Could clutch slave leak cylinder cause increased clutch wear

[brokenblinker]

I dropped my car off at the dealer last week after I had issues with disappearing brake fluid and a sticky clutch. I found (with Trent Musser's help up on a lift), where the fluid was leaking out of the connection that runs to the trans. Dealer identified it was the slave cylinder and is going to be replacing it under warranty. They told me it will involve dropping the trans.

My car has 22,700 miles on it (I bought around 16-17K). I've done 3 track days and am generally quite easy on the clutch. I have two questions:

1. I thought one time I may have felt a clutch slip around 4K RPM on track. I am not confident whether it was clutch slip, a hesitation, or some traction control system (I run in track mode, I don't turn everything off yet). Dealer quotes <$500 labor to replace the clutch and flywheel in the same job. Does this seem worthwhile? (would be almost $2k in parts for total cost of ~$2400 out of pocket if I did it)
2. I don't understand enough of how the slave cylinder works. Is it possible it could have caused increased clutch wear? Should I be pushing for this to be replaced under warranty as well? Or would it be relatively decoupled from actual clutch wear? My service advisor said they will look for fluid ingress that could impact the clutch, but that it likely would be considered a wear item and not replaceable under warranty.

Thanks for any advice! My mental model of the physical assembly is not good enough to understand whether clutch wear could be accelerated critically from a failing slave cylinder.

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[Lurker_350]

Maybe if you lose enough fluid where the clutch doesn't fully disengage when you press the clutch pedal. The situation I'm thinking about is sitting at a stop light with the car in gear, clutch depressed, but the clutch disk is dragging on the pressure plate(s) (I haven't had a twin disc clutch apart).

Or if the pressure bleeds down while holding the clutch in and it slowly starts to engage. Probably would have had to troubleshoot either of these before taking everything apart.

Seems like either possibility would present problems with shifting and odd idle speeds though. Did you notice anything that felt like the clutch dragging? For example, idle speed dropping/raising when at stop lights in gear, shifting not feeling smooth when synchros engage, etc.

If I had the trans dropped, I would probably replace the flywheel and clutch. Not so much for clutch wear, but the flywheels seem to have had issues on the FP track cars. $500 seems steep for labor. It wouldn't take me 5 hours (assuming $100/hr shop rate) to remove and replace the flywheel, clutch, and pressure plate if the transmission were already off.

 

[jmn444]

I don't think it would add to wear. When your foot is off the pedal the slave does nothing. So unless you were driving it weird to compensate for the leak somehow excessively slipping the clutch, I don't think there's any way it could hurt.

The fluid may be another issue, but sounds like that leak was external to the bell, and i'm not sure it'd get on the disk internally anyway.

 

[Skye]

I've noticed several photos on-line that show a hydraulic throwout/release bearing. Does your transmission use one? Sorry, haven't worked on a Mustang manual before. Is the throwout/release bearing suspected of leaking? That could explain many of the conditions witnessed, along with why the transmission needs to be pulled to replace it.

" I don't understand enough of how the slave cylinder works. " Older units, much older, were straight manual assemblies. Put your foot down on the clutch pedal and mechanical linkage would engage/disengage the clutch. Now, they are all hydraulic, making it easier to do the same work, with less parts, more precision and often less chance of failure. Put your foot down on the clutch pedal, and a hydraulic cylinder, nearest the clutch assembly, possibly inside the bellhousing, moves back-and-forth, to engage and dis-engage the clutch, disconnecting and reconnecting the engine from the rest of the drivetrain while shifting.

One pitfall you are witnessing is, instead of mechanical linkage breaking and the assembly stop working all-together, seals can go bad, causing the assembly to 1) leak over everything else and 2) cause partial or sometimes complete loss of engagement, due to partial or complete loss of hydraulic pressure.

If there is a hydraulic release bearing inside the belhousing, and that is leaking, along with loss of complete, positive clutch engagement, the lost fluid might have gotten everything else wet. They are probably not going to know the full extent of what's happened until the trans is pulled. The good news is, it reads like the transmission itself is OK, that its just the cylinder and maybe the clutch assembly. The clutch assembly might need to be replaced if it has been soaked with fluid.

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