown Auto says the above parts are for Jeep CJs from 1976 to 1986.

What am I missing? I have a 304 V8 and used to have a 258 I6.


Maybe I remember some CJs such as 4 bangers had hydraulic clutches. What engine do you have, salemvajim? Please fill out your profile.
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Last edited by BusaDave9; 11-07-2012 at 11:21 PM..

 

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Default Re: Clutch Master Cylinder 1979 CJ7 

Old 11-08-2012, 01:19 AM   #8
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Quote:
Originally Posted by BusaDave9 View Post
'79 Clutch master cylinder? ? ?

What are you guys talking about?

I own a '79 CJ5. I used to own a '82 CJ7. Neither one had a hydraulic clutch. They both had clutch linkages like this:

Manual clutch.
Crown Auto says the above parts are for Jeep CJs from 1976 to 1986.

What am I missing? I have a 304 V8 and used to have a 258 I6.


Maybe I remember some CJs such as 4 bangers had hydraulic clutches. What engine do you have, salemvajim? Please fill out your profile.
Busa,

Someone stuck a V6 in there in the past and must have thought adding a Hydraulic Master and Slave would be easier.
Its leaking and that's why he wants to replace it.........Just trying to give him some advice on the subject.
The 1980 CJ had the Iron Duke 4 cylinder in there w/ a Hydraulic MC & Slave. The firewall was even pre-punched for the MC.

 

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Default Re: Clutch Master Cylinder 1979 CJ7 

Old 11-08-2012, 11:22 AM   #9
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Please give me a break with the profile info. We've have had the vehicle 6 days now. I dont have all the info for the vehicle yet till we crawl under. But it has 1968 Dauntess 225 engine and my bet the master cylinder was retrofitted. Interesting the fire wall looks like it was punched out for the Clutch MC like the 1980 firewalls. I don't have a good history on the velicle so we are going to learn as we go. Basically we can't find a part for factory Master cylinder for the clutch because they didnt make them that way. Thanks.

 

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