A clutch question for bill R or winfred

[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 :(.

[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.





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 :(.

[winfred]

that about covers it


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.

[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?

[Bill R.]

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








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?

[Bellicose Right Winger]

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




.....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?

[DanDombrowski]

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?

[peks]

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..

[Anthony (M5 in Calgary)]

This problem is commonly reported on the E34 M5 board. Check the breather in the MC cap is open.

[peks]

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


This problem is commonly reported on the E34 M5 board. Check the breather in the MC cap is open.

[Bellicose Right Winger]

Do these symptoms occur on every trip to Gainesville?

It's not uncommon for the clutch hydraulics to be self bleeding. The clutch tubing has no pockets so the air bubbles will rise up to the MC and into the reservoir. Pumping the pedal helps also.

I don't think it's the MC because the clutch is fine in the morning. Low clutch pedal engagement in morning which returns to normal after a few shifts is classic internal leakage at MC. Also the MC is inside the vehicle and subject to the same conditions whether you're driving in town or on the highway.

The leak at the reservoir can starve the MC of fluid, but your reservoir was never low enough for this to happen so it doesn't explain your symptoms. Changing the grommets under reservoir should fix this and keep paint on the frame rail that the leaking fluid is eating away.

Anthony (M5 in Calgary) may be onto something. While I can see how an unvented reservoir could create all sorts of strange problems, I can't explain why hours on the highway would make it worse then driving in town. Checking this is easy, simply loosen cap before your next trip.

The 1963 MGB was an $85 car in 1971 when I was senior in HS. It needed engine work and was quite a valuable education in mechanics for this (then) future mechanical engineer. I drove it 300 miles to college a half dozen times freshmen year. It was replaced with a V6 Capri. After driving a german auto though there's no going back. If you want a go-kart, I'd suggest an E30 325iM. The convertible versions seem to be reasonably priced these days.

Keep us informed of your progress.

Paul Shovestul




.........
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?

[DanDombrowski]

They've only shown up on my last trip up. On the way up I noticed it and thought, "Now thats odd. Its like the clutch is on the floor....." after a few shifts, I wasn't sure if I was imagining things. I also had on bigger than normal shoes. I drove it around the next day, all is well. Even did some pretty spirited launches just to check- everything fine. On the way home, I definitely felt the same thing going through the toll booth, but each time, it took me by suprise. So, again, I get home (to WPB), drive around a little, all seems ok, although the clutch was a little low. I didn't really remember how high the clutch was to begin with, so I still wasnt sure if it was all in my head. Just yesterday I thought to check, and sure enough, the clutch is hard from the very top, so it was definitely low before.

I checked it this morning too, hard as a rock. I've been planning on doing the grommets on the resivoir for awhile. I think I might get a new resivoir too for the "newness" look of it, it'll help when I sell it :)

When you say MC cap, you mean the brake fluid resivoir cap? Thats never been a problem before, but I'll check it.

Supposedly, the fluid can get too low for the clutch before it gets too low for the brakes, so I think my plan of action is to check under the car tonight (if its still light out), fill the resivoir pretty well, and see what happens on my drive up this weekend. Thanks for all the help guys, I'll let you know what I find out.

Oh, and the e30 325iM was the car I was looking for originally, but people wanted wayyyy too much for them, so much that I found my 93 e34 for the same price as most wanted for an 89 e30 vert.

I already know my next car is going to be an e36 m3 convertible or an e46 330i convertible, whichever car presents itself sooner. I've already got the cash lined up, just have to find the car, so having 2 3 series convertibles, while a dream come true for some, isn't what I was going for. I thought it would be a fun thing to take to the beach, roast the tires for the fun of it, and be one guy with a 'different' car.

Its a really good thing I can't get to ebay at work, or I'd be lookin at em all day long.

Take care,