Hydraulic Clutch

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Turbo_Manx_Maniac

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I have a 9" stage 2 clutch, 6 puck I bought from Outfront in my Manx, it had a CNC 5/8 Master and the normal CNC pulling slave. I've had the clutch fail (hydraulics) several times with no pedal, so I decided to replace it all after rebuilding the master & slave several times.

As CNC doesn't exist anymore, and I want new rather than rebuilding yet again, I decided to try the Jamar 5/8" master and slave. As I hoped, it all installed very easy. All the bolt holes and dimensions matched up to the CNC. The issue is that even though I matched the master size, the pedal is much harder that it was with the CNC. It feels more precise, meaning there is not much slop in feeling where it starts to pull, and this may just be due to being fresh fluid and bleeding. I noticed there is no master options for the slave, and there is no smaller master. This is gonna give me some leg pump, I do some rock climbing and grubbeling, and I work the clutch a lot. 

Also, there is some dead pedal I can't get rid of, meaning I can't adjust the clutch to start at the beginning of pressing the clutch pedal. If I adjust the slave so there is a lot of tension on it, the old slave would start pulling it as soon as I touch the pedal, this one has an inch or so of travel before it does anything. If I lengthen the rod, it just pushes the pedal up higher in the resting position, the dead space is unchanged. The slave doesn't move in that first inch or so of travel. When I adjust the arm so the throwout bearing isn't quite touching, there is about 2-3 inches of travel before I feel the pull of the pressure plate.

Anyone else have this experience? Have any ideas to make it a little easier? Like a longer clutch arm at the transmission (091)?

 
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Well I already used my "smart advice" for this 30 years so I got nothing for you here. I'll chime in....in 2032 🙂

 
Thoughts on taking the clutch lever arm and extending it 1/4 - 1/2" to reduce pedal effort?

 
1/2”. Would be good. I don’t think you would notice 1:4”. Do you know if Jamar has a different slave bore size than Cnc? 

 
Turbo_Manx_Maniac said:
Also, there is some dead pedal I can't get rid of, meaning I can't adjust the clutch to start at the beginning of pressing the clutch pedal. If I adjust the slave so there is a lot of tension on it, the old slave would start pulling it as soon as I touch the pedal, this one has an inch or so of travel before it does anything. If I lengthen the rod, it just pushes the pedal up higher in the resting position, the dead space is unchanged. The slave doesn't move in that first inch or so of travel. 
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If I read this correctly, you are saying the clutch pedal moves about an inch before the slave cylinder at the trans starts to move?

The first obvious issue would be air in the line, which is compressing in the first inch of pedal movement until it compresses enough to push the fluid to against the slave cylinder. Bleed it out a bunch and see what happens. Bleeding is relatively easy to ensure this is not the problem.

Another issue could be o-rings in the master. Don't believe that just because it is brand new that there is not some sort of defect in the seals, or has scored piston/bores. Any of these can cause blow by of the fluid under compression. 

If you are absolutely confident there is no air in the line and parts are in excellent condition, the next thing I would be interested in is if the master cylinder piston is properly positioned in the bore to seal off the reservoir as soon as the piston starts to move with the pedal actuation. Meaning, the piston could be sitting back from the bore in a way that allows it to push fluid back into the reservoir until the piston seals the bore from the reservoir. Does that make sense?

I have never experienced that myself, or dealt with anyone that has. It's just a thought as I think about the mechanics of what you are describing. 

 
Sean@Weddle said:
If I read this correctly, you are saying the clutch pedal moves about an inch before the slave cylinder at the trans starts to move?

The first obvious issue would be air in the line, which is compressing in the first inch of pedal movement until it compresses enough to push the fluid to against the slave cylinder. Bleed it out a bunch and see what happens. Bleeding is relatively easy to ensure this is not the problem.

Another issue could be o-rings in the master. Don't believe that just because it is brand new that there is not some sort of defect in the seals, or has scored piston/bores. Any of these can cause blow by of the fluid under compression. 

If you are absolutely confident there is no air in the line and parts are in excellent condition, the next thing I would be interested in is if the master cylinder piston is properly positioned in the bore to seal off the reservoir as soon as the piston starts to move with the pedal actuation. Meaning, the piston could be sitting back from the bore in a way that allows it to push fluid back into the reservoir until the piston seals the bore from the reservoir. Does that make sense?

I have never experienced that myself, or dealt with anyone that has. It's just a thought as I think about the mechanics of what you are describing. 
Click to expand...
"Meaning, the piston could be sitting back from the bore in a way that allows it to push fluid back into the reservoir until the piston seals the bore from the reservoir."

This is it exactly, with the cap off, I can see the fluid streaming upward for that first 1" of pedal travel. I am thinking of removing the piston and seeing if I can shim it so it just closes the hole in the master. Can't see a way of holding the pedal rod in a certain position without affecting the pedal position.

I'll probably try and contact Jamar first and see what they say.

 
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John@Outfront said:
1/2”. Would be good. I don’t think you would notice 1:4”. Do you know if Jamar has a different slave bore size than Cnc? 
Click to expand...
Good question, I only see "Slave" on the various websites, no mention of what bore size it is. When I call them about the "dead spot" in their master I'll ask about a slave size option.

 
Sean@Weddle said:
If I read this correctly, you are saying the clutch pedal moves about an inch before the slave cylinder at the trans starts to move?

The first obvious issue would be air in the line, which is compressing in the first inch of pedal movement until it compresses enough to push the fluid to against the slave cylinder. Bleed it out a bunch and see what happens. Bleeding is relatively easy to ensure this is not the problem.

Another issue could be o-rings in the master. Don't believe that just because it is brand new that there is not some sort of defect in the seals, or has scored piston/bores. Any of these can cause blow by of the fluid under compression. 

If you are absolutely confident there is no air in the line and parts are in excellent condition, the next thing I would be interested in is if the master cylinder piston is properly positioned in the bore to seal off the reservoir as soon as the piston starts to move with the pedal actuation. Meaning, the piston could be sitting back from the bore in a way that allows it to push fluid back into the reservoir until the piston seals the bore from the reservoir. Does that make sense?

I have never experienced that myself, or dealt with anyone that has. It's just a thought as I think about the mechanics of what you are describing. 
Click to expand...
I agree, something has to be wrong.

I have a 9" with a stage 3, and with a 5/8 master it was soft. I ended up going to a .70

 
In my old VW powered car I started with a 5/8" master and ended up with a 3/4" because the 5/8" was not moving enough fluid. On my current car, I just installed Jamar masters to replace my old CNC brake masters that quit working. It took me quite a while to get all of the air out of the masters which may be playing into your issue as stated a couple posts up.

 
I called Jamar twice, the second time I was able to get some info and things to try.

They think the CNC slave was a 1" and the Jamar is a 3/4". So my only option is extending the arm to get more leverage.

Going to have to figure out how to keep the piston pushed in a bit to get rid of the dead pedal.

 
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