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When I do the clutch fluid bleeding to my Nissan Maxima 96, I can push the fluid out of the slave valve. However, I don't see any fluid move from the reservoir into the master cylinder when I press and lift the clutch pedal many time.

How come the master cylinder will not suck fluid from the reservoir? By the way, the reason I bled my clutch hydraulic system is because the clutch becomes soft when I start the car with cold. After 5-10 minutes the car running, the clutch pedal becomes normal.

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    My advice would be just to buy a brake bleeder and just bleed directly from the bleeder valve. It's much easier, more consistent, and less prone to mistakes. If you want to do it without the tool for the job, I can't remember the process at the moment, but I believe you have to: 1. Crack open the bleeder on the clutch (slave?) cylinder. 2. Push in clutch, it should stay down to the floor. 3. Close bleeder valve. 4. Pull pedal out. 5. Repeat.
    – finleyarcher
    Feb 22, 2018 at 2:18
  • @finleyarcher I find that pushing the pedal down, then releasing the valve : letting the fluid out under pressure (safety here - pipe goggles etc), closing valve, letting pedal come up then repeat is more effective...
    – Solar Mike
    Feb 22, 2018 at 7:38
  • @SolarMike probably depends on the car and positioning of the slave vs the master cylinder, but that means the basics of what I stated is right.
    – finleyarcher
    Feb 23, 2018 at 2:57
  • Pushing the pedal down will pump fluid out of through the bleeder while open, lifting the pedal up with the bleeder closed creates the negative pressure needed and prevents air from getting right back into the system.
    – finleyarcher
    Feb 23, 2018 at 2:59

1 Answer 1

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Start with some basic tests/troubleshooting.

  1. Verify that your clutch master cylinder (located driver's side under the dash usually mounting against the clutch pedal) is not leaking.
  2. Verify that your clutch slave cylinder (it will be mounted on the transmission) is not leaking.
  3. Verify all lines between are not leaking.
  4. If there are no fluid leaks at the master cylinder, no swirl or bubbles in the clutch reservoir, and the clutch pedal does not slowly descend with constant pressure, then the master cylinder is likely working properly.
  5. If there is still softness in the clutch pedal, you likely need to bleed it again. As advised above, you should just go get a cheap brake bleeder, it will make bleeding it much easier.

IF the Slave Cylinder or any of the lines are leaking, they have to be replaced.

Tips: Don't let the clutch reservoir run out of hydraulic fluid. If you don't want to spend the $20 on a brake bleeder, get a friend and do the procedure below to bleed the clutch.

  1. Check the fluid level in the reservoir. Fill it to max.
  2. Locate the bleeder screw on the slave cylinder.
  3. Attach an appropriately sized tube to the bleed screw to redirect the hydraulic fluid so it doesn't spray everywhere. This can be fed into a bucket, empty bottle, or whatever.
  4. Open the bleeder screw on the slave cylinder.
  5. Have friend press the clutch pedal in and hold it.
  6. Close the bleeder screw.
  7. Have friend release the clutch pedal (if it sticks, have them pull it up).
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  • Thank you very much, finleyarcher. I just did as you mentioned above 1-7 steps. In step 1, "Check the fluid level in the master cylinder. Fill it to max." Do you mean in the reservior? not the master cyliner? I can not see the fluid level inside the master cylinder.
    – RonYe
    Feb 23, 2018 at 16:58
  • Every time I press the pedal, I open the bleeder and see fluid and air come out the bleeder. Close the bleeder then, release the padal, I expect the master cylinder will suck fluid from the reservior because inside the master cylinder it is in negative pressure condition. But I never see any fluid sucked into the master cylinder. So, continuing this process, without any supplemental fluid from the reservior, the inside fluid will be less and less. So, my problem is: Why the reservior fluid can not be sucked in? The master cylinder is not working? Thank you. Ron
    – RonYe
    Feb 23, 2018 at 16:59
  • @RonYe yes the reservoir not the master cylinder, sorry for being unclear. I will edit to fix.
    – finleyarcher
    Feb 23, 2018 at 21:46
  • @RonYe did you do the troubleshooting first? You probably either have a leak or need to replace both cylinders.
    – finleyarcher
    Feb 23, 2018 at 21:47
  • Also, worth noting, if the master cylinder and slave cylinder are original.. they are probably both leaking. You have a 22-ish year old car.
    – finleyarcher
    Feb 23, 2018 at 21:48

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