Even if it is an available part from somewhere, I still would not re-build the slave cylinder. I know one of mine, and likely many others failed not because of the seal, but because of the little ball thrust bearing in the end of the piston. That is the "throwout" bearing for the clutch, and is spinning all the time the engine is running. A lot of motion on a very small bearing, lubricated only with the little bit of grease in it from the factory. Rebuilding a slave with a new piston seal will only make bearing failure very likely to be next. When that bearing tightens or seizes, the piston spins in the cylinder, wiping it out immediately.Fred said:just a quick question? does anyone know the seal number and manufacturer for the clutch cyl.seal? I am not looking for the oem number since I don't trust their quality.
David.....OMG.... that bearing at the end of the piston spins at "all times"? I thought it spun only when the clutch was depressed under pressure.dshealey said:That is the "throwout" bearing for the clutch, and is spinning all the time the engine is running. A lot of motion on a very small bearing, lubricated only with the little bit of grease in it from the factory.
hoodoodrum said:David.....OMG.... that bearing at the end of the piston spins at "all times"? I thought it spun only when the clutch was depressed under pressure.
Yes, it spins all the time. The spring in the slave cylinder keeps pressure on the piston, forcing it and the clutch actuation rod forward against the diaphragm clutch spring. The pressure is not near as much as when you pull the clutch handle in to push the clutch spring open, as the pressure is then pretty high, but the actuation rod is always under spring tension from the cylinder spring. When you install the slave cylinder the pressure you have to push it in with, and use the screws to pull it in and seated, is always there, so the bearing is always spinning when the engine is running. Can't avoid it.hoodoodrum said:David.....OMG.... that bearing at the end of the piston spins at "all times"? I thought it spun only when the clutch was depressed under pressure.
No typing slip, the actuating rod and piston bearing spin all the time the engine is running. Even when the clutch is pulled in, and or transmission in neutral, the rod is still pushed against the diapraghm spring, which is spinning with the engine. The only thing in the whole clutch assembly that ever stops spinning is the clutch disk itself when the clutch is disengaged. The rest of the assembly: drive plate, diapraghm spring, pressure plate, and clutch cover plate are all attached to the engine output shaft, so do not stop spinning.Tourdog said:David knows that, HoodooDrum it was a slip of the typing fingers.
Right. You have replaced slave cylinders, and know how much spring pressure is on it when you install it. With the clutch released, the slave cylinder spring is pushing pretty hard on the piston. That pressure never goes away. The bearing sees considerably higher pressure when the clutch diapraghm is being pushed in, but the released pressure is plenty high enough that the bearing has to spin.cccpastorjack said:...and David can speak for himself, but I would be willing to bet that the bearing spins MOST of the time, if not all. It would seem that even the lightest contact would spin the bearing...hence, it wears out, ruining the cylinder. Hum Dave????
The forward end of the shaft goes through the clutch diaphragm spring and into the engine output shaft. The part that rests in the center of the diapraghm is as large as what rests against the piston bearing, but chamfered, so actually more surface area. The rod never spins against the diapragm spring, even if lubricated. I put a little lube on mine, but next time it was removed there was the normal expected brown "fretting" on the forward end, no rotational movement evident.Tourdog said:The clutch rod spins whether engaged or disengaged. But, thinking it thru with a mechanically (but adjustable) actuated clutch vs the hydraulically actuated that is "not adjustable" but fixed by virtue of engineered position, throw, and rod length yields little difference. But, since the clutch rod dead centers on the diaphragm spring and therefore, no radius (for torque) it then has the possibility of an infinitely tiny point which produces zero rotation. A dab of required grease at the pointed end (to take care of the non-infinite) and a larger dab at the slave thrust end will reduce compression friction especially when the clutch lever is relaxed (ie engaged) and IMO it will rotate little. It is those that do rotate that ruin the slave bearing (spins the piston) and scour the slave walls and R & R is required. I venture that most who do the "slave", R & R, never pull the slave apart so they don't know if it spun or not. If much rotation was expected by BMW engineering that slave bearing would be more robust than it is.
Is there any temporary addition of fluid that might last long enough to get me to the dealer and, if so, where does that fluid go? The fluid normally goes right into the clutch assembly! Unless a line broke, that is about the only result, if the drain hole has not been drilled. Unfortunately, you probably are looking at a slave cylinder and clutch replacement. There is nothing you can do to make it better. You can add brake fluid, but that will only help you get it going for a short time, and put just that much more fluid into the clutch.ltcommuter said:--------------------
The fluid leaking from the swing arm boots is completely unrelated to any clutch issues, as there is no commonality at all. No way for brake fluid from the clutch actuation system to get there, period. That is transmission fluid if coming from the small boot on the front of the swing arm at the output shaft of the tranny, final drive oil if coming from the boot in front of the final drive. Neither of these is as drastic or as expensive as the slave cylinder failure though.Possibly related to this dilemma is the fact that fluid has been leaking from the boot next to the final drive. It doesn't look like oil and could be brake fluid. I made an appointment to get it fixed next Tuesday.