Weird Clutch Pedal Behavior - Please Help/Advise
 

Hey guys..

I'll try to make my story short, precise, and concise..

It was Sunday afternoon/evening, I was heading back home, no cars on the highway (OK, 1 or 2 cars..)

There was my Z boringly cruising at 55-60mph in 6th gear when I noticed she wanted to go a bit faster.. I downshifted to 3rd gear to get my revs up, synchro'ed, and ready to go, sprinted up to around 120mph (shifting upwards of course), and then let go to let the Z speed down..

I repeated this a couple of times (downshifting to 3rd gear at around 55-60mph) and then sprinted up again but only to around 100mph...

I ended up again in 6th gear.. Here's where it gets weird..

While on 6th gear, I notice the clutch pedal is extremely soft and easy to press and that it had lost the majority of the engagement.. However, I still had probably 2 inches of engagement that allowed me to upshift/downshift..

I continued driving as I didn't have anywhere to stop and went all the way to the toll booth on the highway (not a very long distance but a couple of miles though..) As I approached the toll booth and downshifted to 3rd, 2nd gear at lower speeds, the clutch pedal feel came back to normal...

I paid, started slowly driving away from the toll booth in first gear, then 2nd... All normal... I then started speeding up (carefully) all the way to around 60-70mph in 6th gear and the clutch pedal started acting weird again after a couple of minutes...

As I approached my exit I started going at slower speeds and clutch pedal feel came back to normal and during normal driving for the rest of the night it continued to work normal as if nothing happened...

This morning, also, all normal as if nothing happened...

My very own graphical explanation of this follows: (red color represents where the clutch pedal gets "harder" for engagement)

NORMAL
Pedal---------------Wall
|--------------------|

WTF
Pedal---------------Wall
|--------------------|

What could have caused this? Fluid boiling because of the aggressive driving? CSC?

Should I worry and get this checked by the dealer ASAP? I'm around 1,000 miles away from the next mileage dealer service. Could it wait til then?

I appreciate your input!

I had the same experience regarding the clutch feel a few weeks ago...even so bad as to having to pull the clutch up with my toes. I've read the Master Cylinder goes bad. I already have an upgraded CSC, so the Master Cylinder is the next failing point for me.

Hey man, that sounds like a really weird problem. I'm gonna be in Panama on the 15th if you need me to bring anything back for ya.

How about a twin-turbo or a supercharger? hahahahaha...

An upgraded CSC wouldn't be too bad.. Where can I get one?

BTW, is there an aftermarket Master Cylinder or are we stuck with stock?

a possibility might be that you're clutch fluid over heated past it's boiling point and lost pressure. This can be cause by the fluid having too much moisture in it (brake & clutch fluid both uses DOT 3 or DOT 4 which is moisture absorbent) and therefore reducing the boiling point. I'd recommend a clutch fluid flush and putting DOT 4 fluid in there since it's compatible with DOT 3 and has a higher boiling point.

Upgraded CSC:

2009-2011 370z clutch kits

(They are sponsors on here - Joe@ZSpeed).

Hehe, sure I'll bring it for you but you gotta pay ;)

If you want me to bring you one, you gotta act quick so I get it by the 14th. I'll be in Panama the 15th. We should meet up!

There is no am master, only stock for now. Someone was working on one though...

I experienced this issue on the track last saturday. I had to pick up the clutch with my foot while driving the course to make it to the pits. the car was pretty hot as we did many back to back laps with little to no cool down. the fluid was a bit under the min mark, and after topping it off and letting it cool, the pedal is back to normal.

Going to try a stainless couch line with better high temp fluid before I track the car again.

Does anyone know what cases this behavior on the pedal? I am having the exact same problem on my car. 6th gear feels soft then goes back to normal!

If it's not a CSC/MC failure, then likely moisture in the fluid causing it to boil. I recall reading about a tsb for replacement of the fluid with the gtr's brake fluid (high wet and dry boiling points).

Thanks Jsolo. I will try changing the clutch fluid first to see if it fixes the problem.

Just to throw in on this old thread but i had the same issues with my aftermarket SPEC clutch and flywheel combo in the car. Replaced the Master cylinder and it solved the problem.

I actually experienced this issue yesterday. Currently in the shop. about 1 inch on engagement and wont lift the pedal back up. Changing out the CMS and doing a flush. After reading, maybe I should request DOT4 as well?

Stock Everything transmission wise... 44k Mi.

Hmmm odd... I just had this problem today. I felt like the clutch was going soft on me at certain times. It would go stiff/normal again and then go soft. I changed my line to the z1 SS and flushed with motul rbf600 the other day, and before I did this it was fine. Maybe I didn't flush it enough? I dunno...

Flush with fresh fluid first, After that doesn't help, change the master cylinder..

Nissan OEM Clutch Master Cylinder 370Z G37