Car keeps blowing slave cylinders out, absolutely stumped *PICS*

[TrustS13]

** RESOLUTION: Always use the provided throw-out bearing that comes with your clutch kit. The problem was that I was attempting to use an OEM Nissan TOB with my SPEC clutch kit. The OEM Nissan TOB was much smaller than the provided SPEC TOB, which caused my slave to extend to the point of blow-out each time I attempted to bleed the clutch.

Switched in the SPEC provided TOB and everything was gravy until the day I sold the motor **

Hi guys,

I am at a standstill in my build of my new hatch. The car keeps blowing out slave cylinders. I've gone through 4 AutoZone and 1 OEM that came with my S14 swap. Here are some details:

Car: 1991 240SX OEM 5 Spd car
Car did move and run, but previous owner complained he had a hard time bleeding the clutch (This was with stock OEM line, but his master cylinder wasn't adjusted right). I put in the S14 SR but it hasn't moved yet. Car is running however.
Motor: S14 SR20DET
Transmission: Stock - has new Circuit Sport pivot ball (old broke), Stock throw out bearing
Flywheel: Stock, resurfaced 0 miles
Clutch: Spec Stage 3 6 puck 0 miles
Throw Out Bearing: Stock, regreased
Input Shaft: regreasted
Pedal: Replaced pedal from my last shell
Master Cylinder: Brand new 0 miles from AutoZone (adjusted pedal properly)
Slave Cylinder: Blown 5 now
Clutch Line: Circuit Sport

I have replaced nearly every part in the clutch system as you can see. My first problem was that the pivot ball was broke on my swap. A quick call to Enjuku and I had a new circuit sport pivot ball. Installed it, threw the trans back on, and re-bled the system. It builds up pressure fine, and squirts out fluid like it should. Just went it seems to be fine, we go to bleed it 1 more time, and the slave releases no fluid or hardly a drip. When this happens, I always know it's about to blow. I close it, and my buddy starts to pump the clutch again, and then he says it looses all pedal feel. Next thing you know, fluids leaking all out of the slave. The seal on the piston in the slave has literally blown apart and the slave is now ruined.

I've gone through 5 slave cylinders, replaced the master, slave, pedal, pivot ball, and the hard line on this car.. I'm stumped and about to give up.

When I had the trans off, the shift fork didn't appear bent at all. I regreased the input shaft and TOB and put it all back together. The only thing I can think at this point is if the Circuit Sport line is causing it to blow out? Should I try a 1 man bleeder tool? The process for bleeding we are using is like you would do on any other car.

1. Pump and hold pedal to floor
2. Open bleeder, close
3. Pump and hold pedal to floor
3. Open bleeder, close.. etc.

We are getting pedal feel, we took the boot off and can see the TOB engaging the PP and the whole system working, but its like the slaves are building up too much pressure and somehow blowing out the seal. It's insane, I've NEVER had a car do this.

Either way, here are some pictures:







Any and all input would be greatly appreciated.. I'm running low on ideas. I have a local shop I could have re-create a 1 piece line, but a larger size? I don't have a OEM line, but I could try and source one (I threw mine away )

I would post this in tech, but I know it's gone missing. Thanks in advance.

Danny

[victorw210]

i have the same problem i keep blowing slaves,only difference is im running ka and have agency power clutch line

[abunai the drifter]

what kind of fluid are you using

[blueshark123]

Try using a z32 slave i think they are stronger

[BongateerZ32]

too much clutch pedal travel?

[Firestorm]

looks to me like your fork is too far away from the slave, so when you pump and pump it pops out because it runs out of travel, damaging the seal in the process?

i'm not so sure if the fork is supposed to be that far away from the slave but tbh i can't remember even though i just bolted my slave on last saturday...lol.

[TrustS13]

Just using the generic AutoZone brake fluid (DOT 3 and 4 compatible I believe). As far as the fork goes, it does have some free play but I did notice it moves pretty far back. As far as pedal travel goes, we adjusted the master cylinder properly, we matched it up to the settings up my white hatch (which was perfect.)

[doteboy]

It definitely looks like the fork is too far back! I bet the problem IS the piston moving too far out! That's the only thing that makes sense at all!

[TrustS13]

Any reason why/how the fork would be too far back? It's been re-assembled as it should be, and works fine (in terms of engaging and disengaging the PP). Still confused

[doteboy]

Not sure..? a weird throwout bearing?? My S14 sr clutch fork is quite a bit more forward than that though! Weld some tabs on your slave and move it 1/2" forward! haha Don't be scared!

[HS13KLS]

But are you putting in that copper washer with the slave? also double check the engagement on your clutch pedal. I hope you figure this odd problem out!

[nightsauce]

I'm with other people saying the fork is too far. Check your pivot ball, and the spring on the fork. Also check if the TOB sleeve is properly seated as far back as possible on the input shaft.

[TrustS13]

The copper washer is on the slave. The engagement has been triple checked and I even put in a new pedal as well. I am pretty aware the slave seems to be over extending, but how is it blowing out the seals on these slaves? Pretty crazy stuff. Also, the TOB that is on there is an OEM one (i'm pretty sure) and I noticed the SPEC TOB was much larger than the OEM one. I wonder if this plays any role in it..?

[96Turbo]

spec clutch + OEM T.O.B. = blown slave?

I would try to get another spec T.O.B. if it's larger. that should fix the travel issue

[ManoNegra]

Originally Posted by TrustS13

The copper washer is on the slave. The engagement has been triple checked and I even put in a new pedal as well. I am pretty aware the slave seems to be over extending, but how is it blowing out the seals on these slaves? Pretty crazy stuff. Also, the TOB that is on there is an OEM one (i'm pretty sure) and I noticed the SPEC TOB was much larger than the OEM one. I wonder if this plays any role in it..?

that may be it there
slave pushes on fork/tob to make contact with pressure plate
if the Spec setup requires a thicker tob but you're using an oem one
it makes sense then that the slave is over-extending and popping out

[TrustS13]

Well the cylinders inside of the slave aren't popping out.. they are building so much pressure behind them and the seals are blowing out, thus ruining them. But these are both very valid opinions and I'll probably pull the transmission and replace the throw out bearing this weekend.. le sigh

[moowee240]

DID YOU PUT THE SPLIT LOCK WASHER BACK ON WITH THE NEW PIVOT BOLT!
cant see one in the picture?
the throwout bearing wouldnt be causing this.. the spec tob diameter is larger than the stock bearing. the thickness between the two is so minimal it wont effect the system enough to mess with the slave piston travel.. did you bench bleed the master cylinder.. you could try hooking up your factory hardline..or make a new one like i did..i used stainless.

[didderson]

Spec bearing very well may be different man. Definitely install that. While you're there check to see if the fork isn't bent. I can't see that well in the picture. With non oem setups, bending the clutch fork is not uncommon.

[theredrocket]

Im having the same problem with my newly installed spec stage 1 clutch. I have gone through two slave cylinders, and am having luck so far with the third one, when i put this one on, I adjusted clutch freeplay on the pedal by turning in the rod about .25".
Now clutch does not get hard at bottom of pedal I figured there was to much travel in master cylinder rod causing to great of pressure to be applied to slave therefore forcing seals to blow just like yours.
This third slave has lasted me about 2-3 weeks now and counting keeping my fingers crossed. Getting stranded on the road with a blown slave was getting old.

[bladetech8]

Below a picture of the underside of my car for reference. You can see the slave and clutch fork are in the correct positions, my clutch works flawlessly.

I don't know what could be going on with your situation except some type of incompatibility with that clutch/pressure plate/TOB.. Maybe the clutch pedal is over extending itself on the Master if its not adjusted properly? I hope you figure this out soon man..

[Pinggg]

Clutch pivot bolt in the transmission.
i replace 3 slave coming to find out it was this bolt.
This is it broken in half vv

[brewster240]

throw out bearing/pivot ball. check em.

[TrustS13]

At the beginning of the thread I stated I first started out with a broken pivot ball as a problem, and just upgraded it to a circuit sports one (yes I did put the washer on). Hopefully I can get this sorted out soon. May look into bench bleeding it. I just don't want to buy a nice new OEM one and then blow it out again...But I will probably end up buying one.

Probably about to order a new shift fork, spring, and slave... and put on the SPEC throw out bearing (which I don't think is any wider from top to bottom, just the overall length is larger.

[TheRealSy90]

Sounds to me like you need to use the SPEC TOB.

[brewster240]

Just cause you put on a new pivot doesn't mean its the right one. This is a problem of the rod/piston over extending, not the bleeding procedure

[!Zar!]

Nismo makes an upgraded pivot ball.

[TrustS13]

I put a Circuit Sport pivot ball that is created for our cars that I'm sure many people have used..
Circuit Sports Clutch Pivot : SR20 / KA24 [ CRP-0134-GD ] - Enjuku Racing - Performance Parts and High Quality Fabrication
"Circuit Sports pivot ball was designed also to be thicker than Nismo unit."

[brewster240]

so youve never in your life bought something and recieved the wrong part by accident?

never? its not possible?

well than i would pull the trans and check to see if the fork is bent, and make sure you have the right bearing/carrier combo.

[senger]

sorry to bump an old thread, but did you ever figure this issue out? today i was diagnosing why my clutch wouldnt engage. i realized that there was a tear in the boot on the slave, so my buddy had a new slave laying around and i hooked everything up and starting the bleeding process. while bleeding the clutch the boot popped off, etc etc. basically the same exact problem that you were having, i just ordered a new slave but im wondering if this is a bigger issue. thanks in advance

[racepar1]

Originally Posted by senger

sorry to bump an old thread, but did you ever figure this issue out? today i was diagnosing why my clutch wouldnt engage. i realized that there was a tear in the boot on the slave, so my buddy had a new slave laying around and i hooked everything up and starting the bleeding process. while bleeding the clutch the boot popped off, etc etc. basically the same exact problem that you were having, i just ordered a new slave but im wondering if this is a bigger issue. thanks in advance

What clutch do you have? I had this issue with a Spec clutch that was originally intended for a CA on my KA. Luckily I caught the issue before I installed the engine and trans and shimmed the TOB a little closer to the pressure plate with a big ass c-clip. I think this may have been an issue with older SPEC clutches as the one I have is probably from 2010ish, which is about the time this thread was written. Also, do you still have the clutch dampener installed in the car? It mounts to the frame rail, has a bleeder, and is installed in the clutch line. If that fails it could hold pressure in the slave and blow the seal, but it would engage the clutch all the time as well so the car wouldn't move...