Hydraulic clutch question

[rjbaren]

If it is not one thing it is another.  I went for a drive early this morning, I couldn't help it I wanted to let her loose and ran it up to 100 for a second or two and it felt pretty good.   
But during the drive I was doing some easy two lane cruising in 4th gear and I went for a downshift and my clutch pedal had almost no resistance.  Eye opener! I let it up and immediately tried it again and it was back to normal.  This happened again near the end of my drive.  It also happened one day last time I drove but I thought it was just a one time thing.   
I have the cable still attached to the pedal and tucked in the frame by the battery so I think I will make sure I am able to reattach the cable if the Hydraulics fail.
Any idea what may be happening?  It has only been about 500 miles with the hydraulic clutch installed. 

[Pfreen]

It could be heat from the headers boiling the fluid.  If I remember, it is located near the shifter center bearing, close to the exhaust header.  Other than that, I have no clue.

[rjbaren]

Thanks Pfreen, the slave cylinder is actually next to the bell housing.  It is quite close to the header down pipes.  But I think if the fluid were to boil why would it be usable again immediately?  I would think it would continue to be "on the boil" while the car is still driving along.  I am wondering if somehow air got in the line or if one of the two cylinders is beginning to fail.  If the boiling theory is correct, what would prove a better solution for the heat, wrapping the header or removing it and have it coated?

[BDA]

It looks like everything is far enough away from your headers. I assume you properly bled the system e.g. pressure bleeding, or even what we used to call the “tube and coke bottle method.” Having someone pump the pedal and then cracking the bleed screw (without a tube that runs into and below the level of some fluid) will not cut it. Could there have been a possibility that air came into the system via the bleed screw? Teflon tape or a product link EZ Turn on the threads of the screws should take care of that. Lastly, I wonder if you need to bench bleed your master cylinder. I must admit that I don’t fully understand why you need to bench bleed a brake master but know that it greatly improves your chances of success when installing one. Maybe the same principle applies here.

Good luck!

[TurboFource]

Are you getting all the air out? Bleed screws looks to be pointed sideways instead of straight up....or does it just look that way in the pic?

[GavinT]

Agree with Turbo - I'd want the pressure inlet on the side and the bleed at the top.

Maybe JB could shed some wisdom if he sees this.
I recall he mentioned his pull slave uses O-rings instead of traditional lip seals and that they don't last as long.

[jbcollier]

Had the very same thing happen to me.  Took a wee bit of head scratching to figure it out.  The Girling type clutch master cylinder automatically adjusts the clutch system’s free play.  This doesn’t work well with the pull slave.  Engine vibration will sometimes cause it to lose the auto clutch adjustment and the pedal goes to the floor but works fine with the next pump, and fine after that for a long while.

You need to adjust almost ALL the free play out with the slave cylinder’s adjustable pull-rod.  Then it will be fine.

[rjbaren]

Thank you.  I took a close look at the cylinder, and there is one nut on the rod and I imagine that is where I need to make the adjustment.
It's nice to know that the new clutch cable is tucked in the frame with the two nuts.  Plus I keep the little piece that holds the cable to the fork on the glove box so in case of total failure I should be able to let things cool down and move the cylinder and attach the cable and be on my way.

[BDA]

Always good to have a backup plan!

[rjbaren]

I have driven the car a few more times.  The clutch behaved fine until last night where it again went to the floor. 
Today I made the adjustment which was in effect to shorten the rod by threading the Heim joint closer to the cylinder.  I have only started the car and moved it back and fourth in the garage and it seemed fine for that.  I will take it out tomorrow for ride and see what happens.  Too hot and too much traffic right now.
But I do think shortening the rod is the way to remove the free play in this pull system. 

[jbcollier]

Yup, correct.  You can pull the clutch fork and feel when the release bearing hits the clutch.  You want just an 1/8” or so of “play”.

[rjbaren]

I have made two adjustments to the clutch.  So far it hasn't made a difference.  Every once in a while the pedal has no resistance and then works fine. 
Tonight I have adjusted it as far as I am able, there are no more threads on the rod.   I also had my wife come out to the garage and we bled the slave for good measure.  Tomorrow morning, weather permitting, I will go for another drive and see if there is any improvement. 
Two things I think about. 1, there is no return spring, maybe the cylinder is not fully retuning and that is why the pedal goes to the floor.  2, maybe one of the cylinders is going bad.  For about 450 miles there was no problem at all, this is kind of a new development. 

[rjbaren]

I drove the car again this morning.  I drives so well with the exception of the clutch pedal.  It works nearly all the time.  I have noticed when it loses its pressure it is after driving steady in a gear for a while.  So, driving along in 4th or 5th for 5 or so minutes and then seeing a traffic light ahead I will downshift but the pedal has no pressure.  1 extra pump and then it is back to normal. 
I don't believe there is any more adjustment left unless I shorten the rod.  I still wonder about a return spring.  Is it possible the cylinder is creeping and therefore losing pressure while driving along?
Its disconcerting to feel the pedal with no resistance.  I am afraid one of these time it may not came back after that
"second pump".     

[jbcollier]

Disconnect the slave and pull the clutch fork until it rests against release bearing hits the pressure plate.  Note the position.  This is where the clutch pull rod has to be adjusted to, less an 1/8”.

[rjbaren]

OK, I think I got it.  I removed the rod end and removed a half inch off the rod end and put it back on.  The rod itself doesn't have much thread so in my opinion, better to cut the rod end.  The same amount of threaded rod will screw into the rod end as before.  Now the cylinder is where you say it is supposed to be with 1/8" of free play.  Before, I had it adjusted all the way down, so now another 1/2 of travel has been removed.
I also rotated the cylinder 90 degrees so the bleeder is now at 12 o'clock.  I hope to bring back my wife to bleed it a little more and maybe get a drive in tomorrow.