R154 clutch pedal issue

[joey]

Hey guys, need some advice.
When i give the chaser some stick and change gears, the clutch pedal stays 3/4 pressed down. If i push it down again i can change gears but it still stays in the same spot. If i slide my foot underneath the pedal and push it up then it works fine again until i give it some stick again. It's a stock clutch (jzx100) and still feels like it has plenty of meat on it. I've bled the clutch from the slave and inspected the pedal mechanism and all is fine.
Anyone got any ideas what it could be?
Just to clarify if i drive it normally its perfect, only when i give it some does it stay down.

Cheers, Joe

[Dale]

Are the lines secured to the chassis/gearbox properly (ie. as per factory) or only bolted on to the slave cylinder?

[joey]

Yep all lines are as per factory exept one which is braided and goes from the slave to one of the links from memory, made sure its all tight and no air leaks in it though.

[Dale]

It does sound like a hydraulic problem, I was thinking when you give it stick and the engine twists/moves it might have been upsetting the line somehow. For the pedal not to be coming back up the fluid needs to be going somewhere other than back up the line as the clutch fork pushes the piston in the slave cylinder back in - or the clutch fork isn't pushing the piston back in fully. But in that case you'd more than likely be getting clutch slip...

Is the master or slave leaking at all?

[joey]

Yeah i was thinking along the same lines of something to do with the slave cylinder piston not being pushed in properly, maybe a leaking seal or something but then i realised this would be happening all the time, not just when its under heavy load.
Master & slave aren't leaking from what i can see.

[manny]

I had this happen on a poorly adjusted as well as a worn master cylinder running one of my R154s.
Where is your clutch pickup point ? ie low/mid/high pedal position
Have you adjusted the master's pushrod to pedal length?
How old are the master/slave cylinders?

[allencr]

the clutch pedal stays 3/4 pressed down.

Did it get pushed down normally and then return to 3/4, or did it have 1/4 freeplay & only then have resistance down to the floor?

I think it's 2 problems, the MC piston isn't returning and the slave's piston is getting pushed in.
The MC doesn't return because of a bad spring, bad bore or the pedal linkage is binding.
The slave is getting pushed in by crank end float.

[joey]

I had this happen on a poorly adjusted as well as a worn master cylinder running one of my R154s.
Where is your clutch pickup point ? ie low/mid/high pedal position
Have you adjusted the master's pushrod to pedal length?
How old are the master/slave cylinders?

Clutch pickup point is around the middle, still has plenty of travel and bites well. Nope havnt adjusted the pushrod to pedal length.
Master and slave are as old as the car as far as i'm aware, which is 1996.

Did it get pushed down normally and then return to 3/4, or did it have 1/4 freeplay & only then have resistance down to the floor?

It gets pushed down normally as per any clutch change but just at a higher rpm. To clarify, once the pedal is realeased it only comes about a quater of the way back, it has a little bit of resistance from here to the floor but generally doesnt want to change gear until the rpm drops back down or i have pushed the pedal back up.

Going by the exploded diagram for the master found here:
http://www.toyodiy.com/parts/p_J_199...TMVZ_3103.html
and the slave:
http://www.toyodiy.com/parts/p_J_199...TMVZ_3105.html

I think i'll order the "04311 CYLINDER KIT, CLUTCH MASTER" and "04313 CYLINDER KIT, CLUTCH RELEASE ". This should cover all bases whether it is the master or the slave.

Thanks for the advice so far guys.
Cheers, Joe

[manny]

Before you go spend any cash, try adjusting/shortening the rod length behind the pedal by a turn or two and see if it improves.
Also compare cost of the cylinder rebuild kit vs a new complete cylinder - it wasn't all that much of a saving when I costed them up in the past.
Age is also against you as they are consumable items - I've been through 3 masters in 10 years on my factory 5 speed JZZ30 Soarer, but I have also contributed to their demise with harsher/heavier multiplate clutches running off braided lines.

[acmtt]

Hey Joey , i shoulld have had a closer look at it when you were over. I still think the most likely culprit is a worn master cylinder, however try flushing the fluid in it first. Just put a fresh batch of Dot 4 in it.
Its a cheap, easy thing to rule out, i have heard of a case similar to this. Not sure why, whether it was just old fluid or what.

[AAAAGZE]

install bigger return spring on pedal

[joey]

Hey Joey , i shoulld have had a closer look at it when you were over. I still think the most likely culprit is a worn master cylinder, however try flushing the fluid in it first. Just put a fresh batch of Dot 4 in it.
Its a cheap, easy thing to rule out, i have heard of a case similar to this. Not sure why, whether it was just old fluid or what.

Not a bad idea i guess, ive bled it with fresh dot 3 but havnt got rid of the old stuff completely.

install bigger return spring on pedal

Its already got a grand daddy of return springs on there lol. and isn't binding