Slave cylinder issue/question

[lahrs37]

Hey all,

So I have been having issues with the hydraulic clutch setup from Forte. I have T-5 transmission with a stock clutch and the pedal was ridiculously stiff. Thinking that maybe I made the pushrod too short, I went to remove it and discovered that the slave boot was full of fluid. It turns out that the slave cylinder is overextending past the seal. You can see this in the pictures. I contacted Mike, but I was curious as to whether there is a simple fix to this?

http://i36.photobucket.com/albums/e18/laurenceharrington/Mobile%20Uploads/IMG_20161218_071927_zpsdhoy7thq.jpg

http://i36.photobucket.com/albums/e18/laurenceharrington/Mobile%20Uploads/IMG_20161218_071925_zps6akjp3os.jpg

[michael everson]

I wonder if the slave wasn't all the way in when you measured and cut the rod. It should have more then enough travel for your setup.
Cant explain your stiffness. Are you using the Wilwood pedals? If so make sure nothings binding in the pedal box.
Mike

[lahrs37]

I wonder if the slave wasn't all the way in when you measured and cut the rod. It should have more then enough travel for your setup.
Cant explain your stiffness. Are you using the Wilwood pedals? If so make sure nothings binding in the pedal box.
Mike

I am using the Wilwood pedalbox - nothing appears to be binding. So it sounds like I went the wrong way - instead of trying to shorten the pushrod, I should try to make it longer?

[boat737]

Check out EdwardB's build threads. ( http://thefactoryfiveforum.com/showthread.php?8296-Mk4-7750-Build-Progress-Update/page2 starting at post #62, and http://thefactoryfiveforum.com/showthread.php?18591-EdwardBs-Mk4-8674-20th-Anniversary-Build/page8 post #291 and/to #307. His build threads, and his cars, are impeccable.) He went to a smaller, 1 inch master, as did I on his recommendation. That shortens up the slave travel just enough to pretty much prevent the slave piston from popping all the way out. Mine just starts to protrude about 1/8 inch or so. Pedal force is reduced as well. As for mine, haven't driven it yet (nor even started it), but testing it before engine install and after the engine install seems to provide the necessary fork travel. It all measures and looks to be just right.

If you do need to lengthen the slave push rod, just get a bolt about the right length and saw/grind the head off.

[phileas_fogg]

I had the exact same problem, described here: http://www.ffcars.com/forums/17-factory-five-roadsters/585658-hydraulic-clutch-question.html. After about a week and countless workings of the clutch, the problem mysteriously went away. My guess is that I had an air bubble in the system that eventually worked its way out. Also, I've never heard of anyone having to lengthen the slave pushrod.

Which is a long way of saying, work the clutch a bunch & re-bleed before you make any changes.


John

[rich grsc]

The throwout bearing must touch the pressure plate fingers, no free play.

[lahrs37]

I had the exact same problem, described here: http://www.ffcars.com/forums/17-factory-five-roadsters/585658-hydraulic-clutch-question.html. After about a week and countless workings of the clutch, the problem mysteriously went away. My guess is that I had an air bubble in the system that eventually worked its way out. Also, I've never heard of anyone having to lengthen the slave pushrod.

Which is a long way of saying, work the clutch a bunch & re-bleed before you make any changes.


John

I will definitely try this first.

[lahrs37]

Check out EdwardB's build threads. ( http://thefactoryfiveforum.com/showthread.php?8296-Mk4-7750-Build-Progress-Update/page2 starting at post #62, and http://thefactoryfiveforum.com/showthread.php?18591-EdwardBs-Mk4-8674-20th-Anniversary-Build/page8 post #291 and/to #307. His build threads, and his cars, are impeccable.) He went to a smaller, 1 inch master, as did I on his recommendation. That shortens up the slave travel just enough to pretty much prevent the slave piston from popping all the way out. Mine just starts to protrude about 1/8 inch or so. Pedal force is reduced as well. As for mine, haven't driven it yet (nor even started it), but testing it before engine install and after the engine install seems to provide the necessary fork travel. It all measures and looks to be just right.

If you do need to lengthen the slave push rod, just get a bolt about the right length and saw/grind the head off.

Gosh, his posts are so good. OK, that sounds like a good plan B.

[lahrs37]

The throwout bearing must touch the pressure plate fingers, no free play.

No free play when the clutch pedal is not depressed?

[michael everson]

Yes. Clutch fork should be against the throwout bearing.
Mike

[phileas_fogg]

Have you tightened the jam nut on the slave pushrod up against the rod end? I don't know if this is germane to your problem or not, but the information may help me solve a related hydraulic clutch problem.

Thanks,


John

[lahrs37]

Have you tightened the jam nut on the slave pushrod up against the rod end? I don't know if this is germane to your problem or not, but the information may help me solve a related hydraulic clutch problem.

Thanks,


John

I did tighten it. What is going on with your clutch system?

[boat737]

No free play when the clutch pedal is not depressed?

I may be missing something here, but when the clutch is fully engaged and the clutch pedal is not depressed, there should be play at the slave/fork arm. I have about 3/16". This will gradually decrease as the clutch disk wears, and the pressure plate fingers move out fractionally, which moves the clutch fork rearward (on the pivot ball style fork arm.) If there were no play, the fork would start to add pressure to the TOB and pressure plate fingers, and start to disengage the clutch. At which point the clutch would start to slip. There have been a couple posts on this subject, one fairly recently, but can't find it.

[rich grsc]

I may be missing something here, but when the clutch is fully engaged and the clutch pedal is not depressed, there should be play at the slave/fork arm. I have about 3/16". This will gradually decrease as the clutch disk wears, and the pressure plate fingers move out fractionally, which moves the clutch fork rearward (on the pivot ball style fork arm.) If there were no play, the fork would start to add pressure to the TOB and pressure plate fingers, and start to disengage the clutch. At which point the clutch would start to slip. There have been a couple posts on this subject, one fairly recently, but can't find it.
Sorry thats incorrect, throwout bearing should just ride the clutch fingers, with no pressure. And yes it will need to be adjusted once an awhile.

[boat737]

Sorry thats incorrect, throwout bearing should just ride the clutch fingers, with no pressure. And yes it will need to be adjusted once an awhile.

This from EdwardB's build thread, http://thefactoryfiveforum.com/showthread.php?8296-Mk4-7750-Build-Progress-Update/page2 post 62. I did mine the same. Again, maybe I'm missing something.

Here are pictures of the final setup, and a quick video I shot of the setup working. I shook the thing a bit to show the free play when the clutch pedal is all the way out. The included instructions say 1/8 inch. Multiple posts say 1/4 inch. It’s somewhere in that ballpark here for the mockup. I’ll get it all finalized when it’s for real. I’ll also put a tie wrap around the bellows on the slave cylinder so it’s not sliding around.

http://i867.photobucket.com/albums/ab234/edwardb123/Factory%20Five%20Mark%204%20Roadster%20Build/Engine/MVI_0114_zpsec012ef2.mp4
Click to play video.

[edwardb]

This from EdwardB's build thread, http://thefactoryfiveforum.com/showthread.php?8296-Mk4-7750-Build-Progress-Update/page2 post 62. I did mine the same. Again, maybe I'm missing something.

Here are pictures of the final setup, and a quick video I shot of the setup working. I shook the thing a bit to show the free play when the clutch pedal is all the way out. The included instructions say 1/8 inch. Multiple posts say 1/4 inch. It’s somewhere in that ballpark here for the mockup. I’ll get it all finalized when it’s for real. I’ll also put a tie wrap around the bellows on the slave cylinder so it’s not sliding around.

http://i867.photobucket.com/albums/ab234/edwardb123/Factory%20Five%20Mark%204%20Roadster%20Build/Engine/MVI_0114_zpsec012ef2.mp4
Click to play video.

For a cable drive clutch, agreed it should be adjusted with the TOB touching the clutch fingers. For the Mike Forte hydraulic clutch setup, I've followed Mike's instructions to leave a little slack in the system when it's a rest. Has worked fine that way. Either approach requires adjustment as the clutch wears.

[d_gatorfan]

You need to have a little slack. I had my slave about as short as I could get it and at about 10k miles I had to move the slave back. After breaking in the the clutch was not releasing fully. If I can get a picture I'll post to show what I did. Not sure why/how your slave is over traveling with Mikes stock size master and slave. My pedal hits the firewall before that happens.

[edwardb]

Hey all,

So I have been having issues with the hydraulic clutch setup from Forte. I have T-5 transmission with a stock clutch and the pedal was ridiculously stiff. Thinking that maybe I made the pushrod too short, I went to remove it and discovered that the slave boot was full of fluid. It turns out that the slave cylinder is overextending past the seal. You can see this in the pictures. I contacted Mike, but I was curious as to whether there is a simple fix to this?

Something is really wrong there. If the slave piston is all the way in there's no way the standard master cylinder is going to be able to push it out that far. Mike might be right that the slave wasn't in all the way. Maybe it's defective and not retracting all the way back in and that's also why it's so stiff? All pure guesses... The pushrod Mike Forte provides is way longer than needed. Usually an inch or more needs to be cut off. I've never heard of someone needing a longer one. You do have the little metal fitting he provides slid onto the end of the pushrod? That fits into the cup in the slave cylinder?

[CraigS]

Some info on hydraulic clutch systems. Just like a hydraulic brake system there is no freeplay other than that tiny 1/32 inch in the pedal pushrod to assure that the MC can return fully so the fluid can: 1-fill the MC from the reservoir or, 2- return to the reservoir if needed. In a cable or rod system (Yes there used to be rod systems, I am old) as the clutch wears you will lose freeplay so those systems need a manual adjustment. In a hydraulic system, remember above I said fluid needs to be able to return to the reservoir? That is your automatic adjustment for clutch wear.

[phileas_fogg]

I did tighten it. What is going on with your clutch system?

Same as you; the slave cylinder was extending too far. But over time it's "settling" - not extending as far as it did initially. I think the settling was caused by an air bubble, but I don't understand how a bubble got into the system since I filled it from the slave bleeder. This technique should have pushed all the air upwards - in the direction it wants to go - and out the reservoir. Now I'm watching the clutch carefully to make sure the settling has stopped.

[lahrs37]

Something is really wrong there. If the slave piston is all the way in there's no way the standard master cylinder is going to be able to push it out that far. Mike might be right that the slave wasn't in all the way. Maybe it's defective and not retracting all the way back in and that's also why it's so stiff? All pure guesses... The pushrod Mike Forte provides is way longer than needed. Usually an inch or more needs to be cut off. I've never heard of someone needing a longer one. You do have the little metal fitting he provides slid onto the end of the pushrod? That fits into the cup in the slave cylinder?

I did trim the pushrod down. In fact I went back and trimmed it even more thinking that might be the culprit. I am using the cup provided. Before the second trimming of the pushrod I noticed that it was not automatically fully retracting. I had to reach down and manually retract it with my hand. After I did that, the pedal would feel decent for the first push. After that the pushrod would again not fully retract and the pedal would feel very hard. When I went to trim the pushrod again is when I discovered it had been leaking. At the time I didn't think to check whether the slave was extending beyond the seal, though I suspect it was. After trimming and reinstalling is when I took the pictures that appear at the top of this post.

[michael everson]

You might need to start over. Here is what I would do. Disconnect the clutch line from the slave or at least open the bleeder. Push the cylinder all the way in by hand or appropriate tool. Attach a new longer push rod to the clutch fork with the threaded end into the rod end as far as it will go. Now slide the slave over it and hold it near the mounting holes. Make sure you are putting enough pressure on it to push the throwout bearing against the clutch plate. Measure the distance from the mounting holes to the holes in the slave. This is how much is needed to be removed from the adjuster. You now have the correct length. You should be able to bolt it up and take out any slack with the adjuster. bleed the system and your done. If this does not work, something else is wrong.
Mike

[lahrs37]

You might need to start over. Here is what I would do. Disconnect the clutch line from the slave or at least open the bleeder. Push the cylinder all the way in by hand or appropriate tool. Attach a new longer push rod to the clutch fork with the threaded end into the rod end as far as it will go. Now slide the slave over it and hold it near the mounting holes. Make sure you are putting enough pressure on it to push the throwout bearing against the clutch plate. Measure the distance from the mounting holes to the holes in the slave. This is how much is needed to be removed from the adjuster. You now have the correct length. You should be able to bolt it up and take out any slack with the adjuster. bleed the system and your done. If this does not work, something else is wrong.
Mike

That sounds like a good strategy.

[edwardb]

That sounds like a good strategy.

Just to add to the excellent advice from Mike, there is significant force from the clutch back through the TOB and the clutch arm. Try pushing the clutch arm manually to release the clutch. Good luck... When hydraulic pressure is released from the slave cylinder, there should be no issue with the clutch arm pushing the slave piston back where it belongs. If it's not doing that, either something is wrong with the slave or your clutch isn't working properly for some reason.

[lahrs37]

OK, so I followed Michael Everson's advice to a T. I got a new pushrod from the hardware store. I measured that amount that needed to be cut off - multiple times. I made my cut and installed it. I bled the system and immediately I could tell that it was the right length.
BUT...
The pedal still felt a bit heavy to me - almost the way the manual brake pedal feels. I thought maybe I just needed to depress the pedal a bunch of times and maybe some air I missed would be forced up to the reservoir. Instead what happened is that after a few rapid pedal depressions I began to see the first seal in the slave again. Curious, I went a few more time and the hole thing popped out and got wedged between the slave body and the fork. When I finally got the bolts that held the slave onto the transmission off, the clutch fork slammed back into place and shot the inner body of the slave cylinder like a bullet across the garage. It gave me a bit of a scare as I didn't realize how much pressure was still there (edwardb tried to warn me lol).
So whatever is happening, there is enough pressure that it moves the clutch fork without issues. The clutch fork still has an enormous amount of pressure on it, so I tend to think it is something in the hydraulic system.

[Norm B]

Your master cylinder must not be returning all the way. The fluid should be able to freely flow back to the reservoir when the clutch pedal is up.

[michael everson]

I almost think there is such a bad kink in the braided line that it wont let fluid back but you can over come it with your foot pressure. Remove the line from bot ends and inspect it. Also see if you can blow through it both directions.
Mike

[lahrs37]

Your master cylinder must not be returning all the way. The fluid should be able to freely flow back to the reservoir when the clutch pedal is up.

This is an interesting idea. After pumping the pedal a bunch of times I did hear a gurgling coming from the master cylinder....

[lahrs37]

I almost think there is such a bad kink in the braided line that it wont let fluid back but you can over come it with your foot pressure. Remove the line from bot ends and inspect it. Also see if you can blow through it both directions.
Mike


I will do this today.

[lahrs37]

Ok, so I took the system apart and blew in the braided line. There didn't appear to be any kink. I called Mike and showed pictures. He told me that by rapidly depressing the pedal I could suck in another "gulp" and cause the slave piston to extend too far. As far as the pedal feel, it seems like I might just not be used to American V8 clutches coming from Japanese cars. I am following edwardb's advice and ordered a 1" master cylinder to try and reduce the effort. As a bonus if there is a problem with the master that will take care of it. On a total side note, by bleeding the clutch so many times I accidentally stripped the bleeder screw. :( I can still do it by hand, but good grief! lol

[lahrs37]

So after installing the 1" master cylinder, the effort is reduced enough to be considered tolerable. I had to cut the pushrod of the new master to get my pedal height right. After doing that, I noticed the pedal now contacts the 3/4 tube like everyone warned - so I must be on the right track!

My Last question is: what has everyone done to cover the hole in the bellhousing that the fork comes out from? I can't imagine that it is a good idea to leave that uncovered. Thanks for all of the help!

[michael everson]

The open hole is not an issue.
Mike

[lahrs37]

The open hole is not an issue.
Mike

Good to know, thanks!

One more question, does anyone know a part number for the bleeder valve on the CNC slave cylinder? I bled it so many times I stripped it. :rolleyes: