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355 Clutch slave fluid loss?

Discussion in '348/355' started by Carmellini, Jan 15, 2021.

  1. Carmellini

    Carmellini Formula Junior

    Jul 16, 2019
    440
    I have been reading many previous threads, but I need some folks to explain it to me like I was a three year old. I don't understand the 355 clutch system???

    Today I suddenly lost my clutch pedal. For a moment, it felt like I might be able to pump it up and recover function, but that was quickly dispelled. There was a melon sized puddle of brake fluid under the clutch pumpkin.

    My gut told me my slave cylinder must have given out and on the tow ride home, I thought about removing the external slave, bleeding the system and getting back on the road in a few hours. LOL......

    Where is the clutch slave? Is it part of the throw out bearing? How is it fed fluid? I am lost....

    I removed the pumpkin and my flywheel, disc, and pressure plate look great. Prior to the pedal dump, my clutch was working fine, and felt fine.

    What do I need to replace? Are the Hill Engineering upgrades worth it? My pedal loss and fluid loss came upon in an instant....Is this normal? I would have thought it would have started with a few drops on the garage floor, but this was a sudden failure. Some threads speak of parts that are prone to cracking? what parts?

    Lot of questions and I hope there are others who are equally confused and this thread can create some clarity.
     
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  3. m.stojanovic

    m.stojanovic Formula 3
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    Dec 22, 2011
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    It is fairly simple actually. The slave cylinder is concentric, sitting behind the throw-out bearing (see this video: ).

    Some slave cylinders are made of aluminium and are known to crack = sudden loss of fluid. Hill Engineering one is superior. This is the slave on my 348 (cast iron body); below is the Hill Eng kit:

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  4. marioz

    marioz Formula 3

    Nov 21, 2003
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  5. Carmellini

    Carmellini Formula Junior

    Jul 16, 2019
    440
    Uh huh...great video and great explanation. Thank you, Miro. I have only been familiar with old school external slave activating a fork.

    It appears that fluid is fed thru the flange? So does the flange act as the slave? Or is the slave part of the release bearing?

    My transmission number is 168372 and my serial number is 2535, the earlier style.

    Would mine be cast iron as well?
     
  6. Carmellini

    Carmellini Formula Junior

    Jul 16, 2019
    440
    Do you know your transmission number? early or later? Is the housing part of the flange?
     
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  8. steved033

    steved033 F1 Rookie
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    Apr 12, 2017
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    should he do triple seals while he's in there?? wink wink..

    This is the shaft in the shaft I was talking about. the inner is the blue arrow, the outer coarse spline drives the transmission.

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    The shaft pulls out (get that o-ring too):

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    There are tutorials on how to push the seals on and get them to seat without slicing them on the splines. (It's a huge pain).

    sjd
     
  9. marioz

    marioz Formula 3

    Nov 21, 2003
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  10. steved033

    steved033 F1 Rookie
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  11. marioz

    marioz Formula 3

    Nov 21, 2003
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    I bought my CRB355MS release Brg. plus some seals from Ricambi for a total of $611.95 including freight in 2014.
     
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  13. yelcab

    yelcab F1 World Champ
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    Nov 29, 2001
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    Mitchell Le
    Buy the viton triple seals from Superformance, it makes the job immensely easier. None of the heat it up, boil it, slide it on using an big socket, squeeze it back down with a hose clamp - nonsense - I always have a set sitting in my shop.
     
  14. Ricambi America

    Ricambi America F1 World Champ
    Sponsor Owner

    The most common replacement we seem to see is the CRB348/F355 kit (bearing, flange, seals). We have the OEM version of the triple seals 137249 if you want to go that route. They don't necessarily always get replaced alongside the release bearing/flange stuff, but I certainly can't find any compelling reason to not do it 'while you're in there'

    As @yelcab notes, there are other options for the seals if you prefer a different material.
     
  15. johnk...

    johnk... F1 Veteran
    Owner

    Jun 11, 2004
    8,491
    New England/FL
    Devils advocate here. I can think of a compelling reason not to. Get it wrong, do it twice (or more). Don't do the job, no reason to suspect it will mysteriously start leaking. Of course, everyone knows I'm a don't fix what ain't broke guy., not to mention, old and grumpy. :)

    But if you are going to "while you are in there", why not replace the clutch and pressure plate, and how about resurfacing and repacking the flywheel. And that starter motor is at least 21 year sold now. :D
     
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  16. Carmellini

    Carmellini Formula Junior

    Jul 16, 2019
    440
    Chicken, or the egg????? First thing I noticed is a broken spring:

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    Next was this:

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    My trans number 168372/2535 is the early style, but my spring hole measurement is 86mm? Guessing flange and bearing were replaced before?

    Do I need a complete kit, or just the bearing and springs?
     
  17. 348Jeff

    348Jeff Formula 3
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  18. Carmellini

    Carmellini Formula Junior

    Jul 16, 2019
    440
    That would be nice.

    Is the flange upgrade only necessary if you DO NOT have the 86mm spring spacing?
    any other benefit to adding the Hill Engineering flange?
     
  19. Ricambi America

    Ricambi America F1 World Champ
    Sponsor Owner

    If you have 86mm spring spacing, and the flange isn't scored, chipped or damaged, you don't need a new one.
     
  20. m.stojanovic

    m.stojanovic Formula 3
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    Yes, the fluid is fed through the flange and the flange also acts as the slave piston (fixed). The slave cylinder is the body with seals inside and, instead of the piston moving, the cylinder moves over the piston (flange). The thrust bearing is attached (pressed) onto the cylinder body.

    You will notice that the flange has a step, a transition from bigger to smaller diameter, and the cylinder has a suitable larger and smaller inner diameters and seals. This difference in piston (flange) diameters enables the fluid pressure to push the cylinder towards the piston area with smaller diameter. The larger inner diameter area of the cylinder moves over the smaller piston diameter and the gap between the two is filled with fluid under pressure.

    The two springs hold the cylinder and the thrust bearing constantly in contact with the pressure plate diaphragm "fingers" with some light pressure.
     
  21. Carmellini

    Carmellini Formula Junior

    Jul 16, 2019
    440
    ^^^^^^^^ great explanation......I finally understand.......thank you

    great news order placed
     
  22. Carmellini

    Carmellini Formula Junior

    Jul 16, 2019
    440
    Debating about the triple seals....are there any Viton suppliers in the US? Not excited about waiting a few weeks.

    The inside of my pilot bearing is wet or moist with gear oil. Does gear oil weep thru the small hole in the shaft,
    or does that wetness indicate passing thru the triple seals? It nearly negligible, but thought I would ask.
     
  23. m.stojanovic

    m.stojanovic Formula 3
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  24. Carmellini

    Carmellini Formula Junior

    Jul 16, 2019
    440
    New Hill bearing installed with new springs and new Viton seals. (Thanks Mitchell). Viton seals went on very easy in about 5 minutes total; no issues and highly recommend. Complete job was very simple and straight forward. I am used to working on older cars and was not aware of this design; ingenious.

    Here is what my old seals looked like. Feel like plastic with no elasticity. Thanks for everyone for the help and guidance.


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