Repeatedly low clutch
 

Hi all,

I've lurked the forum before and see that people have had this problem before but have not found a solid solution.

My 2009 repeatedly develops a low clutch bite to the point that it becomes very difficult to shift gears (sometimes impossible). I've brought it to my mechanic as this is a bit beyond my comfort level to repair at home and we have replaced every component of the clutch over 4 separate visits + once where he vacuum bled the system through the reservoir.

Sure enough, the clutch works great for a couple 100k and then gets spongy at the top and a progressively lower bite point. It's almost certain that air is getting in (no fluid leaks and reservoir stays at same level).

Anybody have an answer here? I've heard the system is difficult to bleed, my mechanic knows this too (He's been doing his homework on this issue and I trust him) but without doing it myself (which I don't think I can accommodate) I'm not sure what to do here or how to solve this.

If the clutch works fine after your mechanic vacuum bleeds the system then you're probably getting all of the air out. Did you mean to write 100k miles? That's not a bad interval to have to deal with this.
Your problem may have more to do with moisture than air. If you've never flushed out the 15 year-old fluid in the line and the slave cylinder, replacing it with fresh, dry brake fluid may do the trick. I've never had this problem, but I have replaced very old fluid from the system and then seen it separate into clean looking oil on the bottom and black water floating on top of it. The fluid in the reservoir always looked clean, but moisture got in below that.

Hey 89longbed, thanks for writing,

Not 100k miles, "couple 100km", it's definitely a short amount of distance that I'm driving before the clutch drops little by little. I changed the fluid was changed and to be honest it didn't look too bad. Plus the number of times that clutch has been bled in the last couple of months, I'm sure everything I put in there has been replaced at the mechanic anyways.

Almost certain that air is sucking into the system and the softness in the clutch is the compression of that air.

I wonder if there is a way to pressurize the sytem and do like a soapy water test on the seals?

If you are having a good clutch after bleeding and it slowly gets bad, it is very likely that you are getting air in the slave past the O-ring in the line disconnect. I had this problem and just delt with it for a year by bleeding it every 2 to 3 weeks. I was taking my transmission out to replace it and decided to replace the slave while at it. I kind of suspected the O-ring was bad, so I removed it and replaced it with a new one. The old one was damaged, and I am pretty sure that was where the air was getting in.

It could have been the slave too, but it was fairly new and should have been working well. It has been almost a year since replacing the O-ring and slave and it has never worked better than it does now. That O-ring is an easy replacement item.

I don't think pressurizing the system will help you to find where air is getting sucked in. I had no fluid leak at all, just air getting sucked in. So, pressure was not the problem. I think when the pressure plate pushes the slave back and draws fluid back from the master cylinder, it creates a kind of vacuum that can pull in air past a bad seal like the O-ring and possibly even the slave seal.

Problem was solved. It was the slave cylinder sucking air. It was only 1.5-2yrs old so, although past warranty my mechanic reached out to his supplier and they offered a replacement slave plus 75% off labour cause a slave shouldn't fail after that amount of time/mileage.