Now the clutch works... now it doesn't.

[SLOroadster]

I have been dealing with a phantom clutch issue since the beginning of the month. I replaced the master cylinder for the 2nd time in 2 years, and now it works sometimes, and sometimes it doesn't. Its not leaking from the slave (replaced 2 years ago), the fluid level doesn't change, and the clutch its self has less than 3k miles on it. It will work at one stop light just fine, the next I have to start it in gear and hope it is willing to work for the next shift. I don't really like chewing up gear boxes due to some stupid thing, but I'm out of ideas. The system is well bled, and feels great when it works, but when it doesn't work, the pedal goes to the floor and nothing happens.

Any ideas?

thanks,
Will

[TR]

If the fluid level isn't dropping, and sometimes it works fine, the next time there is no resistance in the pedal, it sounds like the valve that allows fluid back into the reservoir is not actuating properly...Clean/rebuild/replace the master...TR

[Scott Smith]

This is probably not your problem but I wanted to share anyway.
I was working on a hydraulic clutch the other day and had the same sort of problems. Turned out that the rubber thing attached to the cap came un-attached and was sitting in the reservoir. The fluid level was full but sitting on top of the rubber thing. Boy did I feel stupid when someone else pointed this out to me??
Sounds to me like the slave cylinder is letting fluid past the plunger when under pressure. You can usually diagnose this if at a stop light with clutch depressed clutch slowly engages.

[toolsnob]

I had the same problem on my 73 LC, sometimes I would be stopped at a light and the clutch would just engage while I had the peddle down. This is clearly a hydralic issue. The best way to solve the issue is to replace all hydrallic parts, which I did and never had another moments issue with it. It may set you back $200 to change it all out but well worth it.

[Dustin]

I recently conquered my phantom clutch problem that began over a year ago finally resulting in 2 master cyl rebuilds, a new slave cyl, 2 engine removals, a new clutch and a lot of sad drives. The source of all the madness was that good old clevis pin. The pin and the pedal will oval out to the point of only fully engaging the master cyl piston at a certain spot which did several things to my roadster.
1. impossiable correct free play adjustment. It will either slip or grab too fast leading to an early clutch replacement and awful in town driving
2. put uneven pressure on the master cyl rod, ruining the seals on your piston and leaking onto the floorboard.
3. affected my idle, I don't care what anybody says, it did.

make sure your pedal linkage is squared away FIRST. I ended up drilling a larger hole and using a new pin from home depot, plus inserting washers in the gaps on either side of the fork (the inside gaps) to make sure it's not cocking to one side when engaging. one way or the other, the travel of the master cyl piston must be full and the same at all times. I would almost garantee this is your problem. From stoplight to stoplight the piston rebounds erraticly, sometimes barley. this can make your pedal feel nice and stiff then at the next light, mushy nothingness. try pressing the pedal in and releasing it quickly, pumping sort-of (let it snap back to un-jar it). I have even had to tap (hit) the master cyl housing with a wrench to unstick it. you will be able to feel it regain pressure as the piston returns fully. then make sure the fluid is nice and clean and bleed both cylinders like ,,? a bleeder guy-ish would. then adjust your free play. Make sure the slave cyl piston is as far towards the rear of the car as possiable BEFORE adjusting. Not taking off the spring when adjusting free play can do weird things.

Take care of this BEFORE it becomes an engine pull.


or
your master cyl inside may be too large from overbuffing when you rebuilt it, not allowing a good seal and leaking by. but I doubt it

[S Allen]

Yeah Will, I think doperide may be on the right track. The worn clutch rod and or clutch pedal can cause all kinds of clutch problems. Doperide's fix sounds like it would work. Many people pull the clutch pedal, weld the hole closed and then redrill it. Let us know if it is in fact a worn clutch pedal or clutch rod or a combination there of. Good luck. We need to do a run real soon. I have been busy with other pusuits but really want to get a run together. We have some geat roadster roads in Sonoma, Napa nad Lake Counties.

Steve

[TR]

Doperide does have a great observation...If the linkage is loose, the master piston assy may not be reurning far enough to let the little valve return to the "pressurize" position.

Wasn't Joaquin having the same issue? TR

[SLOroadster]

No play at the pedal end. It seems to be ok for a little while, but it goes soft after 10 minutes of driving. But it will come back, or the issue will not show up at all. Its very strange. It will start soft, but firm up later.

Its working now so I'm not going mess with it.

Will

[TR]

Will,

Having something, then nothing points to the master.

Having soft build to firm with pumping is air in the system.

The easiest way to check for air in the clutch hydraulics is to place a zip tie over the slave to stop its travel. Push slowly. If the pedal is mushy, building to firm and then snaps the zip tie. You have air. If the zip tie snaps before you feel any pressure, look elsewhere...

[SLOroadster]

Its a brand new Tokico master cylinder. I just replaced it because it didn't work at all.

Will

[dbrick]

Do any of the fluid lines run close to the exhaust? Heat can do wierd things to brake fluid.
Also, can a new master require more or less shims than the original, not allowing full retraction of the cylinder, or would the freeplay adjustment take care of that?

[SLOroadster]

Ok I have bled this thing twice and it is still causing issues, the trip down to Blackhawk was uneventful, the trip back was a nightmare. There is no fluid loss, the master cylinder is new, the slave is 1.5 years old. The only thing left is the rubber hose. I need to get this thing figured out before I put another 800 miles on it next weekend. I have to still have air in the system somehow. This is driving me up the wall.

Will

[TR]

Will, are you totally sure your master is returning all the way? Is the actuator rod at an angle or anything? Is this a stock master? You may try taking the pin out and pulling the rod toward the pedal. When both are pulled, adjust untill the hole in the bracket aligns with the hole in the pedal arm.

[toolsnob]

it has to be something simple and over looked. Are you using a rebuilt master or a new one? The old master had an unadjustable clevis and you used shims to adjust the throw. Some of the new units have and adjustable clevis and you can throw out the shims and adjust the clevis down till it matches your brake master. I have installed 3 three masters this year into 3 different cars and have not had one moment of trouble. I don't think it is the slave, it either works or leaks. If you are not having a fluid loss it has to be the Master cylinder, are you sure the pin is not wore where the clevis meets the peddle? Do you have a return spring on the clutch peddle arm?

[dbrick]

A porous hose could be it, but I would guess it would either look real bad or leak. Mine looked ok, til I bent it and it cracked in 10 or 12 places. They can also shed rubber from the inside of the hose which can clog things up. did you get anything odd in the fluid when you bled it?

If it's feasable, just change the hose, bad or not. I think it needs a copper crush washer at the slave, but not sure. I believe this is still avail at dealer.

Is it a stock Nissan, you said Tokico, is it an exact replacment? I'm asking because I may have the same one, from Vera.

The procedure I used to use on my Fiat X 1/9was to block the clutch lever with a clamp or piece of wood to build pressure and then bleed it like brakes. That car had a long fluid line and was hard to bleed.