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Hydraulic clutch issues......WTF

Discussion in 'The Hokey Ass Message Board' started by boutlaw, Nov 1, 2011.

  1. boutlaw
    Joined: Apr 30, 2010
    Posts: 1,239

    boutlaw
    Member

    I need some help with my hydraulic clutch setup. Its just not releasing the clutch. First off, I have searched and read most of the threads on the subject. Very educational, but none seem to address my partiucular issue.
    Here's the setup, 390 FE adapted to T-5. I am using the ECI swinging pedal assy, which has a 7/8" clutch master cylinder. The slave cylinder is the Speedway "puller" unit with 7/8 bore. I had to shorten the clutch arm about 3 inches to clear the floor structure. I built a bracket to mount the slave cylinder and it is pulling straight. I have bled the system and played with pedal travel by adjusting the m/c rod to lengthen and shorten in an attempt to gain more travel at the slave cylinder. The m/c cylinder stroke is only about 1/2 inch, that's all I can get, which only moves the slave about the same amount. The clutch is pretty damn hard to depress to get the 1/2 inch of travel. I started wiith some free play between the T/O bearing and the pressure plate, but since I was not getting any travel, I seated the TO bearing fully against the 3 pressure plate arms (not diaphragm type), but I am still not getting enough throw to release the clutch.
    First question...since the slave is a "puller", and the fluid is coming into the slave cylinder on the rod side of the internal piston (to pull on the clutch arm), it seems to me that the volume of fluid being forced into the slave is LESS than the amount moved by the m/c (of same bore) because there is less space in the slave bore due to the rod length/diameter that occupys the same space inside the cylinder. If that assumption is true, can't I get a larger slave so that the volume of fluid would be increased thereby increasing the stroke? Is that a correct assumtion? However, the dang pedal is so hard to push now, I don't need to increase the strength needed to depress the clutch.
    If I unhook the pull arm of the slave cylinder from its mount and press the clutch, the clutch pedal moves further (stroke) and so does the slave, probably 1 inch or so, so when testing the system with the slave unhooked, it appears the components would work. WTF am I missing here? Any and all comments/suggestions appreciated. Going now to take pics and post of slave and clutch arm and clutch m/c.
     
  2. boutlaw
    Joined: Apr 30, 2010
    Posts: 1,239

    boutlaw
    Member

    [​IMG]
     
    Last edited: Mar 12, 2018
  3. boutlaw
    Joined: Apr 30, 2010
    Posts: 1,239

    boutlaw
    Member

    [​IMG]
     
    Last edited: Mar 12, 2018
  4. boutlaw
    Joined: Apr 30, 2010
    Posts: 1,239

    boutlaw
    Member

    [​IMG]
     
    Last edited: Mar 12, 2018

  5. boutlaw
    Joined: Apr 30, 2010
    Posts: 1,239

    boutlaw
    Member

    I agree that more leverage would be needed with the shorter , but assumed the hyd setup could overcome the increased effort required. Seems I have read of people shortening their clutch arms for the same reason, clearance issues. Definitely something to consider.
     
  6. 48 Chubby
    Joined: Apr 29, 2008
    Posts: 1,014

    48 Chubby
    Member Emeritus

    First question-As the fluid is not compressable what ever comes out of the master cylinder goes into the slave cylinder, less only what is displaced by line expansion. Your reasoning is actually reversed. Greater volume at the slave cylinder will decrease pedal effort, but reduce slave cylinder travel.

    Second question-If the cylinder travel increases when disconnected from the mechanical assembly, then the mechanical assembly is restricting travel. Probably bottoming out.

    It seems to me that you have issues with leverage ratios and the restrictions created by shortening the throw out arm.
     
  7. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,476

    dreracecar
    Member
    from so-cal

    Is the clutch assy "NEW" or one that had been installed and functioning well up to that point? Had an issue once with a resto Cacklecar. Owner brought in a clutch that was "all set up,ready to go" installed it and it too was very hard to push the peddle and would not dis-engage. What I found out that the builder really did not set it up and the clutch arm fingers were not high enough meaning that when I bolted the cover on it compressed the ring too much and the arms went past center leaving not enough movment. Wound up shimming the hat up from the pressure plate (very common) untill the arms were in proper possistion put it back together and now I could opperate the peddle by hand and the clutch functioned normaly.
     
  8. boutlaw
    Joined: Apr 30, 2010
    Posts: 1,239

    boutlaw
    Member

    Thanks for the clarification Chubby, I had concerns about shortening the clutch arm, but feel sure that has been done before, maybe not that much though. I am going to the shop and prybar the damn thing to see if I can overcome the mechanical issues or at least see if I can move it a bit more. Can I increase m/c and slave cyl size to produce more force? Thanks again.
     
  9. ojai/jan
    Joined: Feb 6, 2008
    Posts: 110

    ojai/jan
    Member
    from ojai, CA

    Hi, I had a similar situation with my 1952 Plymouth with 392 hemi. Found that I did not have enough pedal travel. Made a notch in the floor to allow the pedal to move farther and now no problem.

    Jan in Ojai, CA
     
  10. Ole don
    Joined: Dec 16, 2005
    Posts: 2,915

    Ole don
    Member

    First to check is the alignment of the pushrod going into the clutch matser cylinder. The picture shows it to be off just a little. Then, the spacer washers appear to be to big. You could be binding the pushrod. Then, what D-Russ says. Three inches of a lever is a HUGE amount of change.
     
  11. AGREED! I stopped reading the original post soon as I got to the part where you wacked off 3" from the clutch fork to see the other responses. 3" is HUGE
     
  12. boutlaw
    Joined: Apr 30, 2010
    Posts: 1,239

    boutlaw
    Member

    dreracecar....thanks for the observation. The clutch and pressure plate are new/stock 390 truck components, FE 250 I think, so they were not in service beforehand. I recall pushing down on the "arms" with my foot and they seemed rather stiff but not overly so. I actually had 2 of the PP's and one had an arm that was a bit lower than the other two, even though it was new, so I selected the other one to install. I am sure the disc is installed properly, although I don't think you can install an FE clutch disc backwards anyway, as it hits the flywheel bolts. I am going to try a prybar and see if it moves more than the arm is allowing.
    Thanks for the information.
     
  13. monkeywrenching
    Joined: Feb 14, 2007
    Posts: 299

    monkeywrenching
    Member
    from maryland

    I would call Willwood to check specs but I think you have two issues. No leverage and not enough operating pressure.
     
  14. boutlaw
    Joined: Apr 30, 2010
    Posts: 1,239

    boutlaw
    Member

    Thanks jan for your comment. However, I am getting plenty of pedal travel, although I am unable to use it because of the minimal movement at the slave.

    ole don....the spacer washers are just 3/8 washers to center the pushrod and not the final installation. It does appear in the pic to be off a bit, but actually it is not, and the clevis bolt can spin so the linkage is not binding at that joint. Removing the 3 inchs in length for sure increased the force required to disengage the clutch, but the lack of room led to that decision, of course that doesn't make it right, but I figured I could overcome the increased force hydraulically. I sure thought I had seen others shorten their clutch arm on the HAMB, but maybe not that much. Thanks for the help. That could indeed be the whole problem. Can I increase cylinder sizes to increase the amount of force generated? Thanks again
     
  15. boutlaw
    Joined: Apr 30, 2010
    Posts: 1,239

    boutlaw
    Member

    Thanks Groucho and monkeywrenching....seems the general consensus is no leverage, and I certainly had concerns about that.
    I do need to fix it however and extending the clutch arm is not an option. I may have to go the hydraulic throwout bearing route, but have heard so much bad ju ju about leaking new units, that I elected to go this route. I still need to go prybar the thing to see if I may have other issues, but I don;t think so, I agree it boils down to leverage, but, hydraulics can move mountains, right, so can't I combine other components to overcome the shortened clutch arm? Thanks again for all your comments.
     
  16. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,476

    dreracecar
    Member
    from so-cal

    Clutch fingers shoud be angled out slighty and not flat or inverted. I dont think it is a leverage issue reason being that even if you push very hard that the clutch should still disengage. What you lose by shortening the arm is sensativity because if the pivot is the same the travel distance at the point of push/pull is shorter. You can also increase pressure by going to -3 line instead of -4
     
  17. a bigger master to a smaller slave will put more fluid into it
     
  18. JohnEvans
    Joined: Apr 13, 2008
    Posts: 4,883

    JohnEvans
    Member
    from Phoenix AZ

     
  19. F&J
    Joined: Apr 5, 2007
    Posts: 13,222

    F&J
    Member

    I don't understand why there is only 1/2" travel at the master without hooking it up to the slave.

    I do agree that 3" arm cut is going to be tough to work around, but the 1/2" travel at the master seems very wrong. The pic does not show why it can't travel further.
     
  20. 53sled
    Joined: Jul 5, 2005
    Posts: 5,817

    53sled
    Member
    from KCMO

    Factory hydraulic throwouts work for 100,000 miles, more expensive aftermarket units leak out of the box. See where this is going?
     
  21. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,476

    dreracecar
    Member
    from so-cal

    Braided -4 swells more when pressure is applied to a point where travel is increased before equal force is applied, now install hard line and a short isolater lenth of braided, then there is no difference
     
  22. I understand the concerns about leverage. But when you say you only have 1/2" of slave cylinder travel with it connected to the arm, and you get more travel with it disconnected, that makes me think you have some type of mechanical problem. You said you were going to try to pry the arm back with a prybar, I think this is a good idea. lets see how far that arm can travel and if that will release the clutch.
     
  23. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,476

    dreracecar
    Member
    from so-cal

    Going back over your post, why did you decide to go with a 7/8 master when both CNC and Wilwood reccomend 5/8 & 3/4? If they felt there would be a volume issue with the slave they would have said to use the 7/8.
     
  24. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,957

    gas pumper
    Member

    The motion ratio of the clutch fork arm is about 6:4. You taking 3 inches off that is gonna make it something like 1:1. Whatever. You need to measure this exactly. Than you can adjust your pedal linkage and bellcrank ratios to get the same travel that's needed.

    Factory setups have a 7:1 ratio or a 6:1 ratio at the pedal to master.

    Speedway has two of them purple slaves. One strokes 1 inch and the other 1 1/4, I think.

    You should have 6 to 7 inches of pedal travel. On a normal system this would give one inch of master travel. Than one inch of slave travel, than 1 divided by 6:4 is the throwout bearing travel. About 5/8 of an inch at the bearing.

    THIS is the number you need to hit. 5/8 at the bearing.


    Adjust the pedal ratio to get this number. and the 7 inch pedal travel results in 5/8 bearing movement.


    Frank
     
  25. check out pirate 4x4.com site lots of info there.
     
  26. boutlaw
    Joined: Apr 30, 2010
    Posts: 1,239

    boutlaw
    Member

    Thanks for all the comments....I ordered the ECI dual swinging pedal unit, clutch and brake mc's, and it came with the 7/8 bore clutch mc. Based on that, I purchased a 7/8" slave. I assumed the clutch MC provided by ECI would be adequate and had no reason to question their design. They certainly know more about it than I do. And, after reading posts on the HAMB, decided to match that size with the slave. BTW, I never mentioned it, but I am running a -3 steel braided line from the master to the slave, no hard line. I also assumed at the time that even though I shortened the clutch arm, that I would not need as much movement required by the longer arm, as mentioned by dreracecar.
    UPDATE...I can pry the clutch arm nearly all the way back to the opening in the bellhousing, but have no way to check if the clutch is alcually releasing, as I am by myself, but I have to assume it is, when prying on it. With the engine running, if I try to put the trans in gear, with clutch depressed, the car begines moving forward, so the clutch is almost disengaged with the slight movement currently generated, so I'm almost there, I just need a bit more.
    John Evans...I have not checked the pedal ratio. I'll have to research how thats is figured again. I believe the distance from the clutch pedal pivot to the top of the clutch arm where the MC clevis attaches is about 3 inches, but I will measure. I think I need that number and the pedal length from the pivot down. I will get those measurements.
    F&J...thanks for the comment....I am puzzeled by the 1/2 inch of movement as well and thought that was an improtant part of my description. I have NOT checked the mc rod movement with the slave disconnected as you suggested, only the slave movement, which is about double when disconnected. Let me go get some more data and repost.
    Thanks again for all the assistance guys.
    BTW....oledon...you were RIGHT, my clutch mc shaft was NOT exactly straight. I looked at it again and it was indeed a bit off. I added 2 more washers, one thin one by the heim joint and another flat...to get it straight. Thanks
     
  27. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,957

    gas pumper
    Member

    That -3 line, is it wrapped Teflon or rubber inside? You should use a teflon line, same as you would on a high buck brake system.

    BTW, I run a 7/8 master and 7/8 purple speedway pull slave on the T<<<<<
    Works great, no issues.
     
  28. boutlaw
    Joined: Apr 30, 2010
    Posts: 1,239

    boutlaw
    Member

    gas pumper...thanks for the insights. I should be getting close to the 5/8 inch now, at the TO bearing. I will have to measure that to be sure.

    UPDATE...I took some measurements so the pedal ratio could be determined.

    clutch arm pivot point to CL of clevis bolt hole = 3 inches
    clutch arm pivot point to CL of pedal pad = 14.5 inches

    clutch MC rod movement with slave not bolted to bracket and clutch arm = 1 1/4 " ***
    slave rod movement with slave not bolted to bracket and clutch arm = 1 1/4 "
    clutch MC rod movement with slave bolted in place = 1/2 - 3/4 "

    pedal movement (up to down) without being attached to clutch MC = 9.5 "
    pedal movement (up to down) attached to clutch MC = 3.5 " ***

    It seems that the MC/SC movements are the same, i.e 1 1/4 inch when the slave is not attached, but as soon as the slave is attached the slave movements drops to about half, i.e 3/4 inch.

    ***Another item I should mention....with the slave not bolted in place, the clutch pedal will move the MC rod 1 1/4 inch into the MC, and the slave the same amount. HOWEVER, if I press the clutch one more time, the MC rod movement will only be 3/4 inch.
    Unless I pull out on the SC rod manually after getting the 1 1/4 " movement mentioned in the previous sentence, the slave will only move 3/4 inch on that second push. I did put a spring on the clutch arm to try and pull it back but apparently it needs to be a stronger spring. Regardless, when everything is hooked up, I'm only getting about 3.5 inches of pedal movement (up to down)and 3/4 inch at the SC.

    Can someone chime in and assist with the pedal ratios. I could not find the post I had seen previously regarding determining pedal ratio.

    The -3 SS brake line is teflon coated.
     
  29. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,957

    gas pumper
    Member

    14.5 ./. 3=4.83
    this is the pedal ratio.

    6 will give a harder pedal than 7. Shoot for 7. 14.5 ./. 2.1= 6.90

    Move the 3 inch hole to 2.1. drill a new hole. give it a try.
     
  30. boutlaw
    Joined: Apr 30, 2010
    Posts: 1,239

    boutlaw
    Member

    I don't see any way to move the clutch MC rod hole down to 2.1. If I do that, the angle of the rod entering the MC would be severe. Isn't 6 or 7 to 1 considered the basic or common pedal ratio? If so, why would ECI, or any manufacturer, go with a ratio that is less desirable? I DO appreciate your input, because I am obviously not that knowledgeable about this subject, but I just can't see any way to shorten the pivot point and maintain a straight shot on the clutch MC rod.
     

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