Clutch issues

[LEMHEAD16]

First, I've searched everything I can on this and am still stumped. My car will not go into gear when it is running, goes into gear fine with engine not running (duh)

I've replaced the clutch slave and master cylinder and bled the snot out of them. I have a one piece braided line from the master to slave so no fender bleed point. I've also adjusted the clutch pedal as detailed in the conceptZ write up.

With the car off the clutch pedal feels fine pressure starts about a half inch from the top. As soon as I tun the car on the clutch pedal gets much softer, almost too soft. I've checked to make sure the clutch booster is holding vacuum, it holds 15hg for 30 minutes so I don't suspect there is anything wrong with that.

The clutch Slave cylinder moves the clutch fork about 1/2" when fully depressed. I made a slightly longer push rod for the slave to take up the free play that was there but it still won't go into gear.

I'm guess I'm probably looking at a problem inside the bell housing at this point just wondering if anyone had any other ideas before I tear the transmission out again. It was running fine and then over the course of a 500 mile road trip it got to the point the clutch pedal only had about an inch of pressure off the floor. Got home and the next day went to drive it and it wouldn't go into gear.

[PapaSmurf2k3]

If you pull the slave off, can you rotate your fork all willy-nilly?
You may have broken the pivot bolt inside the trans...

[LEMHEAD16]

I pulled the slave cylinder off and there is some movement on the clutch fork but I can see the pivot ball and it looks intact.

Just for fun I put a tie down and the clutch fork and pulled it back, when I do that I can put the car in gear with it running. There's no apparent leaks in the clutch line and after its bled I get 1/2 inch movement at the slave cylinder.

I'm stumped. I might try another slave cylinder and see.

[PapaSmurf2k3]

Yeah, that or a master.

Z32s have a clutch booster huh? Maybe delete that sum b**** too.

[Ace2cool]

Yeah, they do, and most people do delete them. At least the TT's do. I don't think the N/A did.

[LEMHEAD16]

pulled the transmission, nothing appears to be wrong with clutch disc or pressure plate. frustrating.

Oh well, guess that narrows it down to clutch booster. I ordered a new clutch and 350z clutch fork while its out.

[LEMHEAD16]

Put the trans back in with new parts. No surprise I didn't have a clutch still.

Is it even possible that the booster is bad and causing the problem? I think if the booster is bad you would just have a stiffer clutch pedal.

[PapaSmurf2k3]

There's extra rods and linkages and junk in the booster. If its not right, you'll know it.

Sounds like it would just be easier to swap out all the crap for a manual master.

[evildky]

Lets start at the beginning. Why did you replace your master and slave? Did you replace the clutch only to find this issue then decided to replace the master and slave? I got a bad PP once, the PP they sent me simply was built with too much resistance, instead of the PP releasing it was just bending the tines. I would not mess with the booster, unless you or someone else monkeyed with it it should be correct.

[LEMHEAD16]

From the beginning.....

Rebuilt engine and new turbos, clutch worked fine before I pulled engine.

Replaced engine with same clutch, PP, and flywheel because they were in nearly new condition and after market parts, also replaced stock clutch lines with Z1 braided stainless hose.

got car running and driving for a few weeks, took it on a 600 mile road trip. Clutch started to get lower and lower during the trip. Parked it over night and when I went to drive it the next day I had no clutch pedal and car would not go in gear. Bled the system again but still had no clutch.

Replaced the slave cylinder and bled system. Still no clutch

Replaced master cylinder and bled system. Still no clutch

Played with clutch pedal adjustment, even though it appeared previous owner had adjusted it according to write up online. Adjusted fully out and fully in makes no difference, still no clutch pedal.

Vacuum tested clutch booster, holds 15mm vacuum for 30 minutes. Which leads me to believe there is nothing wrong with the vacuum part of the booster.

At this point I thought I might have broken a spring in the clutch disc or bent the clutch fork, there was a lot of side to side and back and forth movement in the clutch fork.

Pulled transmission, nothing visibly wrong with clutch disc, PP, or fork. Replaced them all with new parts and a 350Z cast clutch fork and chromoly pivot ball. Still no clutch.

If I use a ratchet strap to pull the clutch fork back I can engage the clutch and put the car in gear with engine running, but the hydraulic system is not pushing hard enough to move the slave cylinder hard far enough.

I know it sounds like there is air in the system but I've bled the s*** out of the system and there is no air coming out. I've used the 2 person pump method, a mighty vac, and gravity bled it. With the Z1 braided line there is really only two places air could be entering the system, at the master cylinder and the slave cylinder, neither seem to be leaking any fluid or sucking air.

[RubyRed300ZX]

I'm late to this party. I feel your pain here. I have the exact same problem. I lost all clutch pressure about a month ago. Replaced the Master and the Slave. Have gone through 1-1/2 quarts of fluid bleeding it and no improvement in clutch pressure. To add some help here. Mine is a convertible; hence, it is an N/A. Therefore, no vacuum assist for the Master. When i say the same problem, the symptoms are exactly as you describe right down to the Slave pin moving only a 1/2" while depressing the clutch. Mine is stock with the fender bleed. Trans and everything was working fine. But, I lost all fluid on a cold (10 degree below zero day within a half mile of the house). Probably lost it through the Slave. Decided to replace both the Slave and the Master because of the age of the car.

I'm not a novice under the hood of a car by any means. And, I've owned mine since it was new (so, yeah, I'm older than dirt itself). I finally threw in the towel though. Called my son-in-law. He and a couple others have a performance shop for VW and Audi's. He's a Certified Master Tech for Audi and also Crew Chief for a Porsche Team. We spent an hour and a half on it one night last week. No change in the results. I need to do another plenum pull on it to replace the rubber cushions on the intake valve covers. So, we just left it as is with the thought of re-plumbing the damn thing when the plenum is off and the top side stripped down. It is a PITA to bleed because they used the same parts from the right-hand drive cars; and, they merely moved the Master to the left-hand side.

Back to the problem. I think it's the Master or the Slave that's bad. Wouldn't be the first time I've had problems with brand new parts that turn out to be defective. In this case, I think it's the internal seal on the piston. The piston has two seals. One on each end. If it was the outer seal, it would be leaking fluid. You'd be able to see it leaking. The inner seal on the other hand would not leak out fluid. It would just create a condition where the piston would merely push past the fluid like a submarine in the water. It wouldn't build pressure until the second seal (outer one) held its seal and started to push fluid. Hence the 1/2" of stroke? I already have another new Slave (forgot it was sitting in my collection of parts when i started this). My plan is to install the other new slave. See if that changes things at all. If not, pick up another Master and install that one. I really think it's the Master and a bad inner seal that is the problem. I'm going to look for a new Master that is not made in Taiwan. In the metal-working industry, the Taiwanese are well known to have their crap made in China and then shipped to Taiwan and labeled "Made In Taiwan." Thus the new Made-In-Taiwan Master I put in is highly suspect. Though originally I planned to re-plumb the mess under the hood, I guess because there are two of us with the same problem, I'll install the 2nd Slave and Master as mentioned in the next week without re-plumbing. I'll let you know the results.

[PapaSmurf2k3]

If I use a ratchet strap to pull the clutch fork back I can engage the clutch and put the car in gear with engine running, but the hydraulic system is not pushing hard enough to move the slave cylinder hard far enough.

It sounds like you just answered your own question. You aren't getting enough throw. The only things that can affect that are pedal travel/adjustment (which you said was checked and good), air in the system (which you shouldn't have by this point), bad master (which you would be able to feel), wrong slave cylinder (rod not long enough or something), or the booster/internal linkage.

[PapaSmurf2k3]

yeah if there's any damper boxes, bypass those evil sons of bishez.

[LEMHEAD16]

If I use a ratchet strap to pull the clutch fork back I can engage the clutch and put the car in gear with engine running, but the hydraulic system is not pushing hard enough to move the slave cylinder hard far enough.

(rod not long enough or something),

I've also tried making the rod as long as possible without bottoming out the slave with no success.

[PapaSmurf2k3]

Is it an adjustable rod or something?

I just remembered too, if the wrong throwout bearing is in there (meaning too skinny), it wont work either. The throwout bearing acts a shim so to speak.

[LEMHEAD16]

I just used some 1/4" rod I had laying around to make several longer length push rods.

Fairly certain it's the correct TO bearing.

[evildky]

OP, This is a TT, which has the remote bleed valve on the inside forward portion of the passenger side inner fender, I assume you bled there too right? Some people overlook this little step.

Rubyred and OP, sometimes it helps to clamp the slave compressed, and have a person press the pedal as you crack the valve closing it as they reach the bottom, doing this a couple of times can sometimes chase out a trapped air bubble, also smacking the master and slave with a wrench before opening a valve isnt a bad idea.

I did have a napa reman brake master once that was simply missing an internal seal, no matter what I did I could not build brake pressure, then I took the danged thing apart!

[RubyRed300ZX]

Open to any advice at this point. Have tried all the following:

Bled from both the fender and the slave.

Gravity bled.

Clamped the slave with the pin fully retracted, locked down with a very large C-Clamp.

Disconnected the slave from the trans, to invert it while bleeding so that the bleeder was above the banjo bolt.

Vacuum bled it from both bleeders.

Used an offset (curved) syringe to push fluid through the opening at the bottom of the Master reservoir.

Used the syringe to suck fluid from the hole at the bottom of the reservoir on the master.

Checked the new slave to ensure that the pin is the same length as the original OEM.

Bench bled the Master and the slave a second time and reinstalled.

Bench bled the master while somewhat installed on the car (but still able to invert it by about 45 degrees).

Reverse gravity bled from the fender bleeder back through the Master reservoir.

No improvement from any of this; no air bubbles; just clean new fluid; and only a 1/2" of travel to the slave pin.

[RubyRed300ZX]

I haven't proceeded any further yet on this. Wife has other things she wanted to do today besides push on the clutch pedal while I roll around under the car. Though, I was thinking about my posts; and I'm not sure that I was being clear enough. I wasn't trying to hijack the thread. I was trying to note that mine is a N/A, his is a TT, and while he had his engine and trans out, I did not.

Yet, the symptoms on both cars are absolutely identical. Thus, he may want to focus on what is identical on the cars rather than any parts not the same. The trans wasn't out on mine. Thus, unlikely it's the fork or throw-out bearing etc. The N/A has no booster; so again, it's not likely that's the issue either. Though the master cylinders have different part numbers, it appears that the parts are only different due to the shaft and yoke that connect to the clutch pedal.

I believe the slave cylinders are the same for the N/A and the TT. The plumbing of the hard lines and the second bleeder to the fender location are the same. With no fluid leaks from the piping, the manifold which splits the line into two lines to the slave and also the bleeder on the fender, it just leaves three things: the Master, the slave or air in the lines. Neither one of us appears to have air bubbling out. So hence, my comments of a brand new Master and brand new Slave with one of them, or both I suppose, being defective.

[PapaSmurf2k3]

Sounds similar to the BS that comes on 240s.
We just bypass everything such that there is a hardline directly from the master to the slave.

[LEMHEAD16]

I replaced my TT Clutch pedal and booster assembly with a NA non boosted master cylinder and everything works perfect! My guess is the booster was bad causing the original problem. I have a Z1 clutch kit in it and the pedal pressure isn't bad at all. Glad to finally have this issue resolved after two months of banging my head on the wall.

[evildky]

The booster only reduces the pedal effort needed. You either had air in the system you got out when you replaced the parts of you had a bad master and new master was the fix. Glad you worked it out but the booster was not the issue.

[LEMHEAD16]

I know that's what logic dictates, but I tried 3 master cylinders and 2 slaves with the boosted set up and am 99.9% certain there was no air in the line.

When I pulled the booster out the rod that pushes the master cylinder had tons of lateral play in it and fell out of the booster when I turned it over. I know the vacuum part of the booster was functioning because it held vacuum for 30 minutes, but I think the linkage inside was broken. Right or wrong it's fixed. I hate throwing parts at a problem to try and fix it and usually diagnose and test the failed part before replacing but the booster was the only part in the system that had not been replaced.