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Clutch Master Cylinder - Broken 3

D

DarrellXJ

NAXJA Forum User
Location
Washington
'93 Sport, AX-15, I-6

I've "snapped" 3 clutch masters in the past 6 months and I wanted to see if anyone else has had the same problem. The part is breaking at the point where the molded plastic and metal rod are formed together - photos attached. I'm trying to figure out if it's a part issue, or hydraulic line issue. I've got no confidence in either right now. O'Reilly's is happily replacing the part, but it's still an hour plus of my time to swap it.

Looks like from 91-93 Jeep used a nylon hydraulic line with a reverse flair, roll pin, and o-ring at the master; and a quick disconnet at the line leading to the internal slave. Bad design with lots of spots for air to leak into the system. I've bled it a number of times (with each mc change and other times) and the pedal pressure doesn't seem to take super-human strength to engage.

Anyone else had this "snapping" problem?

I've been using another forum, but I'm going to transition over to NAXJA. The other forum was the one I first found when I bought the xj. But, kind of a bad vibe over there now.

Any input would be appreciated.
clutchmasterbreak1.jpg
clutchmasterbreak2.jpg
 
Mine is an 85, and it is all metal, no plastic on the rod end. Check RockAuto.com and see if they have a better brand with no plastic for your year.

I had recent problems with mine that was due to a rusted and weak firewall that was moving when I pressed the clutch, putting severe stresses on the hardware it was not designed for. I had to do a custom repair on the firewall and a welding repair on the clutch peddle hardware to fix mine. Also mine has a metal line not nylon, but has a short rubber hose assy at the slave cylinder (SC) end.

I found that manually pulling the rod back into the slave all the way, after each bleed stroke of the Master Cylinder (MC) was needed to get all the air out of the SC (it tends to have a blind air pocket that refuses to purge)!!! Two man job, and had all the air out in 2-3 minutes.
 
The clutch (brake) fluid (leaks) eats paint and then the firewall can rust, so check your firewall, and the fuse box under the MC (they take a nasty corrosive hit too when the MC leaks out the back seals). And check the peddle mounting hardware for any looseness or damage that is putting a sideways force on that plastic shaft to break it!!!

I just checked Rock auto, all of the plastic.

http://www.rockauto.com/catalog/x,carcode,1180178,parttype,1996

So I would look for worn parts, sleeve-bearing area, loosing bracing, bolts, in the peddle assembly and firewall area. I do not know if the bolt patterns are the same, but you might look to see if the old style MCs could swap.
 
Ecomike said:
Mine is an 85, and it is all metal, no plastic on the rod end. Check RockAuto.com and see if they have a better brand with no plastic for your year.

I had recent problems with mine that was due to a rusted and weak firewall that was moving when I pressed the clutch, putting severe stresses on the hardware it was not designed for. I had to do a custom repair on the firewall and a welding repair on the clutch peddle hardware to fix mine. Also mine has a metal line not nylon, but has a short rubber hose assy at the slave cylinder (SC) end.

I found that manually pulling the rod back into the slave all the way, after each bleed stroke of the Master Cylinder (MC) was needed to get all the air out of the SC (it tends to have a blind air pocket that refuses to purge)!!! Two man job, and had all the air out in 2-3 minutes.
Click to expand...

Thanks for the input. I've searched a fair amount and everything I've found has the plastic end at the stud attachment to the clutch pedal assembly. The '90 master cylinder has an all metal rod and I may look further into that but that would have been for the BA-10 tranny I believe - not sure about the fluid volume on that one or the connecting ends.

I've looked for problems in the footwell. There's no rust on the pedal assembly. I thought there might have been some rust on the stud and that was causing the thing to grab/grind at that point, but it's smooth.

There is some, but very slight, deflection on the firewall where the mc bolts to the body. The thing is I've had no leaks from the cylinder. I'd read the horror stories about the fluid leaking onto the fuse box. Haven't had that, thankfully. It could be the firewall weakness you described. I'm going to take a closer look at that.

Also plan to get rid of the nylon hydraulic line. Called around and looks like about $50 to fab up a braided stainless line with new end fittings. I'll have to tap the aluminum for a fitting, but the write up I saw looked like it should work.

Thanks for the help.
 
There should be 2 bar support brackets on each side under the dash to reinforce the firewall mount on yours. Is one missing? Mine was either missing or it was added in later years.

Here is a link to my repair thread:

http://www.naxja.org/forum/showthread.php?t=1083950

If you can mount the 1990 MC and get the rod length right, I don't the fluid volume is even an issue. I don't think the MC, SC and hose in between will care one bit about the modification. Mine is an 85 Jeep MC and Nissan Transmission SC, as my drivetrain is a Nissan diesel transplant.

The issue would be rod length and the opening that fits over the peddle rod.

You might try reinforcing the plastic with a metal cover or sleeve where it is breaking? Or make/fab a threaded metal end? You could start with a metal female coupling and build on the other end what you need? A welder could fab the part pretty easy I think.

Note the fresh weld in the photo on my thread, that is the other place where my clutch peddle assy got weak and finally failed!!!! I got a weld repair on it that has held so far. Reinforced it some. Check yours with a fine tooth comb, as I missed mine tell it just bent 45 degrees one day!!!!! And that was before the firewall gave out. Scary!!!!
 
My son had problems with his '96 breaking master cylinders, and the problem turned out to be a bad weld and subsequent bend in the arm on the clutch pedal that pushes on the master cylinder. I have posted on this before and a search might turn up a picture of what the thing is supposed to look like. Anyway, if the weld goes bad and or the arm bends a little, it does not push straight on the rod, and two things happen. The MC wears badly in its bore and fails early, and the eye on the end breaks. It's worth looking at that pedal. The arm that operates the MC should be entirely parallel to the pedal shank. If not, it's bad.

It's possible that if you have deflection on the firewall you're getting crooked action that way. I would seriously consider reinforcing that.

I never had any hydraulic problems with the plastic parts on either of my AX 15's, each with well over a quarter million miles, though both mine had external slaves. Those are very easy to bleed because the slave displaces enough fluid to clear the line. But I don't think the plastic lines are a particularly weak spot if the rest of the system is working properly.
 
That is the same part and weld on my 85 that let go, and that I had to get reinforced and rewelded. Then 4 weeks later I discovered the firewall cracks that I had reinforce. Great description, he should follow your advise!!! I agree, X2!

Matthew Currie said:
My son had problems with his '96 breaking master cylinders, and the problem turned out to be a bad weld and subsequent bend in the arm on the clutch pedal that pushes on the master cylinder. I have posted on this before and a search might turn up a picture of what the thing is supposed to look like. Anyway, if the weld goes bad and or the arm bends a little, it does not push straight on the rod, and two things happen. The MC wears badly in its bore and fails early, and the eye on the end breaks. It's worth looking at that pedal. The arm that operates the MC should be entirely parallel to the pedal shank. If not, it's bad.

It's possible that if you have deflection on the firewall you're getting crooked action that way. I would seriously consider reinforcing that.

I never had any hydraulic problems with the plastic parts on either of my AX 15's, each with well over a quarter million miles, though both mine had external slaves. Those are very easy to bleed because the slave displaces enough fluid to clear the line. But I don't think the plastic lines are a particularly weak spot if the rest of the system is working properly.
Click to expand...
 
 
Ecomike and MatthewCurrie:

Thank you both for the guidance here. And, thank you for the photo link. I had never seen a photo of the pedal assembly to compare it to mine. I'd looked at the JY but there seem to be very few with the AX-15 out here. I've looked at probably 20 xj junk yard specimens and there was only one with that was a manual transmission and it had been stripped of virtually the entire drivetrain. That one photo of the pedal assembly helps a great deal, as does the other associated information.

I think that pedal push arm may be a bit out of alignment - and probably failing - and that may very well be the problem. Never even considered that what you would consider to be the strongest piece of the assembly was out of whack.

You guys made my day! I'll report back when I can pull that pedal and get a good look at it in a couple of days, holidays have me jammed up.

Merry Christmas
 
I forget if that era used a bolted setup or a stud with a clip/pin through the end - is there any way you could have the pushrod on the master turned 180 from where it's supposed to be, so it is at a funky angle and/or hitting something during pedal travel? Is there any way you could have it on the wrong side of the clutch pedal arm? I doubt it's on the wrong side as I think a 93 would have a stud on the pedal arm with a clip or pin through the end retaining the pushrod, but there's a slight chance you have the pushrod turned 180 maybe?
 
kastein said:
I forget if that era used a bolted setup or a stud with a clip/pin through the end - is there any way you could have the pushrod on the master turned 180 from where it's supposed to be, so it is at a funky angle and/or hitting something during pedal travel? Is there any way you could have it on the wrong side of the clutch pedal arm? I doubt it's on the wrong side as I think a 93 would have a stud on the pedal arm with a clip or pin through the end retaining the pushrod, but there's a slight chance you have the pushrod turned 180 maybe?
Click to expand...

Thanks for the input here. I've got it figured out now (will post below) but you can't seat it "turned 180 degrees", but it was a good thought and worth checking. The way that it's molded it will only seat one way. There are molded stops, that may strengthen it actually, that won't allow it to fit against the pivot arm. You can see it in one of the photo links Ecomike posted above. Mine was attached just as the photo shows.

Thanks for you help in trying to figure this out.
 
Ecomike said:
There are several old threads on this and the first one has a perfect picture of the final stage when it breaks!!!!

http://www.naxja.org/forum/showthread.php?t=926445&highlight=master+cylinder+clutch

More:

http://www.naxja.org/forum/showthread.php?t=1076849&highlight=master+cylinder+clutch

One good picture in that one.

http://www.naxja.org/forum/showthread.php?t=1054440&highlight=master+cylinder+clutch

http://www.naxja.org/forum/showthread.php?t=1054440&highlight=master+cylinder+clutch&page=2

A 92 with the same problem:

http://www.naxja.org/forum/showthread.php?t=975486&highlight=master+cylinder+clutch
Click to expand...

Ok, Ecomike had it right Thanks for putting me on the right path with this aggravating problem.

Mine didn't break, which actually would have helped, it bent (photos attached) and the problem is that I couldn't tell really. I'm sure that it would have eventually broken. The pivot arm was bent slightly, maybe 1/4 inch and that threw the geometry out of alignment and ate up a few clutch master cylinders. It was hard to see, working upside down in the footwell that it was misaligned.

As you can see in the photos (hopefully) the arm bent slightly at the first "s" working down from the point that bolt slides threw. You can see the upward angle (not parallel to the pedal arm) of the stud that the master cylinder attaches to. You can barely see some hairline cracks where the metal had fatigued also.

I don't think it can be strengthened with a weld at that bend - just wouldn't trust it anyway. Plan is to replace the clutch pedal assembly.

Many thanks to everyone on this post who provided guidance on this.

clutchpedal2.jpg


clutchpedal3.jpg
 
:cheers:
 
Yikes! Looks like you need a new pedal arm that's for sure...

Yeah, I wasn't sure if the pushrod could go on backwards. Glad to hear it can't, though it would have been an easier/cheaper fix I guess.
 
kastein said:
Yikes! Looks like you need a new pedal arm that's for sure...

Yeah, I wasn't sure if the pushrod could go on backwards. Glad to hear it can't, though it would have been an easier/cheaper fix I guess.
Click to expand...

Mine was totally snapped off. I found a talented automotive shop ... welder working on Christmas eve last year that fixed mine for $20. Got about 6,000 miles on it since then. On my 87 XJ.
 
You could put it in a vise and heat it with a torch--should be able to bend it back straight that way without messing up the weld.

Could weld in a couple pieces of metal to reinforce that bend.

Good luck.
 
joe_peters said:
You could put it in a vise and heat it with a torch--should be able to bend it back straight that way without messing up the weld.

Could weld in a couple pieces of metal to reinforce that bend.

Good luck.
Click to expand...

Yep. I did not have to reinforce mine, but it would be easy to do. The OEM set up only had one small inadequite weld on them. Once the weld cracked, the thin weak spot cracked, and then it started to bend easily. It was easy to straighten (I had a pro welder do mine, as that is one of the arts I have not taken the time to master yet). He extended the weld to 3 larger spot welds IIRC. It is holding very well.
 
The back-up plan was to heat it, bend it, and try to weld a bead in the curve with the fatigued metal. Thought I was going to have to do that but was able to locate a clutch/brake pedal assembly out of a '94 from a guy fairly close to me that has about 9 xj's he's parting out. Went to two JY and there wasn't a newer manual tranny jeep in either of them. There were two, an '89 and a '90, but the pedal assembly was different in those years.

Anyway, got the pedal cleaned up and installed. Seems to be working fine now.

But, you know the feeling, I won't be able to trust it for a month!
 
Well that confirms a question I had about possibly using a later year one on my 85.
 
DarrellXJ said:
The back-up plan was to heat it, bend it, and try to weld a bead in the curve with the fatigued metal. Thought I was going to have to do that but was able to locate a clutch/brake pedal assembly out of a '94 from a guy fairly close to me that has about 9 xj's he's parting out. Went to two JY and there wasn't a newer manual tranny jeep in either of them. There were two, an '89 and a '90, but the pedal assembly was different in those years.

Anyway, got the pedal cleaned up and installed. Seems to be working fine now.

But, you know the feeling, I won't be able to trust it for a month!
Click to expand...








My 95 is gone gone gone, but as I recall, there's nothing in the way that would prevent you from simply putting a sheet metal or other bridge between the two arms. Later models (my 99 for sure, and I'm guessing 97 up) did away with the second arm and drive the pushrod off the single main arm.
 
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