Another clutch hydraulics thread
06-11-2008 | 02:02 PM
#16
Rennlist Member
Joined: Feb 2003
Posts: 29,956
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From: saratoga, ca
his easy pedal to depress , might indicate too much spring pressure pushing down and maybe blocking the return fluid port
Mk
Mk
Verify the clutch preload proceedure. I had simular problems with the cluch going bad after ~30 minutes or after a long drive w/no shifting. I adjusted the preload and the problem was fixed.
Scott with username hupp did the following writeup recently.
I agree with some of the others -- sounds like you have a air in the system. Avoid letting crazy creative solutions creep into your head at this point because these systems are quite simple and it's usually a simple thing causing problems.
Take a deep breath the start from step one (assuming you have the oem parts in the car).
--Remove the pedal rod at the clutch pedal.
--Bleed the clutch again.
--Remove slave from the bell with lines attached and with bleeder closed, slowly push the slave rod in until it reaches its stop. Slowly release -- then repeat this multiple times. This is done to force the last remaining air pocket in the master back to the reservoir. AND turst me, this air pocket will be there no matter how long you bleed.
--Install slave.
--Install pedal rod with correct pre-load or lack of pre-load (as mark mentioned 1mm gap) depending MY. The rod length can be adjusted by loosening the lock nut and then turnung the rod in the appropriate direction to lengthen or shorten. This is an important step and what you described previously as the clutch getting worse after 30 min sounds as if this rod adjustment is not correct. Too much pre-load causes the master piston to sit too far forward. This blocks the ports that allow the clutch/brake fluid to flow freely as the clutch is used and you essentially pump more air in with each use.
On the mechanical side of things:..........
__________________
Scott
1979 928 5-Speed, LSD
Kiln Red
Scott with username hupp did the following writeup recently.
I agree with some of the others -- sounds like you have a air in the system. Avoid letting crazy creative solutions creep into your head at this point because these systems are quite simple and it's usually a simple thing causing problems.
Take a deep breath the start from step one (assuming you have the oem parts in the car).
--Remove the pedal rod at the clutch pedal.
--Bleed the clutch again.
--Remove slave from the bell with lines attached and with bleeder closed, slowly push the slave rod in until it reaches its stop. Slowly release -- then repeat this multiple times. This is done to force the last remaining air pocket in the master back to the reservoir. AND turst me, this air pocket will be there no matter how long you bleed.
--Install slave.
--Install pedal rod with correct pre-load or lack of pre-load (as mark mentioned 1mm gap) depending MY. The rod length can be adjusted by loosening the lock nut and then turnung the rod in the appropriate direction to lengthen or shorten. This is an important step and what you described previously as the clutch getting worse after 30 min sounds as if this rod adjustment is not correct. Too much pre-load causes the master piston to sit too far forward. This blocks the ports that allow the clutch/brake fluid to flow freely as the clutch is used and you essentially pump more air in with each use.
On the mechanical side of things:..........
__________________
Scott
1979 928 5-Speed, LSD
Kiln Red
06-11-2008 | 02:06 PM
#17
Thread Starter
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Joined: Dec 2006
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From: Elmhurst, IL
Just to be perfectly clear, the pedal rod should be just short of actually touching the MC? Is that right? And I should also check for a 43mm gap in front of the spring?
Thanks guys.
Thanks guys.
06-11-2008 | 02:52 PM
#20
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Joined: Jan 2007
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From: Fremont, CA
It has been over a year since I dealt with this but the pedal rod should touch the master cylinder and then be pre-loaded 1mm. The clutch should disengage at full pedal extension and start engaging almost immediately when you start releasing. Don't confuse the feel of this clutch with the feel of a typical clutch that engages ~50% pedal travel.
06-11-2008 | 03:05 PM
#21
Thread Starter
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Joined: Dec 2006
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From: Elmhurst, IL
good point nosnow, i was using confusing terminology. then the term pre-loading means the rod should be just a little long and just pushing in on the mc a touch even when my foot is off the pedal. is that right?
thanks for dealing with these silly, uninformed questions.
thanks for dealing with these silly, uninformed questions.
06-11-2008 | 05:33 PM
#24
Drifting
Joined: Dec 2003
Posts: 2,902
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From: an unnatural suburban habitat
I just tried plunging the slave, and the pedal feel is firm now. I will see how that goes.
I was under the (false) idea that the push rod was to have 1 turn of preload pushing on the master. No preload now.
EDIT: works like it should, very nice. We will see if the sponginess comes back, but perfect now.
I was under the (false) idea that the push rod was to have 1 turn of preload pushing on the master. No preload now.
EDIT: works like it should, very nice. We will see if the sponginess comes back, but perfect now.
Last edited by Ispeed; 06-12-2008 at 12:13 AM.
06-11-2008 | 08:11 PM
#25
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Joined: Jan 2007
Posts: 862
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From: Fremont, CA
I double checked mine and there is a preload (pressure on the master). My car is an 82 w/double disk.... It works and I think that is what is said in the manual. But as I said I have not played with the adjustments for over a year.
06-12-2008 | 06:02 AM
#26
Drifting
Joined: Nov 2001
Posts: 2,233
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From: zürich, switzerland
HTML Code:
I was under the (false) idea that the push rod was to have 1 turn of preload pushing on the master
Later versions of the WSM "the push rod is to have 1 turn of preload pushing on the master"
No idea why or exactly when they changed or if the later advice is applicable to the early clutches.
On mine (81s) I tried both ways to see which gave the better feel; ended up with about 1/2 turn of preload
Marton
06-12-2008 | 09:26 AM
#27
Drifting
Joined: Dec 2004
Posts: 2,235
Likes: 2
From: Atlanta
Thanks Marton, I didn't think I was crazy. My version of the WSM definitely states to have a 1mm gap and I know it's an early version. No idea why they might have changed, but mine is adjusted with the gap and works perfectly...now.
06-12-2008 | 04:15 PM
#28
Burning Brakes
Joined: Mar 2008
Posts: 930
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From: At the foot of Pikes Peak
My service manual states the 1mm gap so I guess this is an older version.
I tried playing with it in different locations but kept coming back to that 1mm gap and that seemed to work best for me.
The place I kept getting air was in the master though so be sure to get that bled or you will run into problems after you use it for a bit, as you stated it was doing to you.
I'm still trying to wrap my head around what I ended up doing and looking at notes and pictures. It has been working good so far but now when I release the clutch I'm getting some noise that wasn't there before so I imagine I'll be going back in there this weekend so I'll try to keep you posted.
I bled the dang thing at least 9 times so it's always the last time that it ends up working
Ha ha ha
I tried playing with it in different locations but kept coming back to that 1mm gap and that seemed to work best for me.
The place I kept getting air was in the master though so be sure to get that bled or you will run into problems after you use it for a bit, as you stated it was doing to you.
I'm still trying to wrap my head around what I ended up doing and looking at notes and pictures. It has been working good so far but now when I release the clutch I'm getting some noise that wasn't there before so I imagine I'll be going back in there this weekend so I'll try to keep you posted.
I bled the dang thing at least 9 times so it's always the last time that it ends up working
Ha ha ha
06-12-2008 | 10:46 PM
#29
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Joined: Jan 2007
Posts: 862
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From: Fremont, CA
bleeding this clutch system is very difficult. I ended up putting the rear of the car higher than the front so that the fluid in the master resevouir was always at the front. I also kept it completely topped off and bled the extra fluid through the front caliper. I really dread having to flush the fluid which will be on my to do next year.