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clutch slave Bursting


ddrum

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ok, so i just finished overhauling my l20b for my 620, put it in and it starts up amazing! :w00t:

 

Anyway, i decided to install/bleed the slave cylinder to take it for its first drive! and the cylinder exploded leaving fluid everywhere! So i bought a new one and the same thing happened. Got another one since i have lifetime warranty and same thing happened. Changed it one more time and same thing happened. I got under the truck and noticed that when someone pushes the clutch, the slave pushes the fork all the way back and when you let go off the clutch, the slave just gets stuck at the end of the fork not going back. That is why when i keep pumping the clutch, fluid just gets accumulated and makes the slave cylinder burst. :sneaky:

 

Could this be that the slave cylinders are bad out of the box? (Duralast) or that my clutch master is bad? or anything else? :confused:

the clutch is brand new for a 79 620 and i bought the release bearing collar from the dealership also for a 79 620.

 

Thanks, erick

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I guess it could be a slave issue... but having gone through 4 of them should tell you its not that. Unless of course they dont like to be extended that much and then bind on return.

 

Except it is blown already, I would see what the master is doing, Like have the cap off, and watch the fluid level as you pump it.

 

But really, there are only 2 things in the hole hydraulics for the clutch, Master, and slave. Unless you have some odd contraption on the line running between the 2.

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Push down on the clutch peddle with your thumb. There should be a small amount of play before resistance is felt. If no clearance the piston in the master can't return to it's rest position and let the pressure and fluid in the line ahead of it back into the reservoir. If you look up under the dash you'll see the peddle connects to a push rod and there is a way to loosen and adjust it.

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After getting another installed and bleed, push in clutch all the way. Then release pedal,quickly ck slave and see if it reterns all the way. Also try opening bleed screw and see if u have noticible pressure. No pressure, slave piston binding or hanging up. Pressure,master problem likely. In burstimg, what exactly do u mean? Blowing out piston or metal body cracking,ect.?

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After getting another installed and bleed, push in clutch all the way. Then release pedal,quickly ck slave and see if it reterns all the way. Also try opening bleed screw and see if u have noticible pressure. No pressure, slave piston binding or hanging up. Pressure,master problem likely. In burstimg, what exactly do u mean? Blowing out piston or metal body cracking,ect.?

 

it is blowing out the piston and draining through the rubber, it pops out with pressure. like a burst. no craking

 

 

ddrum.... is it possible that you assembled the clutch arm without the release bearing or collar? Can you move the clutch arm back by hand?

 

clutch arm is the clutch fork right? if so yes i did install the collar to the clutch arm correctly with the clip retainer. yes i can move the clutch arm by hand. Could i have done something wrong?

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Yeah it just pops out, I bought a new master cylinder and exchanged my slave cylinder for a new and will be changing them Friday. Hope it works this time if not I'll drop the tranny and see what's going on.

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Well today, i removed the fork boot and moved the clutch fork by hand to see what was going on inside the bell housing. it turns out that the release bearing is bearly touching the pressure plate when i push the fork all the way back and that is why my slave keeps popping out as Datzenmike said.

 

Weird thing is, the clutch kit is new and so is the clutch collar, tomorrow ill be dopping the tansmission and will inspect the cluth pressure plate.

 

can someone please put a picture of a 79 620 clutch collar?

 

thanks, Erick

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Well the clutch collar MUST match the pressure plate. This is because the pressure plates are not only different in width 200mm, 225mm, and 240mm... but the diaphragm fingers (that the release bearing push against) are at different distances from the flywheel surface. To keep clutch arm working through the same position and geometry (and so the slave piston doesn't fall out) different length collars are used.

 

I don't have a '79 release collar picture but all L20B collars should be the same for the truck as they all use a 225mm pressure plate. Generally the larger the pressure plate the shorter the collar length. I've heard of incorrect collars being installed before and if too long the clutch doesn't fully engage and acts like you have the peddle down slightly... might even slip. If too short the clutch doesn't fully disengage and acts like it isn't even working and cant get into gear.... grinds into reverse.

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whatever collar was with your L20 is the one you use.

most clutch kits do not come with collars so you use the old one.

 

Now if your truck was a L16/18 then it used a 510/521 collar. Now you have a L20. Is it a 225mm flywheel like for a 620 I will assume YES and you need the 620 say a 78-79 collar.

 

I believe partstrain sell new collars.

Napa used to sell a collar and bearing together at one time for 510s.

 

 

PS to me those look like 200mm bearings at least in the photos. YOu have a 200mm flywheels????

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