Bench bleeding clutch master cylinder.

Posted by xtalontsix, Aug 29, 2011
Maintenance & Repairs - Oil choices, timing belt, setting timing, CV boot replacement, alternator servicing, fuse/relay checks, and other basic maintenance, repair and diagnosis discussions.

  1. xtalontsix

    xtalontsix Probationary Member

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    Eagle River, Wisconsin
    I recently replaced the master cylinder in my car because it had very little pedal pressure and was leaking some fluid under the dash. I did not bench bleed the new master cyl i just bled the whole system at the slave cyl. Two days after replacing it, it started to grind when selecting a gear so i bled the system again and it was good for a few more days. On the way to class this morning everything was fine then i left for lunch. Now i can hardly get it into gear and there is a awful grinding when selecting gears. If i shut the car off it shifts fine, if i start it in gear with the clutch in the car lurches forward. Ive read as many threads as i could about bench bleading but never got a straight answer. Im just wondering if the proper way is to bench bleed it first or could i just power bleed from the slave.
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  2. XiKeiyaZI

    XiKeiyaZI Supporting Member

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  3. GsxEcutioner

    GsxEcutioner Proven Member

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    I was told to jack the car up on the passenger side so that the air bubbles will move and re bleed from the slave. it worked for me.
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  4. LiquidX

    LiquidX DSM Wiseman

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    If you are getting air in the system then you have a hole somewhere and it needs to be fixed. You made sure to keep the fluid level topped off when you did the bleed and you bled it into a container with fluid in it correct? If all else fails, get a speed bleeder nipple. I would also double check the line connections to the master cylinder and slave.
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  5. galantlvr34

    galantlvr34 Proven Member

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    You might have to adjust the rod more on the master cylinder if you are sure all the air is out of the system.When you push in the slave cylinder in with your hand does it come back out?
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  6. LiquidX

    LiquidX DSM Wiseman

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    Expanding with a video.

    <iframe width="420" height="345" src="http://www.youtube.com/embed/vYJxQyjIhUw" frameborder="0" allowfullscreen></iframe>
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  7. DSM1G90

    DSM1G90 Supporting Member

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    With that new master, true, the rod have to be adjusted due to the valve inside.

    did you replace the slave? usually it's a good idea to replace both. For the slave could have a bad gasket seal around the piston - why you're losing pressure.

    Crawl underneath and lift the boot away from the slave case. See fluid..slave is shot.

    I have an old fashion way to bleed: open up the spit on the slave and let the old fluid pour out and chase behind with new fluid. Close the spit and fill the fluid bottle full. Then open up the spit for a bit to get a good stream of fluid, then close the spit. Fill the bottle full again.

    Now, grab a buddy (or like with me, get the wife to help me) and have them sit in the driver's seat. I tell them to pump up the pedal until the pedal has pressure behind it, then hold it down tight. I tell them when I open up the spit, that pedal is gonna collapse and NOT TO LET THE FOOT off the PEDAL, for if they do, I have to do it all over again.

    I open the spit, "spoosh" a shot of fluid comes out and the pedal is mashed to the floor. I close the spit and tell them to pump up that pedal to pressure again..and then HOLD IT. I open up the spit, "spoosh!" another shot of fluid comes out. I close the spit and have them pump up the pedal. This time I can see the slave being activated with the pedal pressure... "Dang, got the thing bled good!"

    Works every time ... and I do the same with brakes.

    Okey, so I'm old....but...been there and done that a few too many times...and it works every time.

    -DSM
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