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Old 12-03-2013, 05:22 PM
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trouble bleeding throwout

hey so I just installed a sm465 in place of a th350 .I got a howe hydraulic throwout bearing .everythings in and I went to bleed it and I got no fluid only a couple of drips comin from the throwout bearing.i bench bled the master cylinder.but ive been at this for 2 days and have had no progress on getting any fluid through the bleeder screw..any suggestions would be awesome id like this swap just to be done.

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Old 12-03-2013, 06:08 PM
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I'm not familiar with the throwout bearing you're talking about but I have quite a bit of experience with Ford hydraulics which are about the worst to bleed. The key is to remove the air that gets trapped in the line between the master and the slave. Ford uses a valve at the end of this line. The valve closes when you disconnect the line from the slave. Normal procedure is to have a helper depress and hold the pedal while you depress the valve and release pressure until the pedal doesn't depress. This means that the line is full of fluid and no air. Then you connect the slave and bleed it and you're done. The trick is that air gets trapped in the line, especially since they designed a loop into it. In order to get the air out, you need to hold the valve end up so that any air in the line can get to the valve by gravity. Then you can bleed it out. I cheat and use a pressure bleeder cause I hate to wait for helpers.

I don't know if your system is anything like the Ford, but it sounds like it might be. If there is no valve at the slave end of the line, you should be able to pressure bleed or even vacuum bleed it. Of course you'll need the equipment for this. If no valve then your problem is probably just a loop in the line trapping air.

We've also had some success reverse bleeding these systems. Reverse bleeding is just a matter of injecting fluid at the bleed screw using either a pressure bleeder or a hand pump type injection gun. The idea is that by pushing fluid in at the bleeder, you force air up and out the master. This often works. When it doesn't, I use the method detailed above.

I hope this helps. One trick that I've also had decent success with over the years is just pumping the crap out of the pedal. The idea there is to work the air back up to the master and reservoir. You also cavitate the fluid this way so don't be surprised if any pedal you do get isn't there when you go back after an hour. You do make progress though and after a few cycles(if your leg doesn't fall off), you can get a pretty decent pedal this way. Enough atleast to get you back to old school bleeding with a helper at the pedal and a wrench on the bleed screw.

I've also had a couple of cases where the master just wasn't any good. It bypassed fluid and no amount of fooling with it was ever going to make it work. These were fresh out of the box quality brand remans too. Another MC and the system bled out right away.
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Old 12-03-2013, 07:43 PM
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well thanks for the advice the bearing i have is the hydraulic throwout with no slave cylinder or clutchfork it just rides on the input shaft with one line to the master ..that bein said the thing and the bleeder screw is inside the bellhousing and im doin everything through the clutch fork hole.in hindsight i should have bled everything as a unit before i installed it in the truck but hindsight's 20/20 .i think i might try the pressure bleeding again.i would try the reverse thing but i cant get to it i had to weld a 1/4" wrench to a piece of round steel to reach the bleeder screw.
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Old 12-04-2013, 06:18 AM
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What you describe is just like the Ford design. The slave cylinder is integral to the throwout bearing. Ford is at least nice enough to put the bleeder at the end of a long tube that extends to the opening in the case. This makes access to it much easier. I'm sure that the problem you're having is the same as I've seen many times with the Fords. Pressure bleeding doesn't work because it doesn't remove the trapped air from the line. I know that others have adopted the same integral slave/thowout design but Ford is the one that comes to mind because it's always a pita to bleed.

One other possible issue is that the master cylinder isn't returning to the full rest position. The MC has a small relay orifice at the very back end that opens only when the piston is fully retracted. This orifice allows fluid to pass through the cylinder between the slave and the reservoir. This prevents slave apply due to heat(fluid expansion) and it also allows air to move through the MC to the reservoir during bleeding. If the piston isn't allowed to fully retract, due to the rod being adjusted too tight, this valve doesn't open and bleeding is much harder. with this valve closed, pressure bleeding is nearly impossible. Be sure that the push rod is loose against the piston with the pedal at the top. The way I tell this is by looking for the rod end to be loose at the pedal arm.
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Old 12-04-2013, 08:54 AM
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Quote:
Originally Posted by erich545 View Post
well thanks for the advice the bearing i have is the hydraulic throwout with no slave cylinder or clutchfork it just rides on the input shaft with one line to the master ..that bein said the thing and the bleeder screw is inside the bellhousing and im doin everything through the clutch fork hole.in hindsight i should have bled everything as a unit before i installed it in the truck but hindsight's 20/20 .i think i might try the pressure bleeding again.i would try the reverse thing but i cant get to it i had to weld a 1/4" wrench to a piece of round steel to reach the bleeder screw.
I have the Howe bearing but have not got it installed yet. My plan is to run an external bleed line outside the bell.

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...One other possible issue is that the master cylinder isn't returning to the full rest position. The MC has a small relay orifice at the very back end that opens only when the piston is fully retracted. This orifice allows fluid to pass through the cylinder between the slave and the reservoir. This prevents slave apply due to heat(fluid expansion) and it also allows air to move through the MC to the reservoir during bleeding. If the piston isn't allowed to fully retract, due to the rod being adjusted too tight, this valve doesn't open and bleeding is much harder. with this valve closed, pressure bleeding is nearly impossible. Be sure that the push rod is loose against the piston with the pedal at the top. The way I tell this is by looking for the rod end to be loose at the pedal arm.
These Howe bearings don't retract, at least mine doesn't. I've tested it with air and wherever you stop it, it stays put. No internal spring. It's kinda hinky in that the lines are on the part that moves with the actual t/o bearing while the base housing stays immobile on the input shaft.

Russ
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Old 12-04-2013, 07:17 PM
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I got it yall. I cracked the line comin from the master while the pedal was down and got the last of the air out duhhh.then it was good to go.by the way they should highly recommend the external bleeder line I had no idea.well lessons learned I guess haven't test drove it yet ill let yall know
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Old 12-04-2013, 08:32 PM
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A vacuum pump with a brake fluid adapter might have made it a lot easier too.
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Old 12-05-2013, 05:41 PM
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yeh thats what I used
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