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Thread: Hydraulic throwout bearing problem :(
          
   
   

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  1. #1
    68Chevelle's Avatar
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    Hydraulic throwout bearing problem :(

     



    Hope this is a good place to post this (kind of a universal question) I have a hydraulic throwout bearing in my 27 Tudor and I got the thing bled. The problem is that the throwout bearing moves maybe a quarter of an inch and does not disengage the clutch. My Dad and I put the shims in per the intructions with pretty close tolerances... It is supposed to move roughly double the 1/4" it's moving.

    The setup I'm using is a remote mounted wilwood 1" master cylinder. I built the car to have swing pedals so the master cylinders are in the cowl section up high and not under the floor (don't need residual valves for the brakes) The hydraulic throwout bearing is the $99 one from speedway motors. The master cylinder has a one inch stroke and does travel the whole 1" while depressing the pedal... It is an sbc engine with a saginaw 4 speed behind it with a stock clutch. I can get some pics posted if they may help in answering why the throwout bearing doesn't move more...

    Thanks for the help,

    Thomas
    Last edited by 68Chevelle; 12-30-2011 at 03:25 PM.
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  2. #2
    rspears's Avatar
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    It sounds to me like you've still got air in the system. That unit says that it works with a 3/4" Wilwood MC, and you're running a 1" which gives you a significant increase in volume flow. The Speedway unit moves 0.688" full stroke, well over 5/8". You're getting only 1/4" - you've got air.
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  3. #3
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    I run the very same system with no problems. I would also say air in the system.
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  4. #4
    Dave Severson is offline CHR Member/Contributor Visit my Photo Gallery
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    Yeah, I'd guess either air in the system, or you have the wrong throw out bearing.... sometimes they can be a real nasty to get bled!
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  5. #5
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    I agree with Dave,them can be boogers to bleed,even the factory setups.
    Sometimes if you are sure its bled and still no pedal, just leave it sit overnight with the reservoir cap off and it'll sometimes burp itself while ya sleep. A few I've had to inject fluid with a big hypodermic thru the slaves bleeder. Also make sure you have the rod from the master to the pedal adjusted all of the way out so you get the most stroke on the pedal. After you get it bled then adjust that rod to about 1 to 1.5 inch of free play.

  6. #6
    Dave Severson is offline CHR Member/Contributor Visit my Photo Gallery
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    Only place we ever had any degree of success with hydraulic throw out bearings was circle burnin' in late models... Tried them on the street and drag racing, decided they were too much grief and went back to using a master cylinder and slave cylinder or mechanical linkage......
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  7. #7
    68Chevelle's Avatar
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    Thank you all for the great info and advice. I will take the cap off and let it sit over night...

    There is fluid shooting out of the bleeder of the throwout bearing when we are bleeding it but it does feel like it isn't building much pressure.

    What would be a good way to fully bleed the thing? I don't have a vacuum type bleeder or anything made specifically for the job but have had success with a dried out water bottle with brake fluid in it and vaccum hose hooked to a slave cylinder. Would that be a good method, just hook it up to the throwout bearing? Or should I just run a hose from the throwout bearing to the reservoir and bleed it like I was bench bleeding an M.C. ? Or maybe I'm totally off base :/

    Once again thanks for the help, it is truly appreciated!
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  8. #8
    Dave Severson is offline CHR Member/Contributor Visit my Photo Gallery
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    No idea if it's the correct way or not, but I would start off with gravity bleeding the system first... I'd block the clutch pedal down on the floor with a broom handle between the steering wheel and the clutch pedal, then take the cap off the master cylinder, then crack the bleeder valve open on the TO bearing about 1/4 turn. Big thing is to make sure the master cylinder doesn't run out of fluid!!!! I'd keep an eye on the fluid level, and let the fluid seep out the bleeder and through the bleeder hose into a drain pain. The more problems I'd been having bleeding the system, the longer I would let it gravity bleed, but usually at least a few hours....
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  9. #9
    ojh
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    As another said, the MC is too big and when it is working right you'll have a hard time getting the right pressure, pedal will be too hard. Since the pedal isn't too hard and they are easier to bleed then what the comments suggest i am thinking you are too far away from the pressure plate.
    Having messed with a number of them i favor the slave cyl, you can see the whole hydraulic system in a single glance, i have a McLoed in my race car and it was a bear to get it shimmed right.
    Last edited by ojh; 12-31-2011 at 07:40 AM. Reason: clarify

  10. #10
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    Ojh is also correct but be careful to not shim it to much or it will burn the clutch out of it. Done that on mine also but caught it in time. It is great after you get it right tho.
    Sometime Kool is the Rule But Bad is Bad

  11. #11
    68Chevelle's Avatar
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    Well Dave, I did the gravity bleeding that you suggested and let the thing sit overnight. The fluid level didn't seem to go down at all. I temporarily mounted the reservoir up higher than the mc, took the cap off, tied the pedal fully down, and cracked the bleeder. The fluid probably should have seeped out right?

    Ojh, I will go measure on a spare saginaw and double check to make sure the system is shimmed right. I would think that even if it wasn't shimmed right that I should still be able to see the correct amount of movement or is this not true of these to bearings if they are shimmed incorrectly? Also with the limited amount of movement that I do get out of the TO it seems to be moving the pressure plate almost instantly...

    Sg4356, you said you have the same setup as I do even the 1" mc and it works fine? Was it real tough to bleed/ get to work properly? How much movement do you get out of the TO?

    Thanks for the help guys, this one is really getting me frustrated...
    Me: I don't know how to build a hot rod.
    Old Hot Rodder: You ever build a model car?
    Me:Yeah...
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  12. #12
    68Chevelle's Avatar
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    Well I got it figured out... Kind of by mistake really, I just pushed the pedal down real hard with one arm pushing at the bottom of the pedal and the other at the top pulling and it worked. After that the pedal moved smoothly and disengaged the clutch. Maybe the pressure plate was "stuck" to the disk and flywheel? The clutch hadn"t been disengaged in over 2 years. Guess the gravity bleeding did do the trick after all... Think I will switch to a 3/4 mc though, the pedal wasnt overlly hard to push in but it could benefit from being softer.

    Still can't drive the hot rod yet, it turns out there is a lip on the pressure plate that hits the AN hose of the TO when the clutch is fully diengaged. Could cause some damge real fast, the hose does have a gash in it now... At least I can see what is wrong with the car this time lol!

    Thanks again for the help and tips, I will put them to good use on any car I build!

    Thomas
    Me: I don't know how to build a hot rod.
    Old Hot Rodder: You ever build a model car?
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  13. #13
    Dave Severson is offline CHR Member/Contributor Visit my Photo Gallery
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    Good deal!!!! Always easier to fix something once you realize what the problem is!!!!
    Yesterday is history, tomorrow is a mystery, Live for Today!
    Carroll Shelby

    Learning must be difficult for those who already know it all!!!!

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