slave cylinder autopsy

jvandyke

jvandyke

True Classic
newer slave failed recently, piston so loose I could easily shake it out.
Swapped in the old one, it too failed recently. Both bores looks good.
"old" one had rusty crap in it, the newer one's bore looks pristine, the pistons are very different though.
I ordered some seals from Fiatsplus, thinking of putting new seal on older piston as it seems "rebuildable".
Remove clip, spring old seal, replace, redo. The "outer" seal is less critical I would think, just a dirt stopper? I can always buy a new slave as they are cheap enough but it's kinda interesting.
old slave (note crud)
SDC12079_zpsce150486.jpg

old piston, note clip and spring
SDC12083_zps657e6527.jpg

"newer" slave
SDC12086_zps4d575047.jpg

"newer" piston
SDC12084_zps32750daa.jpg

page from manual, that matches my "older" one, better? just different? hmmmm
slaveguts_zps408e66a9.jpg
 
Is the bore larger on the newer one? If so it would likely have somewhat less throw.

The older one is a better design, I would rebuild it. The new one relies on a "leaf" seal which will wear faster than the solid compressed seal of the original Fiat type design.

I used to carry a set of new seals in an envelope in the glove box. It came in handy when I was driving from LA to VT and it failed overnight in Kansas.
 
Yep, bore is the same. I think the OEM design is better too. Hopefully the seals I ordered from Obert fit. Hard to come by although there's probably many that will work. 3/4" OD, ID is actually really sloppy (by design I imagine) to allow the seal to "float" a bit. Planning on "new" cylinder with OEM piston with new main seal. No sense buying another new slave with weaker seal design. Be nice to find a source of adequate seals that work as I think rebuilding these not only gives you better long term reliability but is a lot cheaper too.:) I think the bore of the original slave is salvageable too. I'll shoot it with fogging oil and throw it in a plastic bag and dump it in the parts bin. I think the replacement slave is lighter, FWIW probably not built quite to the same specs as OEM. Like many things.
 
Got seals today, wrong ones though.
Here's what I got:
file_zps7a0d6c42.jpg

Not like the picture here at all, part numbers match.
Not quite like pictured. Looks like I got the outer seal, the "dirt or dust seal" not the main one. Bummer. Shoulda just got another new slave I guess.
So I'm thinking the "main seal" on the master is the same as that on the slave (probably the brake master too?). I pulled the seal from my old clutch master and it looks identical to the slave's seal.
Kinda needed the car tomorrow.
Had a slave rebuild kit for a first gen RX7 sitting the bench. Same bore, seal looks very similar, piston is a tad shorter. Might try that piston in the Fiat's slave, or try to swap the seal onto the Fiat's piston. I think ultimately I'll try to find a match in something more available in a rebuild kit and just use those seals.
I know the whole thing is kinda silly when a slave costs $30 but if they crap out then they aren't even worth that. I'd rather be able to rebuild a "good" one for $3 in seals than replace it with a whole crappy slave for $30, no?
Here's the line up:
far left; replacement slave's piston with flimsy "cup seal"
middle RX7's slave piston with beefier version of a cup seal.
right, OEM slave with clip and spring removed, seal laying there, not a "cup" seal, it's solid, original shape unknown as it is probably worn down. On the right is a clutch master piston with "main"? seal removed which looks just like the slave's seal.
file_zps1121913a.jpg
 
That sucks.

I'm with you, I'd prefer to rebuild an original sturdy design, than use a lesser quality new.

I hope you find a replacement seal - so, basically square cut, but perhaps with chamfered edges, it seems.
 
I'm gonna try the Mazda's whole piston, rather than risk trashing the seal getting it off. It's a tad shorter, not sure if that will matter much, just adjust the rod a bit to compensate? The kit I took it from has a spring and a big gator boot. I won't use the spring but the gator might make a nice dust boot. Part # from kit [ame="http://www.amazon.com/Dorman-CSK351232-Clutch-Slave-Cylinder/dp/B001PYG9Y6"]CSK351232[/ame] for a bunch of Mazdas and Fords. Just put it on and bled it out. Good throw and the gator fits pretty nice, covers the bulk of the slave rod, didn't use the spring, which I assume is meant to fit inside the slave behind the piston. I'm sure there's probably an infinite number of cars running 3/4" bore stuff that has seals that will work. Off to test drive.
 
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Well, it works great, no leaks, good clutch feel. Two test drives and several leak checks and I guess I'm good to go, at least for one day, I think.
 
Fiat seal is square with a tapered edge (if that's the correct terminology) The one from the kit, the "mazda" one (I don't remember which car I bought it for, pretty sure it was for the RX7) is more of a cup seal but it's noticeably thicker and stiffer than the aftermarket Fiat one. I know my old Midget has a 3/4" bore brake master, don't know clutch master or slave off the top of my head but many were 7/8" bore too. I'm thinking it's better to find a cheap supply of seals and rebuild then buy replacement slaves that are known to fail early, apparently seals marketed for our slaves are non existent but there's hundreds that will work fine. It does seem the seals for the masters are the same as the slave. The long gator is nice over the slave rod too.

MG, from what I remember none of the Midget's (or Bs) used 3/4" bore slaves, they were either 7/8" or 1". There was a brief period where the Midget's used a 3/4" bore master, the 1098 with disc brakes (the car I had) those masters are unobtanium to the nth degree (ask me how I know) but rebuild kits exist so, in theory, you could use those seals, not knowing exactly how those seals compare but if anyone knows of any "common" car that ran 3/4" bore brake/clutch/slave/master, those rebuild kits could yield some useable seals, such kits can go for $4 and you sometimes get two seals. I'll keep looking around but at least the kit I just happen to have sitting on my bench (literally RIGHT next to my pile of X clutch slave bits) yielded a viable seal. (after paying "big" money and waiting for the wrong ones). Come to think of it, I probably have a couple kits for my Midget, and for my Opel, heck I could have 10 seals sitting in my pile.
 
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Here's another similar kit, (CSK1232) boot looks a little shorter, same bore? (3/4" OD on the seal is what we want). If you can order up from a local parts shop, NAPA or whatever, no shipping and in hand for $10 or so probably. I'd rather find one with loose seals (don't really need the piston) so can easily replace the OEM piston's seal. Rock auto lists for $4 but shipping probably has you back to $8, still pretty darn cheap.
 
I've just fitted a new clutch master and slave to mine. I'll report back if it fails. I hope not. I've only just got a really nice feeling clutch peddle.
 
I think the replacements are inferior across the board, cheaper metal, different design, fewer parts, flimsier. Depends on source maybe. If you only drive it a few thousand a year might last a while. Mine went 10,000 or so, I think.
 
jvandyke said:
Got seals today, wrong ones though.
Here's what I got:
file_zps7a0d6c42.jpg

Not like the picture here at all, part numbers match.
Not quite like pictured. Looks like I got the outer seal, the "dirt or dust seal" not the main one. Bummer. Shoulda just got another new slave I guess.
So I'm thinking the "main seal" on the master is the same as that on the slave (probably the brake master too?). I pulled the seal from my old clutch master and it looks identical to the slave's seal.
Kinda needed the car tomorrow.
Had a slave rebuild kit for a first gen RX7 sitting the bench. Same bore, seal looks very similar, piston is a tad shorter. Might try that piston in the Fiat's slave, or try to swap the seal onto the Fiat's piston. I think ultimately I'll try to find a match in something more available in a rebuild kit and just use those seals.
I know the whole thing is kinda silly when a slave costs $30 but if they crap out then they aren't even worth that. I'd rather be able to rebuild a "good" one for $3 in seals than replace it with a whole crappy slave for $30, no?
Here's the line up:
far left; replacement slave's piston with flimsy "cup seal"
middle RX7's slave piston with beefier version of a cup seal.
right, OEM slave with clip and spring removed, seal laying there, not a "cup" seal, it's solid, original shape unknown as it is probably worn down. On the right is a clutch master piston with "main"? seal removed which looks just like the slave's seal.
file_zps1121913a.jpg
Click to expand...

Jeff,
I can only apologize about the picture that was on my web store NOT matching the product in the bag. I have gone thru some receivers that really didn't give a ****, so it's taking some time to clean up what they did. It seems no one cares to do their job "right" for longer than it takes to train them, and then it takes years to find some of the stuff they did wrong.

My web store pictures have been updated to show the two lipped seal that we have under 4184521 http://www.fiatplus.com/3mm-thick-lipped-hyraulic-seal-pr-279520.html . This is the seal you ordered and received.

As long as your goal is replacing the 3 mm wide seal, the currently available one that you got will do the job.

However, when I look at your picture above, on the cylinder guts on the left I see that you seem to have the 6 mm wide seal 792780 http://www.fiatplus.com/6-mm-thick-two-lipped-seal-pr-276543.html off the piston. It seems the 3 mm wide one is still mounted? As you can see, the currently available 6 mm wide seal looks a lot more like the seal you have off. And the 4184521 looks like that seal still mounted.

On the original (?) cylinder guts on the right of the silver guts, I see the 4184521 also is still mounted. On that same cylinder I see it uses the third style of seal 4115451 http://www.fiatplus.com/3-4-hydraulic-cylinder-d-ring-pr-278977.html that was later replaced by 792780.

Your picture of the disassembled master cylinder (guts on the right) looks like you also have the third style of 3/4 inch bore seal off, the one I call a "D" ring 4115451. I just had a major rebuilder take every one I had (I should have more by February 2014), but I still have some kits that have that seal in it.

Let's look at your very first post above, and let's look specifically at the exploded line drawing at the bottom of that post.
jvandyke said:
slaveguts_zps408e66a9.jpg
Click to expand...
Part #8 is 4184251, part #10 is 4115451. 792780 is not shown because that style of seal was not being used in this application when the drawing was done.
Confusing? Yes. Especially when my web store had a incorrect picture posted!


Let me know how I can make what you got, versus what you wanted, correct.

Chris Obert
 
Chris at Fiatplus hooked me up with several more seals that sure look like the right ones. Thanks Fiat Plus!!
I think I'll go with the OEM slave piston (both new seals) in a replacement slave since its bore looks a tad better than the OEM one although the replacement feels lighter.
On the master I'm keeping the replacement bits but with new seals, the masters both look and feel the same but the pistons are a different design, one is noticeably lighter and slightly different as to how the seal is retained; one has a smaller shoulder then uses a washer so swapping seals is easier, don't have to stress the seal so much getting it up and over the shoulder. This looks like the one in manual;
http://xwebforums.com/wiki/images/1/16/WrokshopManual_7.pdf
Wondering about bench testing. Seems like you could hook up the output to a pressure reader of some sort and compress on the bench. Although swapping in and out of the car has become a bit routine. About 30 minutes to get the master out this last time.
 
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