Clutch slips in heat!!!! Need help quick!

[Chainsmokerjoe14]

Okay so I recently purchased a 91 240sx se coupe. It ran perfect when me and a friend who is a master tech, he just hasn't had time too look at it, and I feel like a tool asking him for car help. So when I purhased car, he showed me paperwork of the engine he purchased that he put in himself, 114k miles on engine, so when he put it in he put a stage 2 clutchmasters clutch, and a lightweight clutch I believe he said 12 lbs? He also said since install of everything he put approx 500miles on It and toldme too put a other 500 to break it In, only time car ever hits over 3k is sometimes in first, but then I baby it into 2nd so I dont jab it.well, when purchased it was cold outside and cotinued too be cold for first week. After that it was exceptionally hot outside, and when going through traffic I noticed that it would slip when I shifted and once I revved engine it would sometimes catch sometimes not. He swapped mc day before purhase, from his experience with cars I assume he did everything right, everything on this car was flawless. But this is what I do not get, it works fine at night when it's cold, or when it starts slipping bad in traffic I pull over shut off car, pump clutch approx 10+ times and made a woodenrod that hold clutch too floor while I bleed it and it works till next time I have to go through traffic, and I wanna figure this out before I leave in 5 days for Florida and I have to drive! I've read other posts. I'm checking box too see if it's been bypassed already. If not I have a steel braided line brand new available too me, because my friend ordered 2. And told me I could buy it, he said it stiffens up clutch, or something. Also when I touch boot on slave and move it like compressed air shoots out. Not alot, but enough too hear it. Also it's weird clutch will be stiff then soft then stiff again. I don't know what too do, I just no at night it shifts perfect like i just bought a brand new car. But I'm getting scared I'm going too ruin clutch if prob isn't resolved soon!
Ty for help in advance! And sorry if I have typing errors using my itouch and it's a pita too type on sometimes!

[Dire91]

Trying bleeding the clutch, there may be an air bubble floating around or something because I hear bleeding the KA is semi tricky. I have heard stories where the hot weather heats up the clutch fluid so much that it looses its functionality and the clutch starts to slip, that could be it. I don't know how hot it gets where you live but I would check the fluid and ask your friend what he used.

[speedeast]

When in doubt bleed again. What I would do is start the process over from step one to ensure you cover all of your bases. Take the Clutch Master Cylinder out leaving the clutch line fastened high not to lose any fluid. Bench bleed the CMC, then reinstall it and bleed the whole system at the bleeder valve on the Slave Cylinder. It is definitely best to bleed it with a friend, but if you can find two, the process goes much faster. One on the clutch pedal, one on the bleeder valve (usually my position of choice), and one keeping the fluid level perfect. Just a heads up in case you didn't know, DOT 3 or 4 brake fluid is what you need, don't waste your time searching for something labeled clutch fluid.

Good luck.

[Chainsmokerjoe14]

See I've been using clutch fluid cuz alot of people tell me 240sx are the same as any car, they also told me gl-5 was fine in my transmission, thankfully I didn't listen and am putting gl-4 in today, btw I do normally bleed with 2 ppl just sometimes that's not an option. The mc was bench bled, also, I just really think I need somin that can keep from getting too hot. Is that dampener really that much of a cause of problems? So brakefluid is fine though? Cuz I'm sure that can handle higher temps then clutch fluid.
lol. But I guess Ima try to bypass dampener bleed it again. And if that doesn't work, get new slave. And there really can't be much more beyond that.

[speedeast]

Brake fluid is more than fine.

[gumby74]

If you have already bled the clutch system in an appropriate matter and the clutch still slips, you need to adjust the m/c again.

Lay down on the driver side floor board and look up just behind the clutch pedal. You will see the m/c rod connected to the back of the pedal. Remove the cotter pin and push out the clevis pin. There will be a turn buckle with a jam nut that needs be loosened. Turn the rod 1/2 turn and re-attach the rod to the pedal. Go for a drive and see what happens. Adjust the rod only 1/2 turn at a time. You want to turn counter clockwise, or is it clockwise? um.... make the rod longer, so I guess that would be counter clockwise.

Also at some point fork out for the long braided clutch line that eliminates the annoying dampener box. You will not regret this modification as it a) makes the clutch pedal firmer and b) makes it sooooooooo much easier to bleed the system. And finally buy one of those $3 one man brake bleeders they sell at most parts stores.

[speedeast]

you need to adjust the m/c again.

That slipped my mind! That's probably your problem. It just means you're not fully disengaging when you press the clutch. Keep us posted on what you find!

[Chainsmokerjoe14]

Hmm, I will try the mc rod thing 2morro it's dark out now, but I have a feeling that te dampener is the culprit, I was under there, and the bleeder is practicially stripped, so I'm sure there is a thread on how to bypass that? If that doesn't fix it, then the pedal adjustment is next, it'd just weird, when it's cold it disengages perfect. Everytime, just when I am driving in heat and shifting alot, when it's impossible to almost not ride the clutch. Is when it slips. I will for sure keep you posted, but I will say after swapping in the API gl-4 the shifting is 100x smoother, I doubt it's gonna help for the clutch tho :/

[speedeast]

The symptoms fit for the pedal. When it's cold, it gets better grip, but it is barely hanging on. The warmer it gets in there, the less grip it has. If you think it's the slave cylinder... those are like $13 at the auto parts store. But I would try the pedal first.

[Chainsmokerjoe14]

hmmm... well, ima get the braided line like 2morro, and i may as well adjust the mc while im at it.. what in the world is cotter pin etc... like im sure there is a thread for it, but searching on an itouch is a pita so if any1 can give me a simplified way to do it. ill be able to do it myself... ugh why can everything be like car audio. labeled hahaha

[speedeast]

Here is a picture of the clutch master cylinder:



If you notice on the far right you see the fork that attaches to the pedal. It is on a piece of threaded rod. If you twist it one way it will get slightly shorter before it won't install. If you twist it the other way, it will get a little longer before it threads right off the end.

Your goal is to thread it out little by little to make the bolt longer. By doing this, you are giving the cmc plunger a more suitable travel distance inside of the cmc. This will push more fluid to open the slave cylinder just that teeny bit more that you need to better disengage the clutch.

The holes on the end of the fork accommodate a little pin that holds the fork to the pedal; the pin is held in by a cotter pin:


^ I don't believe this is the same type of cotter pin, but if you get one of these it will make the process much easier/faster as they are easier to install/remove.

Good luck.

[Chainsmokerjoe14]

how far should it go. like i went under to adjust it and the rod was almost rdy too fall out. like 2 threads away from not even being in there. like im sure its gonna new quite afew more turns then like 1 full turn. any recomendations. because i havent noticed a diff lol ive done 3 turns so far, only diff i kno is when the pedal is catchin lol. but it hasnt been hot so i dont know when its gonna slipp. but i def am glad i looked at that before i leave lol

[speedeast]

it doesn't take much. let it get hot and see how it works if it's better. if the slave cylinder is the problem, like I said, they're like $13 and usually in stock at an local auto parts store.

[liquid_cool]

When in doubt bleed again. What I would do is start the process over from step one to ensure you cover all of your bases. Take the Clutch Master Cylinder out leaving the clutch line fastened high not to lose any fluid. Bench bleed the CMC, then reinstall it and bleed the whole system at the bleeder valve on the Slave Cylinder. It is definitely best to bleed it with a friend, but if you can find two, the process goes much faster. One on the clutch pedal, one on the bleeder valve (usually my position of choice), and one keeping the fluid level perfect. Just a heads up in case you didn't know, DOT 3 or 4 brake fluid is what you need, don't waste your time searching for something labeled clutch fluid.

Good luck.

words of wisdom here..some info he posted you might want to consider again!..like your choice in fluids!..
dot3 is a standard fluid up to a certain temp befor it flash boils...after that comes dot 4..i can withstand higher temps and still absorb water like dot 3 does...then there is dot5..rarly used couse IT DOES NOT absorb water..last but not least..a verry high temp racing fluid...dot 5.5..this does absorb some water..and can withstand extreem temps..this may allso be known as dot 4.5 to some shops...

bleeding...bench bleeding the master is allways a good idea..another trick i like to use to get air out is to reverse bleed using a verry large seringe..like the ones for rabie shots..insted of a needle..i use medical hose and fill that sucker up with fluid...starting with the lowest point on the system..i then force the fluid throu the system ..this will push any air out....best to do this with 2 people as the 2nd person needs to watch the disconnected line by the master to say when and re-connect it...fastes way to bleed a system in my book..anyways..good luck man..ps....some clutch set ups may need upto 2000 miles to fully break in allso..

[Chainsmokerjoe14]

well, i gotta wonder now, i see a thread on bypassing dampener by bending hard lines.. now could i not disconnect the line coming from MC get a braided clutch line. and hook that straight into slave and remove rubber, killing too birds in one stone? because that seems like simplest way to do it without having to worry about kinking the hardlines, bypassing dampener, and getting rid of rubber hose. i will say this though, i made a 700 mile trip just fine, hasnt slipped really since i adjusted mc accept twice, and that was cuz of 2 idiots that almost tboned me and i had 2 haul a** outta way and it didnt wanna catch 2nd. but i think once i bypass dampener i bet it will be done. because now it doesnt do it when hot just randomly. so im guessing its an ait bubble.

[omegahunterbass]

This has helped me get some ideas to fix a 240 i am looking at. The owner mentioned the clutch fork, but from reading this and a few other thread, I am certain that may not even be an issue. At least with this thread i have some extra things to try to fix it. I just need to find out how to install a new clutch fork, should it come down to that... searched and didnt find any threads on that... If there are any, please feel free to link them.. I would appreciate it...

[compactfean]

Clutch forks are an internal component of the transmission and the trans must be taken apart to do so. The best ”write up” is the fsm found here at the top of the technical forum.