Rochester

iTrader: (9)

Now that it's starting to get cold again, I'm experiencing an issue with my clutch pedal. It's very soft at the top, until the car warms up, and then all is right with the world. For background:
.

• 40k miles on the car and original clutch.
• OEM Clutch Slave Cylinder replaced at 18k miles.
• RJM clutch pedal assembly for the last 20k miles.
• Clutch fluid drained, filled and bled by my mechanic about 500 miles ago.

I suppose it could be air in the line since the fluid swap, but why now and why because it's cold? It could also be the CSC failing again, although the first time it failed without warning, dead to the floor. It could also be the Clutch Master Cylinder.

Anyone have any insights into this problem? Kind of scary reliving that feeling from years ago where you can't trust your clutch.

[edit]

I'm going to replace the Clutch Master Cylinder.

JSolo

iTrader: (14)

Did the level in the reservoir change at all?

Are you in a position to bleed it yourself (or with a helper)?

Might be the master tooż? Not sealing well enough until fluid is somewhat warm (seals becoming more pliable when warm).

Rochester

iTrader: (9)

Nope, level is topped off. I checked.

No, I'm not really up for bleeding it myself. I'll have to hit up my mechanic for that.

Master... ugh. Do you have to lower the transmission for access to the CMC like you do the CSC? I can't say as I'm mechanically familiar with these parts.

JSolo

iTrader: (14)

Master should be removable from the top. Might have to move some brake lines out of the way. I recall reading removing a stud from the mc mount makes it easier. The 370z mc lacks the damper the g37 models have, making it easier to install. IIRC, rjm has a heavy duty master available.

Still, I think starting point is to bleed it again. Wonder how your mechanic bled it. I use gravity bleed for 4-5 refills of the reservoir then traditional (with helper) bleeding for another 1 - 1.5 refills. Got that fall colors cruise coming up this weekend and it's supposed to be chilly (40's). Hopefully no issues.. ~35K on the car now.

Rochester

iTrader: (9)

I agree. I should start with my mechanic and a re-bleed. Does it make any kind of sense thinking air in the line, with a problem like I'm describing being after the car cools down?

It's sucks when you lose faith in the simple mechanics of a thing like a clutch pedal. But having the pedal drop to the floor and stay there like it did when the CSC failed 4 years ago... that kind of thing really sticks with you.

JSolo

iTrader: (14)

I hear you. I experienced this on one of my motorcycles. Grab point kept changing. Couldn't figure out if it was the slave or the master or both. Eventually got rid of the bike before the issue was fixed. Next one had a cable clutch. I had almost 40K on the bike in less than 3 years. Had I kept it longer I would of just replaced the cable for good measure and called it a day.

No extended warranty left on the car?

Rochester

iTrader: (9)

6 year/70K drivetrain warranty. So... no. I'm on my own now with this car.

6MT>7AT

I've had this issue in the past but noticed that it only seems to occur when I leave the car in gear overnight. I don't understand the correlation or if it's just a coincidence but figured I'd share to see if you notice a similar occurrence . In regards to having air in the lines I had this occur after changing my clutch fluid and this caused my clutch to go completely dead and would basically have to be resuscitated by pumping it about 20-30 times every 10 minutes. I was able to get it to my mechanic by constantly pumping the clutch while at stop lights.

Rochester

iTrader: (9)

Not a mechanic, but I can't see why leaving it in gear would matter. I typical leave it in gear while in the garage, but it's easy enough to stop doing that and just leave the P-Brake on.

Yikes! Scaring me, man.

I'm wondering, if it's air in the clutch line in direct correlation to having the clutch fluid swapped 500 miles ago, then why did it take so long for the problem to bubble up? (no pun)

6MT>7AT

I'm wondering, if it's air in the clutch line in direct correlation to having the clutch fluid swapped 500 miles ago, then why did it take so long for the problem to bubble up? (no pun)[/QUOTE]

Yeah for me the problem occurred directly after changing the fluid so I doubt you're having the same issue. I spent a full day attempting to burp the system with no success. I won't be attempting that myself again.

Rochester

iTrader: (9)

Third morning in a row where the clutch pedal was soft from top-to-middle before engagement, then got better (normal) after the car warmed up... just a few miles. So I drove to my mechanic's shop to talk to him about it. While there, we bled the clutch line thoroughly. I'm in the car on the lift, he's underneath, and one of his guys is on a ladder keeping the reservoir topped off. Then he got into the footwell and adjusted the master cylinder... not that there was much adjustment available, maybe one thread rotation.

Drove home. For a bit, all was normal, and then it went bad while driving, reverting to that early-morning behavior all the time now. It's pretty damn scary, feeling almost no pressure at the top of clutch, and a small window of engagement, like the pedal is about to hit the floor and never come back up.

God damn it.

So where does that leave me? Replacing the Clutch Master Cylinder?

Rochester

iTrader: (9)

I'm researching CSC elimination kits. There's this thread, which died off about a year ago.

https://www.myg37.com/forums/engine-...ator-kits.html

slartibartfast

iTrader: (7)

JSolo

iTrader: (14)

I agree with starting simple, but don't agree with the above conclusion.

We know that when the CSC fails, it leaks. This means reservoir level goes down and must be replenished. What other type of CSC failure is there if the seal is not broken and leaking?

So, assuming there is no air in the system then the issue must be at the master. Given the symptoms, it sort of makes sense. There is movement within the master every time the pedal is pushed. I don't know what these seals are made of, but probably some form of rubber. When cold, rubber isn't as pliable compared to when warm. So it's possible, because of wear, it isn't sealing as well until the assembly/fluid warms up slightly, and seal is able to better conform to surface.

Considering replacing a master is magnitudes cheaper than the slave, that's where I would start.

Another thing you could do is disconnect the clevis from the master pushrod. Let the car sit over night. In the am try to modulate the pushrod manually. If it's leaking internally (failed master) then the required effort should be minimal.

http://constructionforklifts.tpub.co...14-P0078im.jpg

From what I recall it's all hard lines except for a small flexible section connecting the reservoir to master.

Another thought, you have the rjm pedal right. So for typical operation, the master is not fully stroked. From what I recall in the instructions, it's advised to adjust the pedal for maximum stroke when bleeding. Was this done?

Rochester

iTrader: (9)

Well, that's certainly true. Awkward to access, but nothing as major as a transmission drop.

OEM Master Cylinder, Jsolo? I'm not finding any big aftermarket for the CMC.


I don't know what this means. The RJM is dialed all the way counter-clockwise, for widest engagement.

I know this because just the other day I was thinking engagement was pretty narrow, and when I went to check the lock-out screw was loose, and apparently it wiggled clockwise over time, instead of the other way.