Clutch Slave Pressure Relief Valve and Adjusted Clutch Master

shadow

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I noticed a few drops of brake fluid on the aluminum pan right below the clutch slave cylinder. I have done the following to my clutch system:

1. CMC adjustment for maximum fluid displacement. See video in the link below:
https://www.civicx.com/forum/threads/type-r-tranny-issues-still.28440/page-11#post-482392
2. Clutch delay valve removal
3. PRL clutch line

With modification #1 above, everything was fine.

After mods #2 & #3, I noticed the droplets. The first thing I did was to check the clutch line and delay valve removal sides. Both were clean and dry. The delay valve side had a new EDPM o ring because the original one ripped. Further inspection showed a pressure relief valve below the slave cylinder to be the source of the fluid. That means the slave stroke has maximized and excess pressure vented out.

The delay valve only delays the fluid flow, but the volume moved by the master cylinder is the same. That can't be the problem.

That leaves the clutch line. I'm guessing with the OEM rubber line, the excess pressure expands the hose. With the PRL braided line, it doesn't expand so out the relief valve it goes.

Since then, I've reduced pedal travel by half a turn on the clutch pedal stopper bolt. The master cylinder rod was adjusted accordingly. It was still venting out some fluid.

I will try to adjust it some more and report my findings here.
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Centripetal

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I noticed a few drops of brake fluid on the aluminum pan right below the clutch slave cylinder. I have done the following to my clutch system:

1. CMC adjustment for maximum fluid displacement. See video in the link below:
https://www.civicx.com/forum/threads/type-r-tranny-issues-still.28440/page-11#post-482392
2. Clutch delay valve removal
3. PRL clutch line

With modification #1 above, everything was fine.

After mods #2 & #3, I noticed the droplets. The first thing I did was to check the clutch line and delay valve removal sides. Both were clean and dry. The delay valve side had a new EDPM o ring because the original one ripped. Further inspection showed a pressure relief valve below the slave cylinder to be the source of the fluid. That means the slave stroke has maximized and excess pressure vented out.

The delay valve only delays the fluid flow, but the volume moved by the master cylinder is the same. That can't be the problem.

That leaves the clutch line. I'm guessing with the OEM rubber line, the excess pressure expands the hose. With the PRL braided line, it doesn't expand so out the relief valve it goes.

Since then, I've reduced pedal travel by half a turn on the clutch pedal stopper bolt. The master cylinder rod was adjusted accordingly. It was still venting out some fluid.

I will try to adjust it some more and report my findings here.
Interesting. I have the same setup and have not noticed this. However, if it leaked some brake/clutch fluid, it will easily evaporate and I would have missed it. Maybe I can put some Dykem on the pan; I'm pretty sure brake fluid will dissolve the Dykem.
I did have issues getting the SS line properly placed because of the lack of anti-rotational mating/mounting. The SS line would gradually move over and rest on the transmission cooler.
 
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shadow

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Interesting. I have the same setup and have not noticed this. However, if it leaked some brake/clutch fluid, it will easily evaporate and I would have missed it. Maybe I can put some Dykem on the pan; I'm pretty sure brake fluid will dissolve the Dykem.
I did have issues getting the SS line properly placed because of the lack of anti-rotational mating/mounting. The SS line would gradually move over and rest on the transmission cooler.
Thanks for the heads up. I will check mine.
 

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Interesting info. I bought a PRL SS clutch line years ago but never actually installed it.
 
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shadow

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Centripetal: I checked my clutch line and it was ok. Here is how I installed it:

1. Connect both ends to the hard lines, but do not tighten.
2. Make sure braided line is in a relaxed state, meaning it is not fighting any twist or bend in the line.
3. Tighten carefully, making sure braided line doesn't twist too much.

HTH
 


Centripetal

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Centripetal: I checked my clutch line and it was ok. Here is how I installed it:

1. Connect both ends to the hard lines, but do not tighten.
2. Make sure braided line is in a relaxed state, meaning it is not fighting any twist or bend in the line.
3. Tighten carefully, making sure braided line doesn't twist too much.

HTH
Thanks for the follow up but my post was in the past tense.

I should have posted what the issue was. When I was removing the stock line, it was clear I had driven the car in the winter. I ended up needing a crowfoot and a impact gun to get it loose. When I reassembled it, I noticed I had bent the mount a little when I was trying to break it loose by hand. Consequently, when I bent it back, it put a little twist in the line. I fixed it by giving it a 1/8 of turn.

Back to the original topic, I did a test and it does look like Dykem will work.

I thought I should mention when I adjusted my clutch pedal, I put a little pre-load and checked by compressing the slave. I also lubed up the piston and cap when reassembling.
 
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shadow

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I thought I should mention when I adjusted my clutch pedal, I put a little pre-load and checked by compressing the slave. I also lubed up the piston and cap when reassembling.
I did exactly as you.
 

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I might have an extra slave cylinder around. If I do, I will measure the relief valve releases.

I wonder if there is something going on with the relief valve. Every once and while, my hydraulic lift will fail to hold the car up on hydraulic pressure alone. When that happens, I have to remove the check valve and clean it out. What ever causes it is tiny because I have yet to see a particle.

Since I have the same setup, let me know if there is anything you’d like me to try. It just snowed here so it’ll be a couple days or so before I’ll be driving around with the Dykem on the pan.
 
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shadow

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The CMC stroke was reduced a total of three times and relief valve is still releasing some fluid.

I've done the following and none caused fluid to come out:

1. Pump the clutch twenty times and holding it down at times.
2. Leave the car alone for a couple of days
3. Short forward and backward movements in the driveway.

However, a 30 minute drive will definitely show some fluid.

Today I adjusted the CMC rod to stock with the slack and everything. I'll post my results after work tomorrow.

Centripetal: Do you think that once the pressure relief valve opens, the threshold is never as high as it originally was?

If it still leaks, I may do one or both of the following:

1. Reinstall the OEM rubber clutch line
2. Replace with my spare untampered OEM slave cylinder

I'm afraid to trigger the new cylinder's pressure relief valve if it might lower future threshold pressure.
 
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shadow

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With the clutch master cylinder rod and pedal adjusted back to stock, the slave cylinder relief valve is still leaking.

My next move is to reinstall the stock rubber clutch line.
 


Centripetal

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Centripetal: Do you think that once the pressure relief valve opens, the threshold is never as high as it originally was?
Sorry, I've been ridiculously busy. It's completely possible it didn't return and/or seat correctly. It's not something that's intended to be used frequently.

Since I did not design the system, I can only speculate. The relief valve is there as a redundancy to prevent a catastrophic failure. If it vents, and the system "works" without the driver noticing a performance impact, that's considered okay. There is the risk of running out of fluid but that's reduced by "check your fluids at every fill up". Then the driver will eventually note they are filling up the fluid frequently.

I haven't noticed any fluid so far. I'm not sure if I've hit the 30 minute drive mark though.

Are you using Honda Brake Fluid?
 

Centripetal

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No I’m not using Honda Brake Fluid, but still a DOT 3 one.
The Honda Brake fluid has a really high pH 10.3, which I'm assuming is to prevent corrosion. It's boiling point is actually high enough to meet DOT 4 standards but DOT 4 doesn't allow such a high pH.

If you've had it in there awhile, it might be something to consider. If it's been less than a 2-3 years, its unlikely.
 
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shadow

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The Honda Brake fluid has a really high pH 10.3, which I'm assuming is to prevent corrosion. It's boiling point is actually high enough to meet DOT 4 standards but DOT 4 doesn't allow such a high pH.

If you've had it in there awhile, it might be something to consider. If it's been less than a 2-3 years, its unlikely.
It has been in there for only 2 months.
 
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It's completely possible it didn't return and/or seat correctly.
Since the relief valve is a ball and spring type, maybe I can help it a bit. I used a 1" finishing nail's head to push it against the seat. After the first drive, the leak was much less.

Next day, I pushed it in again from different angles. After two short drives, it dry. ?Let's see in a few more days.

Pushing in the ball just means gripping the nail bare hands and pushing, no tools used. I just reached down from beside the DP.

Update: 1/4/21: No leaks from the relief valve. The ball was just improperly seated and pushing it in solve it.
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