• Notice for iPhone users: DO NOT use the image size reduction option when uploading photos to the forum. This causes portrait images to post as landscape. We have added a warning to the image insert pop-up as well.

Clutch master cylinder that doesn't leak?

gpassida

gpassida

Basic User
Member
City
Redding
State
Ca
What have you used for a clutch master cylinder that has lasted years without leaking from the seal on the firewall side?

When I rebuilt my Scrambler, that had the 4-cylinder engine new, I kept what appeared to be the stock master cylinder. I believe it was on there for 40 years and didn't leak. Or at least the 23 years I've owned it without leaking. I thought I should replace it with a new one. I had a choice to use the crown unit below that looked exactly like my original. Or use a newer design with a plastic tank. I preferred the cast piece as it has one less seal to deal with and would likely outlast the plastic parts of the newer design.

Crown unit that looks like what I took off:
1763699684669.png

The new style looks like this:

1763699780649.png

The problem I have is the Crown replacement I installed leaked. I warrantied it with Summit and they send a new one. Now that is leaking.

Is it just bad luck or are these just that bad?

Are the plastic new style better?

Any tips would be appreciated.
 
I’m pretty amazed yours lasted that long. My original probably lasted 10 years then I rebuilt with a kit. That lasted maybe 5-7 years. Didn’t have luck with rebuilding a 2nd time and bought one with the plastic little reservoir . That one lasted maybe a decade. I have a YJ one now. I have this one in the spares box for the next one up. They make 3 size boresIMG_0232.pngIMG_0230.png
 
Belizeit said:
I’ve heard this is the correct one for the 6 cylinder with hydraulic.
Click to expand...
That Luk one looks just like the two Crown ones that I had leak.

I am seeing if the Wilwood (made in USA) one might work. The measurements seem to match up. However the bore size is .75 where I think the stock bore size is .8125. Apparently the smaller bore will make the pedal pressure lower. Not a bad thing but it may also impact the release stroke when using the clutch.

Also, the Wilwood has a threaded rod end to attach to the pedal, not the eye like the standard units.

1763850026362.png
1763850053978.png

But maybe I can find an eye to thread on like this:

1763850092316.png

If anyone has done this, let me know!

If it can work, the Wilwood seems to be a much higher quality unit and has a rebuild kit available.

They do also make a remote reservoir version that has larger bores including .81 like the stock unit.
1763850271811.png

1763850329828.png
 
Yeah I’m pretty serious about using the Wilwood. I ordered a rebuild kit with the clutch master and a heim joint. There’s a video of a guy doing it on a 1st gen. YJ
 
Belizeit said:
Yeah I’m pretty serious about using the Wilwood. I ordered a rebuild kit with the clutch master and a heim joint. There’s a video of a guy doing it on a 1st gen. YJ
Click to expand...
@Belizeit Do you know which specific heim joint you bought? (to fit on the clutch pedal peg)

Also, the stock Jeep line fitting is 7/16"-20 inverted flare. The Wilwood is 3/8-24. Will need an adapter.
 
gpassida said:
@Belizeit Do you know which specific heim joint you bought? (to fit on the clutch pedal peg)

Also, the stock Jeep line fitting is 7/16"-20 inverted flare. The Wilwood is 3/8-24. Will need an adapter.
Click to expand...
No I already removed it from the packaging and buried it in a box of spare parts. I may have to file it down some. I will have to look at the line fitting. It’s a flexible line from Novak I’m using.
 
@Belizeit I think this is the video you mentioned:

I just ordered the Wilwood Clutch Master Cylinder plus the other parts to try it. Probably not likely to get them in and do the install until after Thanksgiving weekend. We're traveling to Monterey.

Once I get it in and tested, I will post my findings and all the specific parts I used.
 
Update. The Wilwood 260-15098 is a nice unit but the smaller 3/4" bore size is not going to work. I got it installed with a heim joint that I extracted the ball from. Spent a lot of time bleeding it to make sure that was good and then adjusting it at the pedal with the threaded rod and also at the slave cylinder with the threaded rod that goes into the clutch fork. It just does not move enough fluid to move the clutch fork far enough.

I also took it to my trusted transmission shop that did my NV-4500 transmission rebuild. They tried and agree that it does not move enough fluid.

1766466838811.png

The stock bore size is 13/16". So I will have to go with something else. The Wilwood 260-15092 remote reservoir version does come in the 13/16 bore size and would work. The problem is the remote reservoirs are going to be a pain to get higher than the master cylinder. I will call them tomorrow and see if they have smaller options than their 4" high 4oz remote reservoir.

So I may just give up and get a Doorman CM106439 to put in with its plastic reservoir. This unit looks just like the Napa/O'reily/Autozone versions. They have the 13/16" bore. Who has had good luck (5+years with no leaks) with any of those units? They all look the same and are probably just rebranded for the source.

1766466606079.png

1766466634701.png
1766466656964.png
 
Well that’s a drag. Sorry to hear that. I’m using the YJ replacement which looks to be 11/16. Works pretty well, but wondering what 3/4 would be for mine. Good luck with the project.
 
Here is my update.

I decided to put in the Autozone Duralast version of the clutch master cylinder. The Doorman, O'Reilly and Napa units all look the same with minor variations on the plastic reservoir. Went with the Duralast as it has their "lifetime warranty". So, if it leaks at any point, I can get a replacement.

It is a direct drop in. Installed it, bled it easily and it works great. Smooth clutch pedal operation and bottoms out on the floor, not inside the cylinder.

Now we wait and see if it leaks in an unreasonable amount of time. I went through two new Crown all cast replacements. (lower one in the below pic) Both leaked inside under the dash from the seal at the rod entry area.

1768588318996.png

A visual inspection seems to indicate the Duralast seal area is tighter and slightly higher quality. But it's hard to really tell because it is brand new vs the 8-month-old Crown one that leaked in that area. Time will tell...

1768588528578.png

The plastic reservoir is taller and it takes some "fiddling" to get the lid off to add fluid. But the positive side is you don't have to take the lid off to check the fluid level.

Can anyone tell me if I reinstalled the grill support rod in the proper position under the firewall tab? (see circled area) If I move it to the top of the tab, it will provide more clearance on the lid.

1768588836573.png

Got a few trips coming up so I hope it remains leak free!
 
So what year vehicle / model / engine did you request from AZ of the Duralast one ? Or what did you request ?
 
Belizeit said:
My 7 came with a 4 cylinder also. I’m trying to remember what transmission you are running ? And what slave cylinder you are matching it up to ?
Click to expand...
I run a GM NV-4500 5-speed transmission with the 6.34:1 first gear. And I run a Napa 73173 Clutch slave cylinder.

1768668815136.png
 
You must log in or register to reply here.
Back
Top