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Thread: A clutch question for bill R or winfred

  1. #1
    Join Date
    Jan 2004
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    West Palm Beach, South Florida
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    Default A clutch question for bill R or winfred

    Alright guys, sorry to call you out individually, but I'm gonna have a feeling you guys are going to offer me the best advice on this.

    I searched the archives, and there are a lot of posts about soft clutches/clutches that suddenly engage at the very bottom of the travel, but they're all a permanent thing. My problem is intermittant.

    Anyway, I get the usual symptoms of hydraulic pressure loss: pedal travels about 1/4 of the way before engaging, feels spongy, and doesn't snap back up as fast as usual. The clutch engages at the very, and I mean very, bottom of the travel, but I have no problem starting or shifting smoothly.

    Here's where it gets complicated- it happens after I've been driving on the highway for a long time, like more than 2 hours. For example, I noticed it when downshifting for a tollbooth, and then consequently upshifting while I'm leaving. Again, getting off the exit ramp, it feels all spongy. Now the REALLY strange part- it goes away after a little stop and go driving!! And when I say goes away, I mean like there is 0 travel between the time you step on the clutch and the time that you feel the return pressure of the clutch- its perfect.

    So, I guess my first question is: Is there any way that these can get air in the lines and then later get air out of the lines (not necessarily "self bleeding", but I suppose thats an option)?

    The clutch was replaced in the summer of 02 with a new pressure plate, to bearing, the usual clutch job. On top of that, they replaced the master clutch cylinder, because it had leaked, dumped out hydraulic oil on the clutch, and consequently glazed it. They also replaced the clutch slave cylinder "as preventative maintenance". Everything has been great until now.

    Whew, that was long. Sorry to make you guys read all that. Any thoughts? I wish I could get underneath the car and look for trans leaks, but its been raining all day and yesterday .
    93 525i / 01 330Ci / 98 Camry / 91 Volvo 240 / 99 Jeep GC

  2. #2
    Join Date
    Jan 2004
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    4,150

    Default My guess would be clutch master cylinder, simply due to the fact that at highway

    speeds you're not using the clutch much, so the air thats in the system accumulates and makes the pedal spongy and soft... after driving stop and go you're using it alot more , as in pumping the pedal up and down more so it pumps up firm, then if you didn't use the pedal for awhile you'd find it goes down further and is spongy... either a leak at the slave or master either one could cause it but i'm betting on master. Look up under the dash where the master is for fluid leakage...Its possible that air was not bled out of the system back when you had the clutch done but not likely, not if its been working fine up till recently.




    Quote Originally Posted by DanDombrowski
    Alright guys, sorry to call you out individually, but I'm gonna have a feeling you guys are going to offer me the best advice on this.

    I searched the archives, and there are a lot of posts about soft clutches/clutches that suddenly engage at the very bottom of the travel, but they're all a permanent thing. My problem is intermittant.

    Anyway, I get the usual symptoms of hydraulic pressure loss: pedal travels about 1/4 of the way before engaging, feels spongy, and doesn't snap back up as fast as usual. The clutch engages at the very, and I mean very, bottom of the travel, but I have no problem starting or shifting smoothly.

    Here's where it gets complicated- it happens after I've been driving on the highway for a long time, like more than 2 hours. For example, I noticed it when downshifting for a tollbooth, and then consequently upshifting while I'm leaving. Again, getting off the exit ramp, it feels all spongy. Now the REALLY strange part- it goes away after a little stop and go driving!! And when I say goes away, I mean like there is 0 travel between the time you step on the clutch and the time that you feel the return pressure of the clutch- its perfect.

    So, I guess my first question is: Is there any way that these can get air in the lines and then later get air out of the lines (not necessarily "self bleeding", but I suppose thats an option)?

    The clutch was replaced in the summer of 02 with a new pressure plate, to bearing, the usual clutch job. On top of that, they replaced the master clutch cylinder, because it had leaked, dumped out hydraulic oil on the clutch, and consequently glazed it. They also replaced the clutch slave cylinder "as preventative maintenance". Everything has been great until now.

    Whew, that was long. Sorry to make you guys read all that. Any thoughts? I wish I could get underneath the car and look for trans leaks, but its been raining all day and yesterday .

  3. #3
    Join Date
    Dec 2003
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    baton rouge, loserana
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    Default

    that about covers it

    Quote Originally Posted by Bill R.
    speeds you're not using the clutch much, so the air thats in the system accumulates and makes the pedal spongy and soft... after driving stop and go you're using it alot more , as in pumping the pedal up and down more so it pumps up firm, then if you didn't use the pedal for awhile you'd find it goes down further and is spongy... either a leak at the slave or master either one could cause it but i'm betting on master. Look up under the dash where the master is for fluid leakage...Its possible that air was not bled out of the system back when you had the clutch done but not likely, not if its been working fine up till recently.
    all america wants is cold beer warm cat and a place to take a poop with a door on it

  4. #4
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    Default

    Thanks for the reply bill, and thanks for the in-depth diagnosis.

    I assumed that air must be getting in the system somehow, the master clutch cylinder seems to be the likely culprit. But.....when I let the car sit overnight, its still firm in the morning. Would letting it sit overnight have any effect on relieving the pressure?

    What I'm saying is that I don't understand why it will have air in it/lose pressure on the highway, but when it sits overnight it doesnt?
    93 525i / 01 330Ci / 98 Camry / 91 Volvo 240 / 99 Jeep GC

  5. #5
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    Jan 2004
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    Default You got me... I would think that sitting overnight would do it also but

    maybe the agitation of driving and shaking the reservoir has something to do with it...? How high is the fluid level?







    Quote Originally Posted by DanDombrowski
    Thanks for the reply bill, and thanks for the in-depth diagnosis.

    I assumed that air must be getting in the system somehow, the master clutch cylinder seems to be the likely culprit. But.....when I let the car sit overnight, its still firm in the morning. Would letting it sit overnight have any effect on relieving the pressure?

    What I'm saying is that I don't understand why it will have air in it/lose pressure on the highway, but when it sits overnight it doesnt?

  6. #6
    Join Date
    Mar 2004
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    Default

    That it doesn't happen overnite is a very important distinction and likely rules out the MC. Check the flex hose and all connections between the master and slave cylinders for leaks. You may have a small leak that allows air to be forced into the system at highway speeds. I had the same problem on an MGB, clutch hydraulics fill with air after hours on highway. Replacing the flex hose that was damp with brake fluid fixed it.

    Paul Shovestul



    Quote Originally Posted by DanDombrowski
    .....What I'm saying is that I don't understand why it will have air in it/lose pressure on the highway, but when it sits overnight it doesnt?
    Last edited by Bellicose Right Winger; 11-02-2005 at 07:11 AM.
    .....Got to keep the loonies on the paath.

  7. #7
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    Default

    Interesting observation, I was thinking it was something along those lines (my first guess was to rule out a 2 year old MC vs a 15 year old hydrualic hose), but I value the experience of Bill, Winfred, and the other experts over my hunches.

    I figuring that is has to be a vibratory problem; there must be a very small leak that allows air in after small amplitude vibration on the highway over extended time, thats the easy part. Now, its been dry this morning (the weather, not the clutch, haven't checked) so mabye tonight I can get underneath the car, that is if I can get out of work and get home by the time it gets dark-freakin time change.

    At Bill: The level isn't what I would call perfect, but no different than usual. That was the first thing I checked when I got to where I was going on the highway, it was about halfway between min and max. I added the rest (not much) of a spare bottle I have in the trunk, the level didn't change a whole lot. I've always had a little seepage at the seals of the brake fluid resivoir, but if I were pulling in air there, it would affect the brakes too, no?

    At Right winger: Sounds like I'm encountering your symptoms. What I cant wrap my head around is how the air gets OUT when you pump the pedal unless its bleeding itself. Through the same leak? I suppose that if the leak were at a high point and the air could get to the top, the pressure would force the air out.... That would have to be a REAL small leak not to loose pressure when the pressure of the clutch is applied and not lose all the fluid.

    The other thing I don't understand is why it might not be the MC. Air in the system is air in the system, no matter how it gets in or out. I'll get underneath there and look, and probably replace a hose or two anyway while I'm in there first, then go with the MC if that doesn't fix it. Problem is, come January, my girlfriend moves down to west palm with me, and my weekly commute to gainesville will be over, so I might not see the problem for a while unless it propagates.

    Also at Right Winger: How was that MGB? I've always wanted an expensive go-kart to tool around in on the weekends, but wanted to hear from someone who owned one. What was its primary use, and would you get one again?
    93 525i / 01 330Ci / 98 Camry / 91 Volvo 240 / 99 Jeep GC

  8. #8
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    Minneapolis, MN
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    Default

    a little late to this boat.. but ive had this exact same problem. it occurred many times over the summer, to the point where drove the last couple miles home w/no clutch. the next morning id go out, everything would be peachy.

    i assumed it was some sort of overheating? in the clutch line because it stopped occuring as soon as the weather cooled this fall. kind of wondered how it didnt affect the brakes, though.

    replaced the clutch and master cylinder summer 04, master and slave summer 05 when this problem came up. had it pressure bled in a shop each time. almost went nuts when a week after replacement of both cylinders it did it again. now i have a spare master sitting on the shelf, just in case.

    ill check that flex hose tonight..
    -Pekka

  9. #9
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    Default

    This problem is commonly reported on the E34 M5 board. Check the breather in the MC cap is open.
    Anthony
    03/64 production

    '91M5 - 11/90, was mine, it's Jim's now.

  10. #10
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    Default

    sorry anthony.. dont really understand. where is the breather cap on the master cylinder? or do you mean on the brake fluid reservoir?

    Quote Originally Posted by Anthony (M5 in Calgary)
    This problem is commonly reported on the E34 M5 board. Check the breather in the MC cap is open.
    -Pekka

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