I've got a RJM story, four years later.

My clutch slave cylinder failed at 18k miles, replaced under factory warranty.
At 20k miles, I had this RMJ pedal installed.
At 40k miles, this happened...

I had my mechanic swap clutch fluid (which is just OEM brake fluid), along with a whole bunch of other fluid swaps. Around that time, I was tweaking the dial-in on my pedal, because the retaining bolt had loosened and the dial swung all the way clockwise. I prefer it all the way counter-clockwise.

Then one morning three weeks ago (and 200 miles from home), I got in the car and the clutch pedal was super weak at the top. It was kind of scary, but I drove it anyway. After the car warmed up (and subsequently the clutch fluid I suppose), the problem went away. This occurred each morning for two days. I had my Mechanic bleed the line again, but it didn't matter, and the pedal stayed weak at the top all the time.

The car sat for the last three weeks, because I couldn't get my mechanic's attention. He's got skills, but he's also kind of bipolar, and kind of a d1ck. So I looked around for another shop. Found one closer to home, with a great reputation. Thought I'd give them a shot. The tech who worked on my car was a Nissan tech, and is familiar with the G/Z platform.

I gave him the car, and a brand new Clutch Master Cylinder for install. However, instead of installing the new MC, he determined the RJM pedal was configured too high in comparison to where the OEM pedal should be. I said, "Yep, that's how I like it." But he said that was part of the problem, and it was compromising the geometry of the pressure against the MC pin. He moved the pedal back down, and all was right with the world again.

I was shocked.

He also found a TSB that claims Nissan now recommends GTR brake fluid in the clutch line for the G/Z. I didn't know that, and apparently neither did my old mechanic. I'm going back next week for another clutch fluid swap, this time with GTR brake fluid.

So perhaps a combination of changing the dial-in on the RJM, having the pedal too high, and recently swapping in old open-air OEM fluid instead of new, un-opened GTR brake fluid... I don't know. Whatever the combination of factors, I was having problems.

And now I'm not. Yay!

 

Nice! glad the car is good to go again... also good that you picked up a second mechanic as a go to in the process in case you have issues in the future with the car or the other mechanic

 

That is interesting about the RJM clutch pedal assembly. Unless the GT-R fluid is free, I would not worry about it in your car for the street. They probably have this listed for all G37 and 370Z's with a 6spd. manual as it can be an issue on track with the high temps. I ran into this at Road America once as I was holding the clutch in just a touch too long when I heel and toe downshifted and the pedal went to the floor. I immediately changed my technique and the pedal was fine. I got Z1's insulated clutch line and upgraded to Motul RBF600 fluid in the clutch line (same stuff I use in my brakes) as a precaution and never had the issue again.

I am glad to see that Nissan is trying to upgrade their cars for track use. I first saw this as an oil cooler on the 370Z and then it gained better brake pads. I think it was last year they upgraded the clutch. Now if they would just upgrade the rest of the car to a new model...

 

Always nice when you take a chance on a new mechanic and they meet/exceed expectations.

 

$38 shipped for a quart on Amazon.


Oh yeah, for sure. Huge relief.

 

Skip it. That is total overkill for the street. If you have your heart set on high temp track fluid (why?) then get Motul RBF600 for half the price because it has a higher wet boiling point (the only reason to get high temp fluid in the 1st place).

 

Well, no, I'm ambivalent about it supporting high temps for track days, because I don't have track days and live in the Northeast.

However there is a TSB which says to use the GTR Brake Fluid for the G/Z 6MT.

http://static.nhtsa.gov/odi/tsbs/201...51925-8330.pdf

 

Interesting follow up...my 07's G35s CSC failed at 55k, installed the RJM on the '12 G37s currently at 36k no failures yet. What did you adjust the RJM settings to?

 

Counter-clockwise all the way, then half a turn or so back. (It's the v2 pedal.) But the technician was solid in his opinion that I had the pedal too high. He lowered it back down just above the brake pedal. Apparently that's all it took to fix the problem. Can't say as I understand it all, but it's what happened. Like I said, seems the geometry was slightly off somehow.

I think Nissan's Clutch MC and Slave are maybe not the best design overall. But I don't know really.

 

so how does having the pedal too high affect your issue of low pressure in the morning then builds pressure when its warmed up?

 

If I were to put on my poorly fitted, armchair engineer hat... my guess is the seals inside the MC were compromised somehow. Years of having the pedal configured that way? I don't know. The introduction of near freezing temps in the late fall, coupled with the intervention of having the system bled and refilled with whatever-was-on-hand brake fluid. Some one thing or combination of things pushed the tolerance over the hump and caused the problem. Lowering the pedal fixed it.

Seriously, the only thing that's true is that lowering the pedal fixed the problem. That doesn't mean I can explain it.

 

i guess i dont get to see if there is any feel difference with the z mc lol

 

I hadn't thought of it like that. Oh well.

 

I'm having a hard time wrapping my head around the solution. Just how high was the pedal? Maybe the pedal was not adjusted properly so the equalization port (I think that's what it's called) in the MC wasn't able to function properly. IIRC, in part the adjustment of the cruise/neutral switch determine limits of either position.

Maybe @Motorvate can chime as as he's probably had his MC apart.

With respect to the gtr fluid, wasn't that the band aid so as not to replace the CSC?

How many cold mornings have you driven the car now?

 

I'm with you on this, Jsolo. I think I'm going to write to RJM with the situation and see if he has an insights.

IDK "how high" other than to say it was noticeably higher than stock. It's adjustable, and I liked it that way, so what's the problem, right?. But when this new technician went to replace the MC, first he started eyeballing my RJM pedal configuration and said right away he knew it was too high. Adjusted it back down, and all the sloppy play disappeared.

Why did it take four years for this situation to come about? What's the relationship between cold fluid temp and what was happening? Why did moving the pedal to a more normal position make it go away?