R34 clutch

[RTJ]

Clutch pedal on my 34 is working about75mm from floor.

Fluid level has not changed , Rubber boot on the slave is reasonably compact which indicates(to me )that the throwout/clutchplate and fork are probably ok.

BUT,,when I check for free play at the clutch fork it seems to be pressure-ised. ..So I can force the slave piston back and release the throwout bearing .

But when i release it , the cylinder pushes the fork straight back against the bearing.

 

[GTSBoy]

It's either a hydraulic problem (master or slave internally bypassing) or a mechanical problem in the clutch itself (broken springs/fingers/rivets/whatever). The last part of your symptoms make it sound like the clutch is broken.

[RTJ]

So I can push the piston back into the slave cylinder and it forces itself back out...As if you pushed the pedal ..

The force is not coming from the throwout fork..

And  ,,,the rubber boot on the slave is quite compact,, not extended (indicating wear).

Fluid level in the master rises accordingly and there are no air bubbles.

There is a larger diameter ""loop"" attached to a 4 way splitter (like on a diff housing to split L and R brake lines)..

It is located near the slave cylinder and the clutch line goes in and out of it with the loop connected to 2 of the 4 ports,,, I have no idea what it does..

At a guess it adds capacity to the circuit , also has a bleeder..

Any valving in this device or possibility of air in the loop ?.

The slave shouldn't be pressureised.

Would like to fix this without adding helper springs to the fork.

 

 

 

[GTSBoy]

24 minutes ago, RTJ said:

There is a larger diameter ""loop"" attached to a 4 way splitter (like on a diff housing to split L and R brake lines)..

It's a pulsation damper. Shouldn't cause any problems. When people put braided clutch hoses on this is usually removed and the pedal feel changes, but that's about it.

Your second, more complete description does make it sound like the master has pressure on it. That would either be because something is wrong at the clutch pedal (maladjusted, or something worn/broken, like the pivot or the pedalbox itself), or there is a problem in the master such that it is retaining pressure and not relieving it.

[RTJ]

Thanks for your patience,,,

Pedal has freeplay at top stroke and the pivots are all good ..

Master refills when the piston is forced in (we 're talking 2 thumbs medium pressure.).

This to me equals no pressure should stored.

Has to be a spring somewhere.

For full clarification ,,The car is modded in japan with all mods being high end names on a cleanskin car.. and ive owned it for about 8 years with no probs.

Would a spring be behind the slave piston for Jap street ?

 

 

 

 

 

[GTSBoy]

How much force pushing the slave piston back out? About what you'd expect from the rubber boot pushing back?

[RTJ]

So, to save guess work I pulled the slave out and apart...

Bingo,,,a big spring...

I don't think it should be there...

Is this factory or a mod ?. I suspect it loads the throwout bearing full time , which to me is a no..

I can't see the sense in replacing the clutch assembly only to have it fry again.

 

[RTJ]

Guess I've got to inspect the internals of the bell housing to check for broken counter springs that may act against the one in the slave..

So miles from nowhere, and with no successful replies i've managed to knock up an adjustable gearbox jig..

Apart from the front half shaft caps on the uni's being retained by press marks and not C clips; all looks normal.

Box comes out tomorrow,,Just hope its for a good reason and not an effort in futility..

I'd like to  think some one would have seen inside a few standard 34 slave cylinders....

Apparently mine is unique..

 

 

 

[GTSBoy]

Dunno. R34 turbo slave cylinder is a pull clutch, not push. I've not handled one.

RB30, RB20, RB25 (vanilla) are all push clutches. I've got a vanilla 25 box, and when I needed a new slave I just threw the old one in the recycling bin!

Are we looking at a pull clutch on your car?

[BK]

The slave pictured is definitely a pull and not unique, same as 33gtr, 34gtr and 34gtt.

They retail for about $120. I have one for $60 if you need it.

[RTJ]

Learning a lot as I go..

Mostly by reading on this site.

It's a pull type and i've got the lowdown on fork removal to let the gearbox come off,(stopped me today).

The main and original question for my peace of mind still remains.

Is that spring supposed to be in the slave cylinder ?.

Just can't get my head round the idea of a throwout bearing being under constant pressure.

It may be obvious (or not), once the box is off and I get my head round the inner workings, but that's now delayed till next weekend.

 

Yes or no on the spring and I will be happy ?.

 

 

 

[BK]

Yes I believe the spring is supposed to be there, just to take up any slack the in the piston rod to release fork when release fork is against it pushing it in. That spring is not going to do jack shit against a release fork as far as trying to depress a clutch, or put any load on the bearing. much more pressure is required to actually disengage the clutch than that spring can achieve.

[RTJ]

A big thanks BK,,. Gives me a positive amount of re-assurance that i'm not trying to repair a poorly modified setup.

Box comes out on the weekend and then I get my head around the pull clutch release design in the flesh.

 

Will reply once I've learnt !!!.

[BK]

I didn't pull any slaves apart as I didn't want to compromise any sealing but, Dude I literally got a brand new push slave today, and have a pull slave that's done about 50k km. Both when piston depressed pop straight back out without any hydraulic hook up, therefore there is springs in them just to pop the piston and push rod out to take up free play.

The clutches themselves are not hard to understand when you see them...