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Clutch Cylinders


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Getting ready to replace a couple ,four to be exact, master, slave cylinders on a couple MJ'S. Heard about where guys replaced, repaired their cylinders and they leaked due to inferior seals. I'm looking for recommendations on which brand names, or sources to avoid and which one are OK. Quality comes before price. :thumbsup:

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I think part of the answer with the after-market clutch hydraulics is to ignore the "experts" who say it can't be done, and use DOT-5 silicone brake fluid instead of clutch fluid. I've been running the '88 XJ with silicone in the brakes for over twenty years and in the clutch for about twelve years. No problems yet ...

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I think part of the answer with the after-market clutch hydraulics is to ignore the "experts" who say it can't be done, and use DOT-5 silicone brake fluid instead of clutch fluid. I've been running the '88 XJ with silicone in the brakes for over twenty years and in the clutch for about twelve years. No problems yet ...

DOT-5 is the only thing I been using. Except once when I broke down and lost all the fluid. 70 miles from home, no DOT-5, Filled it with Dexron AT fluid. Got me home, and then some.

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I think part of the answer with the after-market clutch hydraulics is to ignore the "experts" who say it can't be done, and use DOT-5 silicone brake fluid instead of clutch fluid. I've been running the '88 XJ with silicone in the brakes for over twenty years and in the clutch for about twelve years. No problems yet ...

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Good call.

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Unlike DOT3 brake fluid which absorbs moisture out of the air, DOT5 is silicone-based and doesn't. That alone is good enough reason to use it, besides the fact that its boiling point is something like 3 times higher.

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There are 3 problems I see with DOT5. First is the price - the stuff was $32/quart last time I priced it (and it was a while ago).  Next is that you cannot mix it with DOT3 fluid - so any time I am replacing major components I consider changing over to DOT5 (you're supposed to clean the DOT3 out with isopropyl alcohol and compressed air). Last is that it doesn't like fast bleeding. Any rapid agitation in the presence of air will mix tiny bubbles into the fluid, which take months to get out. Best way is to slowly back-bleed with low pressure from the bottom to the top.

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In the MJs (and XJs), another benefit is that it isn't corrosive, so if the master cylinder leaks and fluid bleeds onto the fuse panel, the panel isn't trashed. I think the silicone is also kinder to the rubber in the seals, as well.

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In the MJs (and XJs), another benefit is that it isn't corrosive, so if the master cylinder leaks and fluid bleeds onto the fuse panel, the panel isn't trashed. I think the silicone is also kinder to the rubber in the seals, as well.

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DOT3 brake fluid isn't in itself corrosive - it's the moisture from the air  that DOT3 absorbs that causes the corrosion.  (For that matter, water isn't  itself corrosive,  but rather the dissociated ions  that water picks up in solution that are.) Since DOT5 doesn't absorb moisture, you don't have that problem, which is I think the best reason to use it in a street car.

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DOT3 isn't corrosive to metal. But it will completely dissolve the fuse block.

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Most plastics are safe from brake fluid (it ships in a plastic bottle, after all). Are you saying the plastic fuse block itself will wash away in brake fluid, or just the tar backing?.

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Eagle mentioned corrosiveness - I thought he was referring to the terminals of the fuse block. Anything that is corrosive will by definition carry electric current, so the fuse block terminals are in double jeopardy (as is the surrounding sheetmetal - like the floorpanel  - because it is grounded to the battery). The threat of dissolving the plastic fuse block and having it puddle on the floor makes it triply bad (I had never seen nor heard of this) - quadruply so if you consider the resulting fire risk.

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I guess the  choice of plastic for fuse block plastic was a poor one if it dissolves like paint in contact with brake fluid. I wonder if there is a replacement alternative that would weather DOT3 - and why NHTSA never forced a mandatory safety recall.

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  • 8 months later...

There was an issue from the factory when they used Girling cylinders. 

 

There was also an issue with the HOSE between the master and slave. The fluid they used reacted with the lining of the hose to form an abrasive crystalline substance which would keep taking out cylinders... Unless of course you did as they finally recommended and always replace the original hose. 

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