Nissan 370Z Forum - View Single Post

Fountainhead · 03-18-2017, 09:57 PM

Hi All,
Open the Clutch Master Cylinder reservoir lid and have someone press the clutch in and out and you will see the fluid of the MC reservoir moving as you cycle the clutch. Think about it, where will the volume of fluid pushed into the CSC return to after actuation? The CSC rides against the Clutch fingers and CSC is normally depressed about 50% position. When the clutch pedal is pressed the CSC fully extends and presses the clutch fingers in about ~0.5 to 0.75 in. When the clutch pedal is pressed in and released, the CSC returns to 50% position. The volume of liquid used to increase the CSC position has nowhere else to go but back into the master cylinder. CSC fluid is constantly changing location from the CSC back to the Clutch master cylinder reservoir.

Brakes only travel a fraction of an inch to press the calipers and the volume of liquid moving is far far less, traveling 5x the distance of the Clutch fluid so there is really no noticeable change/fluid volume change in the brake reservoir.

So in short, the Clutch fluid does move around and is not trapped entirely in the CSC.
Brake fluid is trapped at the Caliper cylinder and cannot move back to the Brake master cylinder.

yes I still regularly change my clutch fluid and for 5 years have used DOT 3/4 Valvoline and so far no problems. It's clean as a whistle. I never let it get even slightly dirty.
I usually empty the master, fill it up, pump the pedal about 12 times then empty the master and fill it back up again. I suppose one day I'll bleed the CSC from the bottom but I will only do so to find out if it has foreign bodies *clutch dust* in the bottom. If the video guy had pumped the clutch about 12 times after the initial fluid removal/addition you would have seen the dirty fluid returning to the master reservoir after a few pumps. Honestly mine has never been dirty enough but to barely see the fluid is contaminated, so I doubt mine is dirty down at the CSC.
If it had been black and chunky I would have bled from the bottom. I may still bleed from bottom, and report back here but I expect to see clear fluid.

03-18-2017, 09:57 PM	#15 (permalink)
Fountainhead Track Member Join Date: Feb 2013 Location: FL Posts: 834 Drives: 2019 Civic Type R Rep Power: 14	Hi All, Open the Clutch Master Cylinder reservoir lid and have someone press the clutch in and out and you will see the fluid of the MC reservoir moving as you cycle the clutch. Think about it, where will the volume of fluid pushed into the CSC return to after actuation? The CSC rides against the Clutch fingers and CSC is normally depressed about 50% position. When the clutch pedal is pressed the CSC fully extends and presses the clutch fingers in about ~0.5 to 0.75 in. When the clutch pedal is pressed in and released, the CSC returns to 50% position. The volume of liquid used to increase the CSC position has nowhere else to go but back into the master cylinder. CSC fluid is constantly changing location from the CSC back to the Clutch master cylinder reservoir. Brakes only travel a fraction of an inch to press the calipers and the volume of liquid moving is far far less, traveling 5x the distance of the Clutch fluid so there is really no noticeable change/fluid volume change in the brake reservoir. So in short, the Clutch fluid does move around and is not trapped entirely in the CSC. Brake fluid is trapped at the Caliper cylinder and cannot move back to the Brake master cylinder. yes I still regularly change my clutch fluid and for 5 years have used DOT 3/4 Valvoline and so far no problems. It's clean as a whistle. I never let it get even slightly dirty. I usually empty the master, fill it up, pump the pedal about 12 times then empty the master and fill it back up again. I suppose one day I'll bleed the CSC from the bottom but I will only do so to find out if it has foreign bodies clutch dust in the bottom. If the video guy had pumped the clutch about 12 times after the initial fluid removal/addition you would have seen the dirty fluid returning to the master reservoir after a few pumps. Honestly mine has never been dirty enough but to barely see the fluid is contaminated, so I doubt mine is dirty down at the CSC. If it had been black and chunky I would have bled from the bottom. I may still bleed from bottom, and report back here but I expect to see clear fluid. Last edited by Fountainhead; 03-18-2017 at 10:36 PM.