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Hydraulic clutch problems (bleeding?)

Discussion in 'The Garage' started by CyberSniper, Mar 28, 2005.

  1. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    So, I've got a hydraulic clutch now. After trying to bleed it for about an hour I still only barely get enough travel out of the slave cylinder to disengage the clutch when the pedal is pushed to the floor. I mean barely. The slave cylinder doesn't really start moving until the pedal has moved about 1.75".

    I've never had a 465 so this might be normal but in all the other hydro clutch applications I've had they start disengaging the clutch about 3/4" of pedal movement.

    Are there any tricks to it? Is there any adjustments to make anywhere?
     
  2. sled_dog

    sled_dog 1 ton status

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    remove the slave cylinder, angle it at a 45* angle so the bleeder is up at the top. Crack it, then try bleeding like this. Always works.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Is the master aftermarket? If it's like the one I originally bought, it may have a threaded section that you can lengthen/shorten, which affects pedal travel/clutch engagement/fork travel a LOT.

    If not, the way I bled mine was pretty simple. Pull the cap off the reservoir. Make sure it's not going to go dry. Crawl under truck. Remove slave from bell. Keep it at an angle so the bleeder is the highest point. Crack the bleeder. Force the rod in a ways, seal the bleeder, let the rod out. Repeat.

    I *think* if you leave the slave bolted to the bellhousing LOOSELY, you can probably use a large screwdriver between the clutch fork and slave cylinder rod to pry the rod back in, and that will still allow you to keep the bleeder "up".

    If this is an old master cylinder or slave, they MIGHT have failed with the bleeding process. But try bleeding as suggested (bleeder being highest point on slave is really important) and see if that works first. I see I'm not the first response, but I found my way was very easy by myself, and works.
     
  4. sled_dog

    sled_dog 1 ton status

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    it really just sounds to me like he needs to do the bleeding process I noted, and you did as well.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    I agree, just wanted to point out the adjustable master cylinder rod issue I ran into. Clutch was bled fine, but pedal travel was excessive, and I'm sure if I played with it enough, (before I broke the rod by leaving slave unbolted and letting neighbor step on clutch pedal) I could have had the pedal travel to the floor without disengaging the clutch fully.

    But stock this was not used, and my aftermarket replacement also did not use the adjustable rod, so it seems unlikely its the case here.
     
  6. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    Well, the entire clutch system is new except for the master cylinder, pedals, and bellhousing...

    The master cylinder looks like brand new. The only dirt on it was from handling.

    I'll give the "pull the slave cylinder off and bleed it dangling there" method a whirl. I asked my Dad if we should do that but we were just trying to get it on the trailer so I could get home. Didn't end up making it home until 1:15am after a nine and a half hour drive.

    So far I have:
    $115 into a clutch fork and line (from stealership)
    $160 for a 12" Perfection clutch set
    $67 into clocking ring
    $76 for a 1 piece brand new flywheel
    $72 for slave cylinder
    $86 into a short style 465/208 adapter
    $150 for the transmission and transfer case
    $5 for a clutch reservoir from TJ
    $40 for bellhousing/pedals/master cylinder
    = $771
    and that happens to be about 1/3 of what I have into the entire rig (tires included).

    [​IMG]
    [​IMG]
     
  7. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    when i bled mine, i did it like you normally do brakes. took forever to get fluid to the slave, then after getting all the air out, the pedal travel didn't feel right, had like 2" of nothing like yours. i drove it like 3 miles and the pedal got tighter, down to about 3/4 to 1". ive been driving on it ever since and have no problem what so ever with it. this was on factory 89 stuff also.

    i also bled mine mounted fully to the bellhousing, my truck was leaned back slightly.
     
  8. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    OK, so today I spent about an hour and a half and more than a pint of brake fluid later I have no better pedal. I tried both bleeding it on the trailer with the nose pointed up and with the slave cylinder dangling with the body at 45° with the bleeder at its highest point.

    I've always had good luck with gravity bleeding...

    I'm wondering if the rod that goes between the slave cylinder and the clutch fork is too short. I was contemplating getting a bolt and cutting it off then grinding similar points on it but half an inch longer than the one that's currently in there.

    What do you guys think?
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    If you've got the right bellhousing, slave cylinder and clutch fork, then messing with the rod is just a bandaid.

    I haven't had to play around with my setup much, any chance the throwout bearing/fork aren't setup right? I know the hydraulic fork is different, positive it's the right part #? (I've got the parts diagram online if you have the part number to check against)

    Another thing, do you have to compress the slave cylinder rod to install the slave? I just put mine back on the other day, and the rod needed compressed about 1/2 its length, which puts pressure on the fork.
     
  10. sweetk30

    sweetk30 professional hooker Premium Member

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    if you have a vac pump try sucking the fluid down threw the system. this works to.
     
  11. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    The fork I bought is GM 1559-2270
    The hydraulic clutch hose I bought is GM 1553-7760
    The slave cylinder I bought is Tru Torque (Advance Auto) CS37791
    The clutch kit I bought is a Perfection Hytest MU19091
    The flywheel I bought is a MotorMite 04623 (GM 1010-5832)

    I ordered them for a 1987 K20.




    Eh, I'm mostly certain that I got the right stuff. The bellhousing and pedals came from some year pickup like ours... I'm not sure what year. I just assumed that the bellhousing and master cylinder were the same over the 85-87 range.

    I do have to compress the slave cylinder about 1/3-1/2 of its stroke to put it in. It has to go about another inch before it starts depressing the clutch.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Dang...parts manual doesn't show the part number for the clutch fork. No idea whats up with that. (Here if you or anyone want to look at the pieces/part numbers)

    I was mentioning bellhousing just as a comment that if all the pieces are correct, that influence how the rod hits the fork, then there can't be an issue with the rod. Has to be a pressure issue at that point.

    Any chance you can "pump up" the pedal? I know when my brake master was failing I could get more pressure/less travel out of the pedal if I kept pumping it.

    With new parts, you certainly don't expect an issue with bad seals though.

    Somewhere in those part numbers you posted is the right throwout bearing for the hydraulic setup too? Don't have access to mech. clutch parts list, but I believe that changed as well.

    As installed, the rod IS putting slight pressure against the fork, right? (basically, no fork freeplay with the slave cylinder installed) On mine the fork is basically "tight" (from slave cylinder spring pressure) against the throwout bearing all the time.

    Just throwing stuff out there, I know people have a real tough time bleeding these setups on occasion, guess I've been lucky.
     
  13. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    Well, I got the bellhousing from GMCLegacy, and he pulled it out of a pickup like ours. So I just ordered everything for an 87K20 because I figured it'd get me the large clutch designed for hydro and all the right pieces. I went to the dealership to get the fork and hose just to make sure I got the right pieces.

    But, that rod for the slave cylinder could be for something else... since I bought the slave cylinder kit from a non-GM source so it might be a "universal" thing that they use on all different setups. I know on El Caminos they used weird clutch forks.

    The only thing not brand spanking new is the master cylinder... I suppose it could be bad but I doubt it. I'd expect it to leak or something if it was bad.

    Well, there is spring pressure from the slave cylinder holding the rod into the fork... but there's a lot of travel before the fork ever even starts pushing the throwout bearing into the fingers. I'd have to look when I get home but I'm pretty sure I can move the fork a good inch with my thumb before I start applying pressure to the clutch. This results in about 2" of pedal travel.

    At one time, I thought I could "pump up" the clutch and get more pedal but it seems that it's just my legs getting tired.
     
  14. mtrdrms

    mtrdrms 1/2 ton status

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    I was bleeding my clutch for days until I found out what was wrong. I was opening the bleeder too much. I was opening it like 1/4 to 1/2 turn and this was letting air in through the bottom of the bleeder valve itself. I found once I just cracked it and closed it right away it began to get pressure. Just my .02. Good luck.
     
  15. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    OK, I'll give that a whirl when I get home and see if I can find a neighbor to operate the pedal for me. I've been opening it about 1/4-1/3 turn. Anything less and the fluid doesn't come out by itself.
     
  16. mtrdrms

    mtrdrms 1/2 ton status

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    Is it just straight fluid coming out or are there some bubbles too? I was getting bubbles just about every cycle. I was sure there was air entering the system somewhere so I replaced the master, slave and line until I found out my procedure was off.
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    That sounds suspicious to me, but I haven't actually put pressure on the fork with my finger as assembled.

    I'm reasonably certain that with the fork being pushed by slave spring pressure, the fork/throwout should be right against the clutch, and impossible to move with your fingers.

    The throwout fits into the clutch fork, and the throwout rides right on the pressure plate fingers if any pressure is applied to the fork, so if the slave spring is putting any pressure on the fork (as it should), the throwout should be against the clutch fingers. The throwout clips into the fork, so there should be *no* play between the fork and throwout.

    Now I'm only dealing with my setup, and it's the only one I've ever had to play with, so it's possible my experiences are atypical. Maybe someone else will chime in with how theirs acts.

    With air in the lines or not, the rod in the slave will extend as far as possible because of the spring inside the cylinder.
     
  18. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    Right click, save as to watch the slave cylinder move

    There definitely isn't any play between the throwout and the fork.

    There's a solid 1/2" probably as much as 3/4" of movement of the slave cylinder before the throwout contacts the fingers in the clutch. Since I have no boot on the bellhousing I can watch it move. Well, I shouldn't say "contacts" but I should say "resistance".
     
    Last edited: Mar 31, 2005
  19. dyeager535

    dyeager535 1 ton status Premium Member

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    Got a chance to crawl under my truck today. With my setup all bolted up and bled, there is NO play at the fork whatsoever. It is obvious the slave is pressing the fork/throwout against the pressure plate fingers even at rest. With all the finger pressure I could muster I couldn't move it.
     
  20. 85m1009

    85m1009 1/2 ton status

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    Just another opinion... I finally had to reverse bleed my hydraulic throwout bearing setup on the nv4500. We worked off and on for days trying to get the air out. Finally I used the mity vac and used the fitting that fits the inside bore of the master cylinder. Hooked up a hose to the bleeder and ran it into a full pint of fluid. I pulled most of the pint up through the system and it worked perfectly. Time spent 1 minute.
     

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