[Fot] Slave cylinder/master cylinder

[Philip Gott]

That nasty black stuff that accumulates in the master cylinder is small bits of the rubber seals that get worn off during operation. The modern fluids are generally less lubrous than those of the time when these systems were designed.
One wise FOT-er put us into Motul 600 as a good high boiling point brake fluid that also has good lubrication qualities.
For clutches we use the Quartermaster Clutch Hydraulic Fluid. It is VERY slippery and dies the trick for clutch systems. Not intended for brakes, however.
Phil Gott

Sent from my iPhone

> On May 27, 2023, at 7:00 PM, Bob Kramer Gmail <rkramer56 at gmail.com> wrote:
> 
> I don’t know why the fluid in the clutch master cylinders gets nasty so quickly, but it does. I start my CMC bleeding process by sucking out all the old fluid from the reservoir, wiping it out and filling with fresh fluid. I make sure to use all the first fill in the bleeding process so I know all the older fluid has passed out of the slave cylinder. 
> 
> Sent from my iPhone
> 
>> On May 27, 2023, at 1:46 PM, J Wagner via Fot <fot at autox.team.net> wrote:
>> 
>> 
>> 
>> Yes, assuming the seals are sound, as suggested, simple bleeding could be the fix.  Water/Air in the system, expanding with heat,  could be taking up some of the pressure required to release the clutch.  (Think brake fade.)
>> 
>> And how old are the seals in the cylinders?  Maybe the general thermal expansion in the cylinders and/or heated fluid and rubber, is just enough to cause some failure of aging seals?
>> 
>> While it’s messy, and it’s been a while for my 4A, after an initial bleed at the slave to just get the system filled with fresh fluid, I used to bleed the master before a final bleed of the slave, by loosening the line ahead of the slave (with the slave nipple closed) as if it were a bleeding nipple.  (loosen, push, hold, tighten, repeat… clean up fluid as it’s a blind bleed into a rag)  Then do a final bleed at the slave nipple.  That always seemed to make it all go faster, relatively effortless.   (I always thought to make some sort of custom bleed screw between the master and slave, but never did.)  
>> 
>> Between owning British cars, doing my own plumbing for decades, and working water gag special fx in the film buiz, I feel like I should get an honorary PhD in general hydraulics, though, I am quite aware, I still only know .002% about them.  Ok, even less.  
>> 
>> —Justin 
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>>>> On May 27, 2023, at 9:36 AM, Philip Gott via Fot <fot at autox.team.net> wrote:
>>> 
>>> Have you tried bleeding it?
>>> 
>>> Sent from my iPhone
>>> 
>>>>> On May 27, 2023, at 11:16 AM, McKearn McKearn via Fot <fot at autox.team.net> wrote:
>>>> 
>>>> 
>>>> Hi all.
>>>> Got the GT6 out a few days ago and remembered that I was going to fix the clutch problem I had last fall before I stored it away   but did'nt ..
>>>> So long story short, I don't know if it's the slave cyl or master cylinder but it works fine at first few shifts but as you drive it you get less and less clutch movement.
>>>> Seems like if you let it set a while it will work  again..
>>>> Any ideas?
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