How does the slave cylinder leaking damage the clutch? - BMW Luxury Touring Community
 
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post #1 of 10 Old May 2nd, 2009, 10:02 pm Thread Starter
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How does the slave cylinder leaking damage the clutch?

I've just finished the 36k mile service and was going to start the weep hole project. I'm looking at the Clymer manual and the BMW manual and I can't figure out how a slave cylinder leak can make it through the transmission to the clutch? Can someone please explain this to me.
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post #2 of 10 Old May 2nd, 2009, 10:04 pm
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Re: How does the slave cylinder leaking damage the clutch?

The transmission input shaft is hollow and the clutch release rod resides inside it. One end in the throwout bearing at the end of the slave and the other end inside the clutch housing. I guess I should add that once the leak starts there is no where for the fluid to go except down the rod and into the clutch. The weep hole may or may not let all the fluid out but at least you will KNOW you have a leak if you check it periodically.

John
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Last edited by jzeiler; May 2nd, 2009 at 10:11 pm.
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post #3 of 10 Old May 2nd, 2009, 10:08 pm Thread Starter
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Re: How does the slave cylinder leaking damage the clutch?

Thanks John,
I thought there was a reason. Do you know how much clearance there is between the slave cylinder and the transmission wall when the cylinder is installed?
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post #4 of 10 Old May 2nd, 2009, 10:13 pm
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Re: How does the slave cylinder leaking damage the clutch?

From the face of the slave to the boss with the rear shaft seal is about 3/16 of an inch.

John
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2006 Bushtec Turbo+2 Spell
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post #5 of 10 Old May 2nd, 2009, 10:18 pm Thread Starter
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Re: How does the slave cylinder leaking damage the clutch?

I didn't make myself clear. OD of Cylinder vs. ID of Housing.
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post #6 of 10 Old May 3rd, 2009, 1:35 am
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Re: How does the slave cylinder leaking damage the clutch?

If you're referring to the front of the slave cylinder itself and the mating hole in the tranny, the fit is fairly close, perhaps a few thousanths. The problem is between the close fit and the gasket between the slave and transmission there is no place for any leaking fluid to go but along the shaft where it ends up dripping on the clutch. The void John refers to fills quickly.
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post #7 of 10 Old May 3rd, 2009, 5:56 am
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Re: How does the slave cylinder leaking damage the clutch?

Quote:
Originally Posted by mjordans2000
If you're referring to the front of the slave cylinder itself and the mating hole in the tranny, the fit is fairly close, perhaps a few thousanths. The problem is between the close fit and the gasket between the slave and transmission there is no place for any leaking fluid to go but along the shaft where it ends up dripping on the clutch. The void John refers to fills quickly.
Actually, the clearance around the nose of the cylinder is pretty decent, as there is a bit of a taper to the cylinder nose, and there is more than a few thousandths even at the rear of it. When the drain hole is drilled I always tried to get it to come out as close to the bearing as I could. That way the fluid has a very easy path out.

I still say the hole should be called a "drain" hole, not a "weep" hole. Weeping denotes a very slow leak, but when the slave seal fails (probably often caused by the throwout bearing tightening up and spinning the piston in the cylinder as at least one of mine did) the fluid is forced out under pressure at a pretty high rate, and you need it to "drain" out fast enough to keep it from rising to the center of the bearing where the actuator rod is.

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post #8 of 10 Old May 3rd, 2009, 10:33 am
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Re: How does the slave cylinder leaking damage the clutch?

David,


Maybe we should call it the anti-weep hole. If you don't have it and the leak develops you will be weeping when your clutch slips.

John
2009 K1300GT Red Rocket
2009 R1200GS (Gone)
2005 K1200LT Ocean Blue Blue Wizard 110 K and counting...
2006 Bushtec Turbo+2 Spell
2004 330 Ci Convertable
K4AN

Have ridden a Motorcycle in all 48
But lack DE, MA, RI and CT with the 2005 LT

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post #9 of 10 Old May 3rd, 2009, 1:40 pm
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Re: How does the slave cylinder leaking damage the clutch?

Quote:
Originally Posted by jzeiler
David,


Maybe we should call it the anti-weep hole. If you don't have it and the leak develops you will be weeping when your clutch slips.
Makes sense.

I don't want to achieve immortality through my work...I want to achieve it through not dying.

David Shealey
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EX: '01 Black LT, BAT BYKE (Totaled at 110,000 miles)
IBA SS, BB, BBG, 10/10ths.
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post #10 of 10 Old May 3rd, 2009, 8:43 pm
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Re: How does the slave cylinder leaking damage the clutch?

Yeah, it's been a while. David's right. Not sure why the clearance is relevant, with the gasket the fluid can't go anywhere without the weep hole.
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