Clutch Master Cylinder

Synchros shot? Weird noises while shifting? Not sure what needs to be replaced?
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Re: Clutch Master Cylinder

Postby Rope-Pusher » Fri Dec 25, 2015 11:34 am

potownrob wrote:wait what happened here?? there seems to be a gap in what happened in this thread. :o :? 8)

I bet that's what happened to this site's missing members - they fell into the gap!
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Re: Clutch Master Cylinder

Postby bk7794 » Fri Apr 22, 2016 9:59 pm

Finally got around to fixing this. I put about 7500 miles on the old master cylinder since I've noticed the leak. I filled up the reservoir once. Still worked and I didn't loose my clutch. Definitely was in need of replacing and replacing the fluid really did wonders. The pedal is light and quick now.

Thing that sucks is adjusting the hydro clutch travel.
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Re: Clutch Master Cylinder

Postby InlinePaul » Fri Apr 22, 2016 11:46 pm

bk7794 wrote:Thing that sucks is adjusting the hydro clutch travel.


Ummm, from the hydraulic clutch setups I have had in recent years (concentric slave) the only way to adjust travel is to shim the flywheel to change the clearance slightly. The big drawback to hydraulic clutch is lack of functional adjustment (can't be dropping the tranny to adjust) and lack of easy way to bleed the master. I liked my 1984 F150 as it had hydraulic clutch with the old clutch fork and a slave on the outside of the tranny. You could change out the clutch and never disturb the hydraulics. Now I have this funky self adjusting clutch disk that keeps my engagement almost at the floor, no chance for it to come up from wear.
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Re: Clutch Master Cylinder

Postby theholycow » Sat Apr 23, 2016 8:48 am

InlinePaul wrote:lack of easy way to bleed the master.

Unless the hydraulic line is shaped like a Krazy Straw...

Image

...there is an easy way. Just remove the cap from the reservoir and pump the pedal 20 to 150 times. Air bubbles will work their way up and out.

While you're at it you might as well use a turkey baster to remove existing fluid from the reservoir and refill it with fresh stuff for a partial fluid change. You'll see the cloudy old fluid from below infiltrate the clear new fluid and, if you want (since brake fluid is cheap), you could repeat the partial fluid replacement to get more of it.

I liked my 1984 F150 as it had hydraulic clutch with the old clutch fork and a slave on the outside of the tranny. You could change out the clutch and never disturb the hydraulics.

Also, changing the slave cylinder is a whole lot easier!

However, the concentric slave cylinder is graceful and simple...and if it's made well then it's sure to never need replacing (but if not then you gotta drop the trans!). The fork-and-slave is a more complex system with more parts to fatigue/fail/have friction/maladjust/rust/misalign/etc, and (depending on just exactly HOW external that slave cylinder is) it might take up space that could be used for something else (headers anyone?).

The 1986 S10's external slave was just barely inside the bellhousing, with an access panel on the outside; it was out of the way. The fork was entirely contained inside the bellhousing. In this photo you can see the entire fork and on the right side there is daylight through the rear of the bellhousing where the slave mounts.
Image

My DIY adaptation is rather less graceful. Photographed from underneath the car, the ugly slave bracket is easily visible in the upper left corner of the photo, with the fork sticking out of the bellhousing in the center of the photo and the rusty buttress that I recently added running diagonally from the slave bracket to a fin on the T5 in the lower right of the photo. You can also see the business end of the slave cylinder mated to the fork, along with the rubber boot/bellows that protects it, and looking to the left of the bracket you can see part of the slave cylinder's main body.
Image

Headers are definitely never going to happen...not that it would be fast with them anyway. I've seen photos of many similar setups that are less bulky but still exist in the same general place.

Now I have this funky self adjusting clutch disk that keeps my engagement almost at the floor, no chance for it to come up from wear.

I like floor engagement. Even better would be if the entire stroke was shortened so the pedal is closer to the floor when fully engaged.
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Re: Clutch Master Cylinder

Postby Rope-Pusher » Sat Apr 23, 2016 9:30 am

The hydraulic release system adjusts itself every time you take your foot off the pedal - the master cylinder piston retreats as the pedal comes up and the reservoir port in the side-wall of the cylinder is uncovered, allowing fluid to come and go as necessary.

If you don't like the adjustment, i.e. the clutch release function vs pedal travel is not to your liking, you really need to pick apart the design. If you want more pedal reserve, i.e. more room between the engagement position and the pedal downstop, then you can either lower the downstop or raise the upstop.
Image
Pretend you are a foot and spend some time down by the pedals - see what would keep the pedal from coming up any higher...maybe the master cylinder acts as the upstop. Could you lengthen the master cylinder input rod? Then, the pedal would start higher and potentially end at the same downstop, resulting in more master cylinder piston travel and more slave cylinder travel to move the release and engage points further off the floor.

Sure, you could also dive deep and try sustituting a different master cylinder with a larger piston bore,...but then you are dealing with space constraints, cylinder mounting methods, clutch line connector dissimilarity, etc.
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Re: Clutch Master Cylinder

Postby InlinePaul » Sat Apr 23, 2016 9:39 am

theholycow wrote:
InlinePaul wrote:lack of easy way to bleed the master.

Unless the hydraulic line is shaped like a Krazy Straw...

...there is an easy way. Just remove the cap from the reservoir and pump the pedal 20 to 150 times. Air bubbles will work their way up and out.


I find it hard to believe it would be that simple and the shop screwed around with the truck for two weeks! It was well timed because I was off work with pneumonia the same time and so didn't need the truck. So I think there may be still the slightest amount of air in the system (master, slave or wherever) as the pedal engagement sometimes is lower in certain weather conditions. If I go unscrew the master cap and pump pedal like a mad man stomping a rat, you say the air will come out? Why doesn't the air come out with the cap on then? Wouldn't the bubbles work their way up either way, the are after all seeking higher elevations?


While you're at it you might as well use a turkey baster to remove existing fluid from the reservoir and refill it with fresh stuff for a partial fluid change. You'll see the cloudy old fluid from below infiltrate the clear new fluid and, if you want (since brake fluid is cheap), you could repeat the partial fluid replacement to get more of it.


What about a crazy straw and spitting it into a bucket? Image But Yah, i have done the turkey basterd stuff to the power steering before, I even have syphoned out the pan load of the ATF before.

Now going back to the slave, i had slave replaced in Feb 2014, he said clutch looks good for at least 20K more miles so we left it alone. But he failed to replace the throwout and so one year later to the date the throwout died, locking the pedal in the up position. You would have needed a hydraulic jack to depress the pedal. I drove it no clutch shifting trying to get there but was bad traffic and a guy towed me last half mile. Wish shop would have said in 2014 Hey lets do the throw out too for good measure.
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Re: Clutch Master Cylinder

Postby InlinePaul » Sat Apr 23, 2016 9:46 am

Rope-Pusher wrote:The hydraulic release system adjusts itself every time you take your foot off the pedal - the master cylinder piston retreats as the pedal comes up and the reservoir port in the side-wall of the cylinder is uncovered, allowing fluid to come and go as necessary.

If you don't like the adjustment, i.e. the clutch release function vs pedal travel is not to your liking, you really need to pick apart the design. If you want more pedal reserve, i.e. more room between the engagement position and the pedal downstop, then you can either lower the downstop or raise the upstop.

Pretend you are a foot and spend some time down by the pedals - see what would keep the pedal from coming up any higher...maybe the master cylinder acts as the upstop. Could you lengthen the master cylinder input rod? Then, the pedal would start higher and potentially end at the same downstop, resulting in more master cylinder piston travel and more slave cylinder travel to move the release and engage points further off the floor.

Sure, you could also dive deep and try sustituting a different master cylinder with a larger piston bore,...but then you are dealing with space constraints, cylinder mounting methods, clutch line connector dissimilarity, etc.


We took out the ~1/8-inch rubber pad from the pedal stop for more travel. No adjustment otherwise. From dead start it will start rolling truck forward as little as 1/2 inch off floor, sometimes less. But I feel the main engagement about midway up pedal Top of pedal fine plenty of pedal above engagement, prob 1.5 inches anyway. On freeway in high gear I gave heavy foot on accelerator and depressed clutch slowly, engine revved up with pedal still about 2 inch off floor so it seems engagement is lower but disengagment higher. It is funky but working so like to leave well enough alone, but want to go out now and try Cow's air bubbles with cap off thing.
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Re: Clutch Master Cylinder

Postby theholycow » Sat Apr 23, 2016 11:49 am

InlinePaul wrote:I find it hard to believe it would be that simple and the shop screwed around with the truck for two weeks!

I suspect that it is not well known or well documented, but it definitely works for me. It worked when I accidentally broke and spliced my clutch line, and again when I replaced my slave cylinder.

If I go unscrew the master cap and pump pedal like a mad man stomping a rat, you say the air will come out?

I pump somewhat steadily, not stomping like a madman but not too slowly. I expect that too much excitement could agitate it and introduce more air or split large bubbles into smaller ones.

Why doesn't the air come out with the cap on then? Wouldn't the bubbles work their way up either way, the are after all seeking higher elevations?

I never bothered to analyze it since it was working so well for me. Maybe something something air pressure something something?

Now going back to the slave, i had slave replaced in Feb 2014, he said clutch looks good for at least 20K more miles so we left it alone. But he failed to replace the throwout and so one year later to the date the throwout died, locking the pedal in the up position. You would have needed a hydraulic jack to depress the pedal. I drove it no clutch shifting trying to get there but was bad traffic and a guy towed me last half mile. Wish shop would have said in 2014 Hey lets do the throw out too for good measure.

Yeah, he should have suggested it. The decision comes down to risk manglement I guess. When you're paying someone $150/hr it makes sense to drop in a $30 release bearing while it's apart, and IMO with an estimate of 20,000 miles left I would have thought it silly not to replace the clutch too.

When you're doing it yourself in the backyard and your budget is always a problem, saving $30 on a release bearing is a little more attractive -- but even I went ahead and replaced it. Granted, before taking it apart I thought the release bearing was to blame for a symptom I had, so I already had the new one in-hand. OTOH I put in a used clutch disc that I had in stock rather than buy a new one for $80.
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Re: Clutch Master Cylinder

Postby Rope-Pusher » Sat Apr 23, 2016 12:21 pm

There really ought to be a way to bleed the clutch line down to a point near the bellhousing - even with a concentric slave cylinder. On some of our products, you push a clip and partly disconnect the fittings, which uncovers the bleed port. You can then put a clear tube on the bleed port nipple and let if spew into a container and watch for bubbles to stop coming through the clear tube - you might not even need to have someone step on the pedal for you, because with the pedal up that clutch master cylinder reservoir port should be open and gravity should move fluid downhill from the reservoit to the bleed port.

On pumping - sometimes, there is no way to bleed through to the far end of the hydraulics. By bleeding the top half, closing the bleed port, AND THEN GIVING THE PEDAL 50 - 100 GOOD SLOW PUMPS, any air down at the slave cylinder will come up through the lines far enough that a second round of bleeding will dispel it.

After bleeding, always top off the reservoir...exspecialty if it is also the brake fluid reservoir!
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Re: Clutch Master Cylinder

Postby IMBoring25 » Sat Apr 23, 2016 10:51 pm

InlinePaul wrote:Now going back to the slave, i had slave replaced in Feb 2014, he said clutch looks good for at least 20K more miles so we left it alone. But he failed to replace the throwout and so one year later to the date the throwout died, locking the pedal in the up position. You would have needed a hydraulic jack to depress the pedal. I drove it no clutch shifting trying to get there but was bad traffic and a guy towed me last half mile. Wish shop would have said in 2014 Hey lets do the throw out too for good measure.


That rings a bell. I bought my truck with a "new clutch" in it. It ultimately became blatantly obvious they didn't do the pilot bearing at the same time when it basically turned to dust and required me to drive home 30 miles almost clutchlessly.

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Re: Clutch Master Cylinder

Postby watkins » Tue Apr 26, 2016 1:09 pm

Rope-Pusher wrote:There really ought to be a way to bleed the clutch line down to a point near the bellhousing - even with a concentric slave cylinder. On some of our products, you push a clip and partly disconnect the fittings, which uncovers the bleed port.

I would like to smack whoever was the asshole who designed that system. Bleeding a clutch in a Dart is a major pain in the ass.
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Re: Clutch Master Cylinder

Postby Rope-Pusher » Tue Apr 26, 2016 11:09 pm

watkins wrote:
Rope-Pusher wrote:There really ought to be a way to bleed the clutch line down to a point near the bellhousing - even with a concentric slave cylinder. On some of our products, you push a clip and partly disconnect the fittings, which uncovers the bleed port.

I would like to smack whoever was the asshole who designed that system. Bleeding a clutch in a Dart is a major pain in the ass.

The system came to us from the FIAT side of the house, but I was the guinea pig for writing down the bleed procedure and teaching it to folks at Belvidere Assembly plant when the Dart pilot vehicles were first being built....and I thought it was not an uneasy process. I just wish there was a way to bleed it all the way out thru the slave cylinder instead of at the connection just outside the bellhousing. That would eliminate pedal pumping and secondary bleeding afterward.
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Re: Clutch Master Cylinder

Postby bk7794 » Wed Apr 27, 2016 9:28 pm

The adjustment I was talking about is the pedal freeplay. So the shaft for some reason isn't default against the piston. You need to turn the rod until an undetermined feeling is reached, this is presumably where the pedal rod comes in contact with the piston itself. Then you back it off an undetermined amount...(a smidgen) and then you have a fully functioning pedal. Right now my contact point is too high...and the whole contact point feels like mud.


So this is the second time working on the car in the last few months...second time I got sick while doing it.
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Re: Clutch Master Cylinder

Postby watkins » Thu Apr 28, 2016 11:13 am

Rope-Pusher wrote:
watkins wrote:
Rope-Pusher wrote:There really ought to be a way to bleed the clutch line down to a point near the bellhousing - even with a concentric slave cylinder. On some of our products, you push a clip and partly disconnect the fittings, which uncovers the bleed port.

I would like to smack whoever was the asshole who designed that system. Bleeding a clutch in a Dart is a major pain in the ass.

The system came to us from the FIAT side of the house, but I was the guinea pig for writing down the bleed procedure and teaching it to folks at Belvidere Assembly plant when the Dart pilot vehicles were first being built....and I thought it was not an uneasy process. I just wish there was a way to bleed it all the way out thru the slave cylinder instead of at the connection just outside the bellhousing. That would eliminate pedal pumping and secondary bleeding afterward.

Whats wrong with a simple bleed screw? Or if we have to use that stupid disconnect, why not use a more easily released fitting? That metal release tab thing is painful after the third time you press it.
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Re: Clutch Master Cylinder

Postby theholycow » Thu Apr 28, 2016 12:43 pm

watkins wrote:That metal release tab thing is painful after the third time you press it.

Requires SST 1548734165741, available from Hard To Reach Inc for $485,174 and your firstborn.
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