Hydraulic Clutch Problem

1980-1986 Datsun 720 forums. All 720-specific topics and discussion can be found here.
lukemeiers
Posts: 10
Joined: Mon Sep 06, 2010 7:07 pm
Car: Datsun B720

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I had a problem with no pressure on the clutch when I pressed on it. Not knowing what exactly to do I dropped the transmission and installed a new clutch kit (pressure plate, clutch plate, throwout bearing). After doing this I tried the clutch, still nothing. So I installed a new master and slave cylinder (under $30 for the two). It took many many pumps to start to feel anything on the clutch. I've tried to bleed as much air as possible out of the system. Air keeps coming and I still get no clutch. The slave cylinder piston won't move the clutch arm at all. In the directions for the slave cylinder it tells me to push the piston into the cylinder until I release the retaining band(s)? Not knowing what or how to do this I simply pushed the piston into the cylinder and kept it in place with the rubber boot that came with it. Any suggestions? Could my clutch arm/throwout bearing be binding up with my transmission shaft so much that the slave cylinder won't push on it? I greased it up and it slid (not real freely) before installation. Any suggestions?


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PEZi
Posts: 20441
Joined: Thu Dec 11, 2008 8:21 am
Car: Mitsubishi Lancer Evolution IX Mitsubishi Racing Edition
Location: Pikes Peak, CO
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sounds to me like you just need a proper bench bleed of the master cyl.... could be wrong though

lukemeiers
Posts: 10
Joined: Mon Sep 06, 2010 7:07 pm
Car: Datsun B720

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I forgot to mention that. I put a new master cylinder on. Also, the transmission turns when I have it in nuetral. From what I was told the slave cylinder should have more force to push on the clutch lever than my hand. I can prevent the slave cylinder from pushing out with my palm. I thought it would have more pressure than that. Any suggestions?

flinterman2000
Posts: 1011
Joined: Mon May 04, 2009 5:32 pm
Car: 2000 Nissan Wingroad, 85 Datsun 720 Pick Up.

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Sometimes you need to keep bleeding to get it right. I'm not a big fan of bench bleeding but its necessary to make sure the master cylinder is working before installation. Keep bleeding it should help.

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brianzero
Posts: 53
Joined: Wed Feb 03, 2010 6:43 am
Car: 1986 Nissan 720 4x4 Regular Cab 265,000 mi! (Gasser unfortunately)

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You need a vacuum bleed pump! You can get them for 20$ at a parts store. This device will change your whole bleeding experience.

Go to Sears and get this:

http://tinyurl.com/22m6abk

flinterman2000
Posts: 1011
Joined: Mon May 04, 2009 5:32 pm
Car: 2000 Nissan Wingroad, 85 Datsun 720 Pick Up.

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Gotta order that vacuum kit. Thanks brianzero.

lukemeiers
Posts: 10
Joined: Mon Sep 06, 2010 7:07 pm
Car: Datsun B720

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Finally got the clutch problem taken care of thanks to my ol' Dad. He got under there and started pushed on the clutch arm in order to push back on the slave cylinder piston. He must've got the seal into place just right. Then he continued to do that to bleed air out of the slave while I intermittently pushed on the clutch pedal. Slowly but surely the piston came out just in time for me to take a 3 hour road trip with no muffler. (Ear plugs).

flinterman2000
Posts: 1011
Joined: Mon May 04, 2009 5:32 pm
Car: 2000 Nissan Wingroad, 85 Datsun 720 Pick Up.

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He had to push in the slave piston? Was it a new slave? Even if it wasn't the fork should have pushed it in. But it works great now so no harm.


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