Clutch not fully engaging in S14 with RB25det

[240z4u]

Iam going to be taking apart my S14 sometime in the near future but was wondering if anyone else had simalier issues.

Basically the clutch engages at the very end of the pedal travel. I have tried adjusting the master cylinder. I have also put in a new rb25 slave cylinder and s14 clutch master. I also checked my hardline for crimps or tight bends that would impede fluid flow.

I am still having the same issues, clutch engages pretty normally from stoplights, but at any boost above 7psi the clutch holds then all the sudden lets go. It does not start slipping, but all of the sudden lets the motor rev high with no accelleration.

For some reason I noticed this really bad after driving many hours on the highway to indianapolis. I did NOT ride the clutch at all, it seemed like pressure built up as I was driving. The pedal got very stiff, and it got more normal if I held the peddle down or pumped it a bit.

It does not seem to matter whether or not the car is cold, but it slips less when the car is cold. Logical since the clutch has not heated up yet either. I used the XTD 300zx clutch, bolted up like a charm with no issues. I also used a 300zx throwout bearing. Everything bolted up normally and I did NOT have to pull the halfs together with the bolts.

Any thoughts/suggestions would be great!!

Thanks - Evan

[Joe]

thats very strange its like 2 opposites.

usually when it engages at the bottom of the pedal travel (floor) you will have shifting problems, like it wont go into gear, grinding, etc. and if it engages at the top of travel, you can get slipping problems because the clutch is like its always being pressed.

first, make sure everything is bled properley (even the gay little dampning hardline that runs near the slave)

if that dosent help id look at your master cylinder.

[240z4u]

I know it does not make ANY sense. My master is new, and the old one did the same thing!!

I will give it another bleed and see if its any better. I doubt it though.

Another question, where in pedal travel does your clutch engage? Maybe mine is normal but the clutch is contaiminated with something.

Still does not explain the funny release point (almost at the end) and the pressure that builds in the system on the highway. I wonder if the pressure is'nt a heat thing from the engine compartment. Also, it was only about 50 deg ambient when this happened on the highway.

Evan

[dekand]

well my clutch doesn't engage like the ka one did but ive had my car driving for a good 6+ months now without problems, i adjusted some slop in the pedal and it feels fine to me now but its still a short throw compared to other cars ive driven... but it doesn't slip at all so im assuming its fine....

anyways i took off the damping part of the clutch hard line because we just could not get it to bleed properly and every 240 guy i talked to said to take it off so thats what i suggest to you, we had it bled perfect in 5 minutes without that peice of crap...

my friend had the same problem as you i believe, personally i think its because he re-surfaced the flywheel wrong but you never know, did you get yours re-surfaced?

[Darius]

How do you improperly resurface a flywheel? I had mine resurfaced, but have no idea how much they took off.

[240z4u]

I forgot to mention that I took off that goofy extra piece that everyone loves so much and makes the clutch hard to bleed.

I did have it resurfaced by my machine shop, they have done about 5 other flywheels for me and they do great work so I am pretty sure thats not the case.

Thanks guys - Evan

[dekand]

well what i hear is the rb25 flywheels have a step in them, not sure if thats the right term anyways they aren't flat basically so if they aren't surfaced in the same way, basically if they make it flat the clutch will fail prematurely... at least thats what ive been told.

[240z4u]

Yep, my flywheel is machined with a step! It was all done according to the information that the machine shop had for a 300zx flywheel.

Evan

[Darius]

hmmmmm I had mine resurfaced and I think they might have taken the step out of it even though I told them to follow the 300ZX specs... I'll have to check first though.

OK. so I called up the shop that resurfaced my flywheel and they said that the 90-96 300ZX NA flywheel has a 0.003" step in it which equates to a hair thin step. They machined mine down to that and you can only feel the "step" with your fingernail so I called them up and they told me to bring in my clutch to see what they could do. I don't know what they can do to fix it, but isn't the critical dimension the one between the pressure plate and the backside of the clutch?
Modified by Darius at 5:46 PM 1/16/2006