No Visible Leakage from Clutch Slave Cylinder?

[73ess]

Recently the clutch pedal on my '88 Cabriolet has not been coming all the way back up, after depressing it. The brake fluid warning light was flickering at the same time as this was occurring. Then one morning I went out to the car and the clutch pedal dropped to the floor when depressing it and I couldn't shift into first. So....I checked the fluid level and it was at the MIN mark. I'm fairly certain it's a bad slave cylinder, but I jacked up the car to view the slave and it looks clean with no signs of leakage anywhere on it's exterior. Perhaps the only way to visibly see leakage is after removing it? Maybe it's leaking behind the mounting bolts? But I don't see any fluid on the floor under the car either. Clutch master cylinder looks dry, so it's gotta be the slave, right? Brakes feel fine.

[Green 912]

IIRC on your year car the clutch and brakes use the same tank and the clutch takes its fluid off the tank about 1/2 way up. If you let the brake fluid drop down below the clutch intake you can let air into the clutch system. Try refilling the tank and bleeding the clutch system. Bleeding the clutch can be a frustrating ***** unless you do it right and even then it is still a standard *****. You need to flush the system out till it shows no air in the fluid coming out then shut off the flow and pump the clutch pedal like mad for 20 seconds or so. This will mix any remaining air that is trapped in the slave above the bleed nipple into the fluid in small bubbles than can be carried out as you bleed the clutch a second and then third time. Keep frothing and bleeding until it comes clean. A Motive pressure bleeder is a big help in flushing the clutch but be careful to keep the fluid level above the clutch take off point on the fluid tank.

[73ess]

Thanks I'd try your suggestion, but I must have a leak somewhere to cause the fluid to drop that low. I'd like to track the leak down. I guess I'll pull the slave and see if there is leakage at the pushrod. I've jacked up the driver side of the car. Doesn't look like it'll be all that tough to get to the slave, but then I've got pretty skinny arms and hands.

[Thomas Owen]

You could still have a leak in a brake cylinder out at one wheel. As mentioned, the clutch master pulls fluid from the top of the reservoir and the brake master slightly lower.
One other possiblity is severe brake pad wear for some reason (been to a track?) allowing the brake wheel cylinder to expand and pull in more fluid from the reservoir. So, it does not have to be a leak...but check the brakes before pulling the clutch slave.
Good luck -

[73ess]

Ok. Will do. I'll check all the calipers first and make sure they're dry.

[88911coupe]

I had the same problem but NEVER saw my fluid level drop and could never find ANY evidence of leaks. I ended up replacing the clutch master cylinder first hoping that would fix it but no such luck. Then did the clutch slave cylinder and that fixed it. I think what was happening was the fluid would get past the worn seals resulting in no pressure and then it would flow back around the seal when I pulled the pedal up. It would often drop nearly to the floor and then when I'd pull it back up it would work fine for days at a time then drop back...usually in the morning when it was cold. The bottom line is I never leaked any fluid.
Good luck,

[rnln]

when my slave leak/bad, I saw oil leak along the bottom of the tranny, right at the gap between 2 housing, and also the fluid level in the resevoir is at the min mark. THink about it. When your slave leak, it will leak at the tip. That means it leak inside the tranny bell housing. You won't see it on the slave housing (ouside the tranny).
When you take the slave off, ask someone to step on the clutch while you hold your slave in your hands. Fluid spray out at the boot. Becareful, you might get it spray right at your face. Ask me how I know.

[Green 912]

Pad wear will lower the fluid level. A fluid leak that is enugh to drop from full to 1/2 full would be easy to find for the most part.

[Quicksilver]

If it is leaking at the slave cylinder the fluid will be inside the bell housing. If it is leaking at the clutch master the fluid would be under the pedal foot board. If the brake master is leaking it would be going into the vacuum assist unit. Lots of places to hide fluid.

It really sounds like it is a low fluid problem but I would pull up the board under the pedals and make certain that the pedal is still moving the clutch master cylinder. You can also check the clutch master for leaking.

If that comes up clean you can loosen the brake master from the vacuum assist can and see if it is wet there. If that isn't it you probably need to look at the clutch slave and that is a pain.

[M Scahfer]

my clutch pedal did the same thing about 18 months ago, bought master and slave cylinders, but first cleaned the entire pedal assembly with no help. then replaced the master because it is easier than the slave. works like new. i would highly recommend the power bleeder for the clutch circuit it is very hard to clear the air without one. still have a brand new slave waiting in the parts drawer.

[Quicksilver]

Originally posted by M Scahfer
my clutch pedal did the same thing about 18 months ago, bought master and slave cylinders, but first cleaned the entire pedal assembly with no help. then replaced the master because it is easier than the slave. works like new. i would highly recommend the power bleeder for the clutch circuit it is very hard to clear the air without one. still have a brand new slave waiting in the parts drawer.

Even with a power bleeder the clutch is a pain. I have found it easier to remove the slave from the tranny and bleed it with wile it is hanging down. This way you can insure that the bleeder is in the top corner while bleeding.

It is a real pain bolting the slave back up but I always get a good bleed on the first shot which never happened before.

[88911coupe]

Well...did a search and found my post on this subject and the movie is playing again. My clutch pedal is occasionally sinking a little and if I pull it back up it works fine. We've gotten some really cold weather (for Dallas at least) and this seems to make things worse. I'm not losing any fluid so I assume the seals are allowing fluid to get by. Here's my question...is there any way to tell whether it's the master or slave cylinder? Last time I replaced the master first and it was the slave that was the problem...should I assume its the same this time? Which one is working harder....I assume it's the slave cylinder which is also more exposed to the elements.
Thanks

[Chuck.H]

Probably not your problem, but worth checking - the cross shaft that the clutch pedal rides on broke on my '89 at around 200k miles. Funny thing is it cracked and held on for months with a spongy, sinking pedal feeling. Even when I replaced it, it was still operational, but cracked down the center like a stick pretzel, and almost split into two.

Pelican came thru and got me a new OEM one from Germany even though it was NLA. (do I get the job Mark? :-))

Chuck.H
'89 TurboLookTarga, 385k miles

[3literpwr]

Happened to me this summer on my '87... I first thought it was the master as it was wet with fluid, but it turned out to be the slave. I also didn't see any leakage from the slave.
I used my motive bleeder after replacing and it worked great. Still a total pain to get to the slave cylinder.

[kidrock]

chances are that if you are losing pedal but not fluid, bleeding the slave may solve the problem. Accessing that bleeder nut is a PITA.

I replaced my slave about 6 months ago, I was losing fluid in my brake master cylinder. After a couple of days of scratching my head, I noticed about 3 days later that the fluid was running onto my garage floor from under the engine.

After I replaced it and started the bleeding process, I couldn't figure out why I wasn't getting any fluid to flow during bleeding, but eventually learned that I needed to turn that nut just another fraction did the trick. Probably the least pleasant job I've done on this car to date.

[thethrill]

If there is not visible leakage and the clutch fork has not been upgraded it is most likely worn needle bearings on the clutch fork. As the bearings wear extreme pressure is put on the pedal Assyrian and clutch fork. Something eventually breaks. Either the bosses on the trans or the pedal assembly.

I had 3 pedal assemblies (shaft in the pedal assy) break before it was fixed correctly. Fix the cause not the symptom. When doing the clutch fork upgrade I would suggest replacing the pedal assembly cross shaft. After you do this your clutch will feel normal.

Good luck.

[88911coupe]

I have the upgraded clutch system so that's most likely not the issue but good suggestion. I think I may have an idea which may be causing the issue...I have wondered about how to set the clutch pedal travel limit on my car. There is an adjustable stop and I wonder if I have it set TOO far and maybe that is causing the slave cylinder to wear out it's seals early? I have never really gotten a good desription of exactly how far is sufficient for the clutch pedal and how far is TOO far.

[Chuck.H]

if your clutch is fully released and you can still press the pedal a lot farther, then it's adjusted too far. I like to set mine to just a little past fully released, and then I use it often, ie I floor the clutch pedal to the stop (and shift gingerly... not the fastest shifts, but my transmission is all original, including the syncro's.)

Chuck.H
'89 TurboLookTarga, 385k miles