engine and drivetrain Clutch Problem

[duckdudess]

My clutch engages slightly at a stop sign/light with the pedal fully depressed. It happens frequently but not consistently. I replaced the clutch master cylinder with no effect. No fluid appears to be leaking from the slave either. A weird thing I noticed yesterday is that when it begins to engage, while stopped (clutch pedal in, right foot on brake), when I rev the engine slightly, it disengages. Any ideas?

Details:

New clutch, pressure plate, throw out bearing, composite slave cylinder 3000 miles ago done at time of engine and 5 spd upgrade. All brake/clutch hydraulic lines rehabbed or replaced as needed. Fluids flushed and replaced with Castrol LMA, all lines bled.

[c.d.iesel]

bleed it again using a pressure bleeder if all your

parts are 'good'

whatsa composite slave cylinder?

[duckdudess]

I did try a pressure bleeder. I started with the brakes, which seemed to work fine, but when I opened the bleeder on the slave, not much fluid came out. I reverted to the two person operation (3 clutch pumps, hold pedal to floor, bleed, close, repeat). Perhaps I did not have enough pressure in the Motive Bleeder? Never having used one before I pumped it up to 15 PSI. Should it be higher ?

[Hans]

15 psi is enough. Did you replace rubber hose to slave cyl?

[c.d.iesel]

normally what you describe is caused by failed slave

or master cylinder seals - but you note a mix mash

of - old - used - rebuilt - new - parts so who knows which

of those are the cause - everything is questionable ???

if it's not bleeding/air in system then pick a part to replace

[duckdudess]

Thanks CD. The net is that other than the brake hard lines everything is new (3000 miles on the slave, <100 on the clutch master). I started by replacing the master which had no effect, adjusted the "pedal rod" until the clutch pedal was in line with the brake pedal, still no change and I can/will change the slave since I am running out of things to try.

[stone02]

Hi,

as i read it you replaced all the parts

for the clutch and its operation except

for one part that most people overlook.

the pilot bearing needs to be replaced

at the same time. this little bearing

holds the weight of the input shaft and

keeps the internal gears running true.

when the bearing begins to fail it

usually binds on itself. the result of this

binding is that the input shaft rotates with

the crankshaft. if this problem remains

after you bleed the clutch master and

slave cylinder then you most likely

will have to replace the pilot bearing.

let us know the outcome.

good luck

stone

[duckdudess]

Well, I will have to confirm it, but the engine was completely rebuilt 3000 miles ago, and I assume that the pilot bearing was replaced along with everything else. If that turns out to be the case, any other ideas ? Sadly though, since that is a major PITA to remove, it may be may only choice....

[Hans]

The 5 speed requires a specific pilot bearing dimension which is different than the stock 4 speed. So it may have been new, but was it the right one? If not, even full extension of slave will not totally release the pressure plate. Coming back to the lack of fluid at bleeder, is there a rubber hose in that line, and if so, is it new-ish?

[Guest_anonymous]

The 5 speed requires a specific pilot bearing dimension which is different than the stock 4 speed. So it may have been new, but was it the right one? If not, even full extension of slave will not totally release the pressure plate. Coming back to the lack of fluid at bleeder, is there a rubber hose in that line, and if so, is it new-ish?

elaborate: Do you mean the Throw out bearing here. Where if the user has a 228mm flywheel/pressure plate/clutch and the 320i TB instead of the 323i TB the TB will not fully depress the pressure plate.

I read Stone to imply a partial or complete seizure of the pilot bearing within the crank cavity causing the crank to force the movement of the trans input shaft inadvertently.

[Hans]

Apologies for confusion. Trying to multi-task here. I meant throw out bearing.

Here's what I got from Mike Miller some years ago.

"The 323i release bearing is 30mm and the regular 2002/320i release bearing is 25mm. (The former is old style steel and the input shaft flange it rides on has to be lubricated; the latter is the new style dumbed-down plastic kind that we're not supposed to lubricate, but I do anyway.) You have to use the 30mm 323i release bearing if you want to install a Getrag 245 gearbox in a 2002 with a 228mm clutch. It is part number 21 51 1 204 525.

Best regards,

Mike Miller

BMW CCA Roundel Magazine Technical Editor

techtalk@roundel.org

auspuf2002@aol.com

I had the same problem with the C/R 5 speed in my car - I don't recall specifies of sizes, but I installed transmission after changing to 228 clutch with the wrong bearing and spent days screwing around with hydraulics and push rods until the bearing issue dawned on me. Took out transmission, changed bearing, and all was well.

But I'm still curious about the lack of fluid.

[duckdudess]

The engine is a stroker, with an S14 crank. The builderknew it was being connected to a 5 speed so I am assuming that it is fine, especially since the car ran without fault for the last 3K miles.

On the line between the master and slave, it is a combination of rubber and hard line. Both 3K miles old.

[duckdudess]

Sorry, for replying out of sequence, but I appreciate the help. This car has a stroker M10 motor, a 325 flywheel with a "big" clutch and pressure plate and the new style (plastic?) throw out bearing. Again, all of this worked from day one (3K miles ago) when the new engine/clutch/pressure plate/hydraulic system was mated to the used 320i 5 spd, until a couple of weeks ago when I started having this weird problem.

[Hans]

Has this been a problem for 3000 miles or something new? If rubber hose is new, we can rule out swollen hose problem. I have read that bleeding those later style slave cylinders is difficult because of upside-down nipple location. Bav auto sells a special tool to bleed it while unbolted from bell housing. I have one somewhere but haven't used yet (awaiting O/D 5 speed conversion).

[duckdudess]

New problem. And yes, the bleeder is upside down. I'll check for the Bavauto gizmo. Thanks.