Replacing clutch master cylinder
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Replacing clutch master cylinder
As the tittle states, just looking for what fluid you guys are using. Its been a wile since I've replaced one of these and have never done it on the S. There was no clutch fluid at the auto parts store and I seem to remember that brake fluid is what we use as its the same stuff, so I picked up some Dot 4. Let me know what you guys think. I'm doing the master cylinder swap now. Thanks guys 
Joined: Jan 2006
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From: 17 ft below sea level.
Last time I used a DOT 5.1 brake fluid.
DOT 5.1 fluids are a little thinner when cold so it took a little - but noticable - less effort to press the clutch pedal.
Note: I have an ACT pressure plate.
The FMVSS standard for brake fluids (#116) actually specs a DOT 3 fluid to have a lower max viscosity when cold than a DOT 4 (max 1500 cSt vs max 1800 cSt) while the hot viscosity has the same limit for all fluids (no less than 1.5 cSt @ 100C)
They test the cold viscosity at -40C and that seems way out of normal operation temp but a thinner fluid @-40C will also be thinner at 0C and at 10C and so on.
Again: I noticed it with my clutch pedal.
Right now I'm looking for the "new" ATE SL.6 brake fluid, specially designed for ABS-ESP systems.
Its thin acros the temp range (max 700 cSt @ -40) so the ABS response time is less.
If I can get it I'm going to use it in my clutch and brakes.
ATE SL.6 is a DOT 4 fluid, btw.
DOT 5.1 fluids are a little thinner when cold so it took a little - but noticable - less effort to press the clutch pedal.
Note: I have an ACT pressure plate.
The FMVSS standard for brake fluids (#116) actually specs a DOT 3 fluid to have a lower max viscosity when cold than a DOT 4 (max 1500 cSt vs max 1800 cSt) while the hot viscosity has the same limit for all fluids (no less than 1.5 cSt @ 100C)
They test the cold viscosity at -40C and that seems way out of normal operation temp but a thinner fluid @-40C will also be thinner at 0C and at 10C and so on.
Again: I noticed it with my clutch pedal.
Right now I'm looking for the "new" ATE SL.6 brake fluid, specially designed for ABS-ESP systems.
Its thin acros the temp range (max 700 cSt @ -40) so the ABS response time is less.
If I can get it I'm going to use it in my clutch and brakes.
ATE SL.6 is a DOT 4 fluid, btw.
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^^^ Interesting, thanks for the info. I'm running a SOS sport clutch. Feels the same as stock but 30% more holding capacity for my FI application. The peddle could use some stiffening up as far as I'm concerned so that doesn't bother me. I just want to make sure this Dot 4 I'm putting in will be compatible long term with seals/hoses etc. I don't want to create a problem down the road becuase I picked the wrong fluid. So from what I gathered you agree dot 4 is good to uses as well?
