change out the clutch master cylinder. mine didnt give me any issues until after i put on a AP braided clutch line. i changed out both the master and slave....back to normal.

 

I winded up getting the clutch replaced from the Nissan dealership. They told me the clutch was gone...so be it since I know it had been getting soft for awhile and I figured, got the car used, what the hell...let's get it replaced but they couldn't fix the spongy soft clutch issue. The funny thing is that the engagement point was really short and took awhile to get used to driving it (no high engagement point anymore...definitely more natural and fun to drive) BUT....it winded up doing the whole...getting stuck half way.

After the tech admitted that they weren't sure (and I figured I want to keep this ride for another 3years); I took it to the Infiniti dealership and they couldn't figure it out. They pretty reassembled the engagement point so it's much higher now and the clutch is definitely springy again but they said the master/slave cylinders were fine (I wonder to be honest) but figured...what the hell, I have a year warranty on the clutch so if it acts up more; I'll take into Nissan and see what they say....all I can say is even after dropping the amount of $$ on this car; I'm seriously wondering if I should look to get something else altogether. This car is really beginning to be more trouble than fun; maybe it's time for a early year Porsche or something (something that will justify the $$ that is put into the car)

 

I want to throw in my 2 cents here. I know it has been said many times but change the fluid in the clutch line. Open up the bleeder at the slave cylinder and bleed the hell out of it. Do the changeover technique at the master cylinder over and over again. Leave it open for a while and let all the fluid drain out. Detach the line at the slave and let it all bleed out. Do anything possible to get all of the fluid that's in there out, it's not easy and takes a while. It is very hard to get all of the old fluid but it needs to come out. The fluid in my lines was so bad, it smelled horrible and was so dirty. It is worth a try and it worked for me.

 

I would think bleeding by constantly refilling the reservoir would be better, because bleeding air out of the lines is a PITA.

 

There is no "return line" per say in the clutch system, only the one line going from the master to the slave. You can bleed and refill that resevior all you want but all the crap is at the bottom of the system. Whatever garbage fluid and junk that's down by the slave and in the lower line will never come out without draining or proper bleeding. Yes bleeding the air out is a PITA but nothing worth having is ever easy right?

 

No no, I meant draining from the slave, but keeping the tank full as it drains out. I did it with a brake bleeder kit: hooked hose to slave bleed valve, and pumped clutch until nice clean fluid started coming out (keeping the tank full during the process).

This siphon from the top only stuff is for the birds, see my posts above from June. I guess people feel good because the fluid in their tank is clean, but their lines are full of crap. Bleeding the lines is the only way to get good fluid to the master/slave cylinders (where it's needed most).

 

Oh yea right on. I just mis-understood.

 

Had the clutch sticking problem in my 2005 sedan when it got hot and changing the fluid in the reservoir corrected the issue for me. About a year later the sympoms came back and had to do it again. I never bled the system. I agree bleeding the system is better, but changing just the resivoir fluid was a lot easier at the time.

I was hoping I was done with that when I upgraded to a 2008 sedan, but at ~24,000 miles the cluch pedal was getting intermittently spongy and looking dirty so I did the same quick and dirty reservoir replacement procedure. I never actually had the pedal stick on the 2008 yet, but it definitely wasn't right, particularly when it was cold or hadn't been driven for a couple of days. I plan bleed the system next time I change my engine oil.

 

dont see very many comments lately on the Valve Body shuddering down shift problem, perhaps because it is old news but have a question for anyone who has opinion. My 2006 Coupe AT has this problem. It is not terrible just happens when the RPM falls into the 1500 range loping along. Easy enough to fix with higher RPM (please dont throw me in that briar patch brr Rabbit) but if you dont correct the problem does it continue to get worse and eventually just fail stranding you or is it a characteristic problem of the car? Expensive repair but not too troubling at this stage if it doesn't get alot worse. I service trans but didnt seem to do too much.

 

I had the same BS clutch problems. Would get harder to shift the hotter the car got, and the pedal would always stick.

I took it in, complained, and had them look at the cylinders, and then they called me later that day and said "Your slave cyl is shot, so we're replacing this under warranty"

So far, I have NOT noticed anymore sticking or pedal feel problems, the shifter works much better, and it's eaiser to take off smoothly

Now, how a CPO car gets "certified" with a shot clutch and slave cylinders.... that's another story.

Still not an Infiniti fan, but this made my car much more enjoyable for the time being.

 

I am from Australia and I have exactly the same problem bothering me since I got my Z used a year ago. I drove a lot in the city in a stop and go traffic, it always happened when hot day+city drive. I came across couple websites reckoned changing the clutch fluid to dot 4 would help. I gave it a try and it actually helps, the sinking clutch never come back again. But thing is whenever I depress the clutch pedal, I can feel that it is not a smooth action. My question is, would a bad slave/master cylinder contribute to this? My mechanic suggested it might be the seal gone bad on either or both slave and master.

 

My pedal was sticking all the time, not just when hot. Changed the fluid, didn't help. Bled the crap out of it, didn't help. Did the slave yesterday, didn't help....... grrrrrrrr
One suggestion when when changing slave or MC, have a helper with you! After doing the slave, the pedal just dropped to the floor. No engagement AT ALL. Finally had the girl friend come over and pump the pedal for me while I bled. It took a LOT of bleeding just to get it back where I started.

I guess I'll try the master cylinder next.........

 

A lazy return or pedal not returning all the way and hanging about half way will be caused by a worn clutch master cylinder 99.5% of the time. What happens is the clutch forces the slave back which in turn pushes fluid back to the master cylinder, if the seals are weak in the master the fluid by- passes the seals and goes into the reservoir instead of pushing the pedal back to the top position

 

Background: 2005 G35 Coupe 6MT. Approx. 100k miles.

I am also having problems with the clutch pedal sticking 2/3rds of the way up when the temperature gets hot and I'm in stop and go traffic for more than 20-30 minutes.

I used the Ranger method weekly for a month and went though 1.5 bottles of Prestone DOT 4 Synthetic fluid. Unfortunately, this did not resolve the issue.

This morning and I bled the system from the Slave Cylinder and was surprised by the condition of the fluid. Attached is a picture comparing the fluid in the reservoir after a months worth of Ranger fluid replacement and what came out this morning from the Slave Cylinder.

I do not drive aggressively and shift at or below 3k RPM. This may be a reason why the fluid is not cycling through.

That said, I would recommend that people take the additional step and bleed the fluid from the Slave Cylinder to thoroughly purge the old fluid out of the lines. .

 

So lots of you are saying when it gets hot the clutch wont come all the way back up. I'm experiencing the opposite. When I start my car first thing in the morning the clutch is close to the floor and when I let off of it it doesnt come all the way back. Once i've been driving for some time and the engine is warmed up it will start to fully come up. But then the engagement point is higher as well.

Thoughts on why this is happening? I've done the clutch adjustment mod and also changed the clutch fluid with fresh synthetic DOT4 fluid. Next step was to bleed the clutch line and make sure there is no air in the line. Any other suggestions?