Clutch Hydraulics

[PapaSmurf2k3]

OK, heres the problem. my clutch fluid is turning black, and my pedal will build up pressure, and the engagement point will move all over the place (starts near floor, and then moves up high), after it is at its highest point for about 20 minutes, i will go to shift, and it will have almost no pressure at all, and the engagement point will be right on the floor, and i baisically have to force the transmission to go into gear. I have adjusted the pushrod many times, as well as the freeplay screw, both seem to have no effect on this pattern.Heres what i have:Master Cylinder less than a week oldSlave cylinder less than a week oldDOT 4 brake fluidDual friction clutch and pressure plate (although that shouldnt matter because its a hydraulic problem)system has been fully bled many timesI replaced my master and slave cylinder about a week ago because my slave cylinder began to leak, and i also noticed that the fluid was black. before i had done that, i replaced the master and slave about 7 months before.while it does this pattern of moving the engagement point, and then loosing all pressure, the fluid level stays constant, i havent lost any fluid since the master and slave have been changed. Im starting to get pissed. What is up?

[PapaSmurf2k3]

Oh yeah, and it appears to have something to do with heat, and how long the car has been running and whatnot. when it first starts up and its cold, its low, then as it warms up and i drive around (not exactly proportional to the heat of the motor, the clutch is somewhat slower if you know what i mean) the clutch will move up, and then after ive been driving for about a half hour to 45 minutes, it will do that thing where it looses all pressure.

[NISTECH]

if the hydrolics were the problem it would be consistantly bad not fluctuate with one exception. The master cyl. is the exception. If it were to have a fluid by pass problem. You said its new so its most likely not the problem. From your description especially the info you provided in your second post I am thinking pressure plate problem or fork alignment problem. If it were fork alignment there would be noise associated with it.

[yellow_jacket]

If he didn't get all of the air bled out he would have this problem though. If I understand him correctly, he pumps the clutch to get a good pedal, then drives and it gradually goes bad again due to lack of pumping. I would try bleeding it again, maybe even taking out the box.

[PapaSmurf2k3]

yellowjacket- do you have directions, and what parts are needed to take that box out? i have a feeling that that is behind all this, just because it is the only thing that i havent replaced, and it must be hydraulic because everything els is mechanical, and mechanical things dont just fluctuate like that, they just break. also, why would the fluid be turning black? any help is greatly aprreciated.

[Z3Px]

I just rebuilt my clutch master cylinder this weekend and bleed it out again, it works like a dream now. I was having most problems with the hydrolic fuild leaking and the clutch randomly going out, i would bestly try to blead the clutch again

[Structure240sx]

u can bypass that damper box, if thats what u talking about, with a line that takamotorsports sells. i jsut got mine a couple days ago but havent finish my car yet. buudweizzer on nico loves it. it would be good to get rid of another possible problem while upgrading. it cost me $45 shipped and arrived in like 4 or 5 days

[PapaSmurf2k3]

$45! for a line? dayum, is it really worth it? let me know how it works out and stuff when you do it.

[yellow_jacket]

you can probably make your own for $5.

The clutch fluid turns black from the seals going.

[PapaSmurf2k3]

the seals are already going? the damn thing is like a week old. anyway, do you know what this line is composed of, so i can make my own for $5?

[Structure240sx]

its a steel braided line u just need to find out the right fittings for it i guess. its worth not having to go through the trouble to me

[sgp180sx]

u can bypass that damper box, if thats what u talking about, with a line that takamotorsports sells. i jsut got mine a couple days ago but havent finish my car yet. buudweizzer on nico loves it. it would be good to get rid of another possible problem while upgrading. it cost me $45 shipped and arrived in like 4 or 5 days

the nismo stainless steal line also bypasses that doesnt it. The nismo one is like ****ing 80bucks though.

[180fan]

yes the nismo one bypasses the clutch damper. the takamotorsports one is very well made. I too have one. cost me 47 and some odd cents for tax and what not since I live in CA.

to build your own, you'd need to find the proper fittings (standard hydraulic line measurements aka pitch and thread size for nissans) and the steel lines that are build for hydraulics then you'd need to assemble it. Not worth the time to go cheapo on the clutch line. Besides, the one from takamotorsports has a tube that goes around the fittings and on the steel lines to prevent crap from getting in there to potentially damage the steel braids.

[sgp180sx]

the takamotorsports one is the 35buck one that says remove loop and damper right?

[180fan]

yeah that's the one. it's not really just 35, there's another 10 bucks for shipping and if you're in CA, then you pay more cuz of tax.

[stutt944]

i too am going through this problem as we speak. took the car over to a nice shop this afternoon, turns out the clutch pedal adustment was off by like 7 or 8 threads. they put it back to having just 2mm free play. now (and for the first time ever) the clutch pedal feels "springier" or stiffer, i guess you'd say. the engagement is only at the top 10-15 percent of pedal travel. and the clutch is starting to slip. they said it may be the master cyl, the slave cyl, or both at once. im not very good at hydraulics work. so bad, in fact, that i've had brakes fail completely on me because there's something i just dont grasp about hydraulics. i dunno. anyways, any advice? there's no air in the lines, and the clutch is only 12/13K miles old. i'm not sure what to do. start replacing parts?? why does the clutch slip? i dont get it. the only thing on a damn car i can't figure out is a clutch.

[stutt944]

damn this is frustrating. explain it all to me ONE MORE TIME. i've read about the clutch master and slave cylinders so many times, but i still dont understand what they do exactly, and their relation to each other.

[sgp180sx]

yeah that's the one. it's not really just 35, there's another 10 bucks for shipping and if you're in CA, then you pay more cuz of tax.

thanks, yeah im in ****ty cornville nebraska so i dont have to pay tax.

[PapaSmurf2k3]

Slutt (hehe)- Baisically, the master cylinder is a pump. what it does is pump fluid into a line. Since brake fluid does not compress, it reaches the slave cylinder and pushes out on a diaphram type thing that is connected to a rod, which pushes out onto the fork and throwout bearing and whatnot. When the pedal is released, the fluid returns to the master cylinder, bringing the rod on the slave cylinder back in, which brings the fork and throwout bearing with it. Good enough explanation? somebody correct me if im wrong, i might have the fork/throwout thing a bit mixed up.

[PapaSmurf2k3]

What you can do (slut) is take your master cylinder out (move the seat back, follow the clutch pedal to the rod and fork type thing and pull off the clip that holds the pin onto the fork, then pull the pin out. Now open the hood and unbolt the master cylinder (obviously, drivers side of firewall, kinda behind the strut tower) for the one closest to the brake booster, youll probably need 2 extensions. once you get it out, tighten the fork in a couple of threads, and reinstall the master cylinder and take it out for a spin and see what is up).

[PapaSmurf2k3]

whoops, read that wrong, stutt, oh well, slutt is good too. sorry mods.

[stutt944]

its been mistaken before. i just tell them "yes, i get as much action as i possibly can."

great explanation. i finally get this. i hate that where something is right in front of you and you just dont grasp it. the lay-person's explanation was spot-on.

OK. so if the slave cyl is going out/not sealing, your fork may not be manipulated the way it was intended to be. less movement, etc. and if the master cyl is messin up, you're just not really getting anything done. same thing happens (in a simplified way) when air is in there.

OK so...why was my clutch pedal (or master cyl threaded rod) adjustment screwed in like 7 or 8 threads? there should be only 1-3mm of play, correct? why on earth would anyone adjust it so radically? i think the guy who put in my clutch had it out for me. honest. he always tried to overcharge, too. prick.

what correllation does a slipping clutch have? i understand that after 6 7 8 9 10 hours of constant driving, some hard driving, you're going to have massive heat transfer resulting in a weakend pressure plate or disc or both. but why, after only 5 minutes once everything gets lubed up, would the clutch slip when engaging 1st gear? not quickly, by any means. it just slips and shakes. should i check on the fluid? maybe a higher quality fluid as well as a better line or something? probably wouldn't hurt to rebuild/replace slave cyl, eh? SORRY FOR THE EPIC I JUST HAD AN EPIPHANY TO END ALL. i need a cigarette.

[stutt944]

i suppose 98% shot transmission/motor mounts would exaggerate this problem, no? damn i hate when things need replacing.

[180fan]

you could always have a friend depress the clutch pedal while you're under the car to see if the rod is coming out of the slave cylinder.

[stutt944]

a what? kiddding ...yeah today is the day.

[PapaSmurf2k3]

new developments- it seems as though after my clutch builds up pressure, it will keep its engagement point at the very very top, until i try to adjust the freeplay screw so it has some freeplay, in which case it dumps the pressure and engages on the floor. any thoughts?

[O0ooAJoo0O]

yeah im having the same damn problem with the hydraulics. ive got a new master cylinder, which ive found to be defective and a new slave cyclinder(still good). i also bled the line like 3 times. there is NO air in it. (i used an entire bottle of DOT4 abs fluid) i put the old master cylinder back on, because i found that the new one wouldnt hold pressure. the original still does. my probelm is that when i pump the clutch REALLY fast for a few mins, it will build pressure and hold. but as soon as i slow down or stop, it looses all pressure and the pin(on the slave) goes back into the cylinder. its buggin me out. i know there is no air in the line, the slave works and the master works, but i cant keep pressure. any help for me would be great, too

-AJ

[stutt944]

well today my clutch "went out" completely. all slipping when in gear. would not move itself anymore. so i waited until 2:30 am when it was coldest, everything had just enough tension to get it to the shop. the clutch has only been in for 16K miles. my problem could still be any number of things. perhaps the clutch was put in backwards? it could be all elements are FUBAR'd, it could just be an adjustment issue. whichever way, the car barely moves, but the slave pushes the fork a good ways (inch and a half, two inches) so i have no idea. im pissed. im broke. this always happens to me. any suggestions? anyone??

[PapaSmurf2k3]

yeah, pull the master cylinder and move the fork on the rod in a couple of threads. as far as my demons go, yesterday i was driving around and the clutch went sky high again so i said "alright thats it" and went to my friends house while he wasnt there and swapped my master cylinder with my old one (i kept it in the trunk specifically for this reason). After bleeding the piss out of it, and trying just about every combination of rod throw (fork/thread adjustment on the master), the pedal would go to the floor and come back up (meaning it had pressure) but it was no where near as hard as it was before. So, i swapped in the new master cylinder again (trying to cut my losses, just so i could drive it again) and now i have the same problem. I can see the slave moving about 3/4 of an inch to an inch if i have someone press the pedal while im under the car, but it still wont go into gear, which leads me to beleive that something "FUBAR'd" inside my transmission, and the fork and throwout bearking arent pushing anything anymore, which would require very little effort to move the slave, and thats why it is very easy. What im going to do now? besides drive my moms car for a little while, i do not know.

[stutt944]

**** we need some other people to read all this and help out. in a bad way.