Baffling clutch behavor

THE PROBLEM: intermittently (typically days between occurrences) when my 1989 Nissan Stanza has been sitting (not running) for awhile depressing the
clutch pedal has no effect: I start the car in neutral but cannot shift into gear. If I pump the clutch pedal a couple of times then all works perfectly from there
on (e.g., I can drive only 50 feet, so nothing has warmed up, and can easily shift into second, etc.). The problem is only on initial start-up, never on
subsequent attempts to shift.
ATTEMPTED SOLUTION: I replaced the slave cylinder; I had a shop replace the master cylinder. The problem persists.
MORE INFORMATION: I replaced the clutch well over a year ago and it worked perfectly until a month ago; there is no apparent pattern: the problem occurs only every few days, sometimes when the car has sat for only a couple of hours, sometimes when it has sat for a couple of days, and it can sit for
four or five days but work perfectly. Finally, once I get it working (by pumping the pedal a couple of times, if need be) it all works perfectly: firm pedal,
quick pedal return, smooth shift with no grinding of gears—perfect.
THE QUESTION: what in the world is going here?! It makes no sense to me.

I had a problem similar to this with one of my cars. It was intermittent at first and then after a while I had to start the car with the transmission in gear, hopefully on a downward slope. Was on a camping trip 1000 mi from home, but was able to limp it back. What happened was that one of the springs on the friction plate failed and parts of the spring would get in a place that would not allow the clutch to disengage. I did not find out what was the actual problem until I had the transmission pulled out. I had thought it was a failing pilot or throw-out bearing originally.

It puzzles me too. You did have the shop replace the CLUTCH master cylinder, right? Have you checked the fluid level in the clutch master and slave cylinders? Have you had someone work the clutch while you look and see that nothing is moving that shouldn’t?
If the answer is yes to everything, the only thing I can think of is that one of your new cylinders is bad.
{ am wondering if bad motor or transmission mounts or loose engine to transmission bolts could cause this but I can’t figure out how.

When this happens and depressing the clutch pedal has no affect, does the clutch pedal go to the floor with little or no resistance or does it feel normal but just does not disengage the clutch?

If the latter, the clutch plate is sticking to either the flywheel or the pressure plate. I suspect that it isn’t the conditions of start up that contribute to the but the conditions near the end of the last drive. The clutch was used a lot just before shut down and the resins got hot enough to adhere to one side or the other during cooling. The bond isn’t strong so a couple of jabs breaks it free.

And, just to echo @oldtimer11, new parts can go bad. It’s why they have warranties. I replaced the slave and master in my car, and the slave started leaking within 30 days. I had to remove it and get a replacement under warranty.

OK the case against it being hydraulic, he has the problem, changes both cylinders, problem persists. Replacing them again is like the definition of crazy, repeating something and expecting a different outcome. I like hikers answer if the pedal goes to the floor easily. I had something similar when a flywheel bolt broke and the head got stuck between the clutch plate and the flywheel.

Keith asked:
When this happens and depressing the clutch pedal has no affect, does the clutch pedal go to the floor with little or no resistance or does it feel normal but just does not disengage the clutch?
The answer is:
The pedal feels normal every time, whether things are working right or not.

The clutch pedal force can seem ok, even though the hydraulics are leaking, unless there is an obvious visible leak at the slave, usually it is the master cylinder leaking internally.

While it is entirely possible the problem lies within the clutch assembly itself, before removing the transmission, me, I’d replace the master cylinder one more time. It’s just possible you got a bad one the last time. I’d probably buy it directly from the Nissan dealership. If that still doesn’t fix the problem, the transmission is going to have to come out and the clutch internals inspected.

@ Dizz; Quote from the original post “Finally, once I get it working (by pumping the pedal a couple of times, if need be) it all works perfectly: firm pedal,”

Then later your reply to keith “The pedal feels normal every time, whether things are working right or not.”

Help us out here…which is correct.

Having to pump it sure sounds like either the master or slave to me. If the shop did the master first and then you did the slave…you may not have bled all the air out of the system.
Or a small leak allows it to lose pressure now and then. I had one just like it and it may go days before it would lose pressure, then the next time it would be over night. That one was a bad slave, that the tranny had to be pulled to get at it.

Yosemite

poor analogy. you replace a bad part with a good part. if the replacement part is bad you have accomplished nothing. you have a new/different bad part. same as old/bad part

Used parts that can easily be swapped out are one thing, but parts that take hours to change out are an endeavor of foolishness.

I knew a guy that spent hours removing a water pump at a junk yard to put on his daily driver. I laughed so hard when he asked the counterman if it came with a warranty.

all that to save $30 and take the gamble it not any good.

Yosemite

Thanks to everyone who has thought about this.

In reply to Yosemite’s question: the pedal always feels firm all the time. I pump it only
because after I do the system then works perfectly.

I still think the problem will be in the clutch housing, and it will be the clutch plate sticking to either the flywheel or the pressure plate. I suspect the flywheel more because if it was sticking to the pressure plate, it might take a little more effort to press the pedal down.

Does this happen when it is above freezing? If you notice that it happens only in very cold weather, below freezing, then it could be some ice forming in the clutch assembly.

Heres a couple of other things you might try. If it is safe to do this, when this first happens, shut down the engine immediately, set the parking brake good and firm and put the gear selector in either 2nd gear or reverse, whichever has the clearer path if something wrong and restart. See if the car jerks on start and if the clutch immediately breaks free. If it you get a small jerk and then the clutch breaks free, it is definitely an adhesion problem.

If it is really stuck and the parking brake is tight, it may stall the starter motor so don’t hold the key on for more than a second. If you release the parking brake and you start in gear and hold the clutch down and the car starts moving, again an adhesion issue.

There is a remote possibility that the problem could be in the throwout bearing but that could pop up anytime you are driving, and the pedal would not feel normal.

When you find it, please let us know. We would appreciate the feedback on this one. It is not something that I have seen here in the 18 years that I have been participating here, but I have seen something like this once where the clutch plate stuck to the flywheel due to rust, but that car had set up for a few months in a humid climate.

In reply to Keith’s comments, the weather here has rarely been freezing or below, and so far
the problem has not appeared in cold weather.

The first couple of times that it happened, before I learned that pumping the clutch would “fix” the problem, I would depress the clutch (in order to release the ignition lock-out) and
then start the car with it still in gear, and it would jerk forward, but as I recall keep moving.

You might try bleeding the master and slave cylinders again, but I think you have a sticking plate.

Thanks again to all who replied. It probably is a sticking plate, since I bled the system when I replaced the slave and the shop bled it again when they replaced the master, and the problem existed before, between, and after these repairs. As long as pumping the clutch pedal a few times works and the frequency of occurrence stays low I will live with it. If I have to go through replacing the clutch again I have a real decision to make, since I have to do this job outdoors!