Problems Bleeding Clutch After Nismo Slave Install

[Big Zil]

Hi all

Hoping someone can assist with a clutch bleeding problem I'm having in my R33 GTR since installing a big Nismo slave cylinder. Reason for the slave replacement was that I had a clutch disengagement issue which also contributed to difficult gear selection. After checking the entire clutch system, I discovered a leak on the Nissan OEM slave and decided to upgrade as I have a heavy duty brass button clutch which was previously pretty heavy under foot.

Anyway did the replacement some weeks ago, however, have not been able to get the car on the road as the bleeding process has driven me crazy. Unfortunately when I replaced the old slave I forgot to crimp the hose and as a result pretty much emptied the Master cylinder. So I had to start pretty much from scratch as if replacing the Master.

Now I've followed the bleeding process that many describe on various threads starting from the 'dampener box' then moving on to the slave. I cannot get to a point where the clutch is coming up immediately after depressing the clutch, there is about a 1 second delay before the clutch pedal returns to normal height. I've been under the car while the wife depresses the clutch pedal and it is definitely moving the release fork much further than before with the old slave, so the improvement is definitely there.

The 2 bleeding methods I've tried are: 1) Open bleed nipple, depress clutch, close bleed nipple, pull clutch up, wait 5 seconds, repeat. 2) Pump clutch several times, depress clutch fully, open bleed nipple, close bleed nipple, pull clutch up, wait 5 seconds, repeat.

The fluid comes out of both bleeding points very strongly with no air bubbles after cracking blled nipples open under both methods. I have always maintained the fluid level in the reservoir no lower than just below the MAX level (well above MIN).

Has anyone had similar experiences, am I missing something?

[vitz_n1]

i had the same problem once. ended up being that i didn't tighten up the line into the slave cylinder enough. try going over all the lines and tightening a little bit.

Are you running the bleed hose into a jar with some fluid in it with the hose submerged?

[GeeTR]

  vitz_n1 said:

Are you running the bleed hose into a jar with some fluid in it with the hose submerged?

Yah, if your not quick enough with this nipple loosen / tighten, (for what eva reason) use some vac hose over the nipple into a bottle with some fluid in there; insures no air goes back into the line.

I try and not to though, as with a hose, you cant use a nice load distributing socket.

[Dahtone Racing]

you didnt mention it in your first post, have you bled the master as well as the slave??

[Big Zil]

  Dahtone Racing said:

you didnt mention it in your first post, have you bled the master as well as the slave??

No, can't see a bleed nipple on the Master - don't think the R33 GTR came with a bleed nipple on the Master like with a GTS-t. My car's Master is also vacuum assisted, having a large vacuum line running to the front of it from the inlet plenum.

Edited July 28, 2008 by Big Zil

[Big Zil]

  vitz_n1 said:

i had the same problem once. ended up being that i didn't tighten up the line into the slave cylinder enough. try going over all the lines and tightening a little bit.

Are you running the bleed hose into a jar with some fluid in it with the hose submerged?

I am running a clear bleed hose with a rubber connection designed to fit snuggly over the bleed nipple. I have not been submerging the end of the hose in the bottle containing the fluid though so this is something I'll give a go tonight, thanks.

[Big Zil]

  GeeTR said:

Yah, if your not quick enough with this nipple loosen / tighten, (for what eva reason) use some vac hose over the nipple into a bottle with some fluid in there; insures no air goes back into the line.

I try and not to though, as with a hose, you cant use a nice load distributing socket.

Thanks GeeTR, I'll try submerging the end of the hose in the bottle containing the fluid. I have been using a ring spanner with not too much trouble - the hose with the rubber connectiong at the end fits snuggly in the over the exposed bleed nipple.

[GeeTR]

  Big Zil said:

the hose with the rubber connectiong at the end fits snuggly in the over the exposed bleed nipple.

It does, but i find a spanner chews out the nipple pretty quick.. and when ever I'm bleeding brakes... locating a new nipple is the last thing i wanna do hah.

[our12]

Hi.

This may or not help. If you have installed a new slave cylinder you must have the bleeder at the top. If you have it at the bottom you will never bleed it as the air always goes to the top.I have seen people spend weeks and litres and litres of brake fluid trying when the bleeder is at the bottom. Hope this helps.

[Big Zil]

I have now re-bled both the 'Dampener' junction box and the slave this time submerging the end of the bleed hose in brake fluid in the bottle. First pumped the clutch about a dozen times with all bleed points closed. Wouldn't you know it, but there were still some air bubbles being expelled, particularly at the junction box. Anyway, repeated the process until no more air bubles could be seen.

Retested the clutch and the pedal feels alot better now and feels more pressured against my foot when depressing and releasing. However, the pedal will only come up immediately if I haven't depressed it all the way to the floor. If I take it all the way to the floor it sticks there for about 1 second before bouncing back up. What's going on? On the way down the pedal hits a point (about 3cm from floor) where I can feel some resistance under foot. Is it possible that the rod on the new slave has reached the maximum point of the release fork's movement? Is there some other adjustment that is required?

OR is there still some air trapped somewhere in the hydraulic system?

[Julz89]

try reverse bleeed thats what i usually do try get ur hands on a syringe and put some hose on it to fit around the nipple suck sme new brake fluid and push it up the slave nipple to the master cylinder.

[partyboy73]

  Big Zil said:

I have now re-bled both the 'Dampener' junction box and the slave this time submerging the end of the bleed hose in brake fluid in the bottle. First pumped the clutch about a dozen times with all bleed points closed. Wouldn't you know it, but there were still some air bubbles being expelled, particularly at the junction box. Anyway, repeated the process until no more air bubles could be seen.

Retested the clutch and the pedal feels alot better now and feels more pressured against my foot when depressing and releasing. However, the pedal will only come up immediately if I haven't depressed it all the way to the floor. If I take it all the way to the floor it sticks there for about 1 second before bouncing back up. What's going on? On the way down the pedal hits a point (about 3cm from floor) where I can feel some resistance under foot. Is it possible that the rod on the new slave has reached the maximum point of the release fork's movement? Is there some other adjustment that is required?

OR is there still some air trapped somewhere in the hydraulic system?

What I'm thinking is that the clutch is possibly throwing too far? Where is your friction point? What i definately know is, if you are physically pulling the clutch pedal up when bleeding, then thats where your air is coming from.

[Big Zil]

  partyboy73 said:

What I'm thinking is that the clutch is possibly throwing too far? Where is your friction point? What i definately know is, if you are physically pulling the clutch pedal up when bleeding, then thats where your air is coming from.

My friction point with the old slave was about 10cm from floor. Not sure if the new Nismo slave will alter the friction point, only aware that it lightens the clutch pedal feel by a reported 1.75 times. Physically the dimensions of the OEM and Nismo look the same, it's only that the Nismo slave is running a bigger piston internally and therefore is more powerful than the OEM one. Not sure if I should have gone for a Nismo slave instead of an OEM replacement - it's just that I needed a bit of a bionic leg with the OEM slave. In saying that though, I don't know exactly what clutch it's running. Believe it to be a brass button type clutch which another Skyline driver thought as well having had one in his car.

I stopped pulling the pedal up in the bleeding process and have been re-bleeding using the process where I let the clutch pedal come up by itself. Hose on the bleed nipple has been submerged in brake fluid. I thought I had it sussed last night but when I turned the car on, the clutch pedal felt like it wasn't hooked up to any hydraulics, pressure was as light as a feather.

One member PM'd me advising that my problems could be due to the seals inside the Master not doing their job properly after I let the fluid drain out when first attempting the slave replacement. He added that it may be possible to get them back into shape with some sharp loading (pumping the clutch pedal with all nipples closed). I did this last night and the pressure felt pretty good, definitely lighter than with the previous slave but that's what I was expecting. However, when turning the car on (and the vacuum assist coming in to play), the pedal lost all feel and even stuck to the floor for about a second before coming back up). I'm really starting to lose patience with this car, it's been a good month since I've driven her.

Not sure now if it's the Master, whether the Nismo slave is too powerful for the clutch I'm running or whether I still haven't bled the thing properly. I'm starting to think that I should just drop it off somewhere and get it looked at professionally. Just wish I could drive it to a workshop instead of going through all the dramas of getting the car towed.

[Big Zil]

Correction, friction point between 5 and 10 cm from floor with OEM slave.

[Godzilla32]

If the clutch master is bypassing fluid then you will see it leaking down the front of the clutch booster. With clutch bleeding sometimes you have to first use a sucker to pull the fluid through and then give it a pressure bleed.

By having a larger slave and continuing to use the stock master it won't have the same hydraulic ratio. Are the Nismo big slaves mean't to be used with the stock master? I thought the smaller original master wouldnt have the capacity to efficently fill the nismo slave.

When you feel you have an ok pedal you need to check under the car how much slave travel you are actually getting.

[Big Zil]

  Godzilla32 said:

If the clutch master is bypassing fluid then you will see it leaking down the front of the clutch booster. With clutch bleeding sometimes you have to first use a sucker to pull the fluid through and then give it a pressure bleed.

By having a larger slave and continuing to use the stock master it won't have the same hydraulic ratio. Are the Nismo big slaves mean't to be used with the stock master? I thought the smaller original master wouldnt have the capacity to efficently fill the nismo slave.

When you feel you have an ok pedal you need to check under the car how much slave travel you are actually getting.

Godzilla32, thanks for your input. There are no leaks anywhere on the entire clutch hydraulic system from top of Master all the way down to slave. That is one of the first things I checked. The fluid is flowing quite strongly from both the junction box bleed nipple as well as the slave bleed nipple during the bleeding process so I have no doubts that the fluid in the lines are at or near full capacity. What are the exact steps when using a sucker followed by a pressure bleed?

The Nismo slave definitely has a bigger displacement than the OEM one but I wouldn't have thought that it was that significant over the OEM one, I know that some members are successfully running Nismo slaves with stock Master cylinders, some however are running modified clutch lines that bypass the 'junction' box.

Don't think there is a capacity issue with the OEM Master/Nismo slave combo as I've observed the movement under the vehicle. The slave is definitely getting good strong movement against the release fork, about 2 cm and actually strecthing the rubber boot around the release fork a few mm so I know that it's at it's maximum movement. I observed the movement on my old slave before replacement and I was barely getting 1cm of forward motion. As I said I have an o.k. pedal feel and movement with the car off but when I start it up and operate the clutch I hardly get any pedal pressure, so it's like the vacuum assist lightens the pedal feel so much it's as light as a feather but it also ends up sticking to the floor when the car is on. I have not observed the slave movement when the car is on but I'll have a look tonight and hope that the wife doesn't do something silly and drives off the blocks the car is sitting on.

[Big Zil]

Just an update on my progress with this issue. Following some really helpful advice that was PM'd to me by a SAU member, it turned out that my issue was related to an internal seal problem which all started when I inadvertently let the Master cylinder reservoir drain completely. The advice that I was given was to turn the car on (and therefore activate the vacuum assist) and then aggressively pump the pedal with all bleed nipples closed. I first topped up the reservoir passed the MAX point which would later prove a wise decision. Anyway pumped the clutch pedal by hand for what must have been at least 30 times before noticing some improvement in the pedal pressure. Upon then checking the reservoir, to my complete amazement the fluid level had dropped a few mm below the MIN level so lucky I topped up the reservoir at the start, not sure why I did it but lucky I did as I could have ended up sucking more air into the hydraulic system. I wasn't expecting this particularly with all the bleed nipples closed. Anyway, I re-bled to ensure that there was no air in the system and noticed that after every single bleed the fluid level was falling muck lower than before so when the clutch pedal was being released the suction in the Master was much stronger.

The clutch is now all good and the slave movement is more pronounced than before even though I initially thought that the slave was at maximum movement, it wasn't. It is also alot quicker in it's movement against the clutch release fork. Gear selection is alot smoother than before where sometimes I was fighting to get the car into 1st or getting the clutch to disengage completely when coming to an intersection or traffic lights. I re-tested the clutch pedal feel with the car running as well and is significantly better and does not stick at all. Definitely lighter than before though but I was always expecting that with the bigger Nismo slave.

I have yet to road test the car as I finished up quite late last night but should test tonight after work. Let everyone know the final outcome. Thanks for all the advice -these forums have helped me out yet again.

Edited August 7, 2008 by Big Zil

[Big Zil]

Just a final update on this as I have now road tested the car. Clutch disengaging properly now, gear changes (particularly when getting into 1st at standstill) are so much smoother now and the car has become a pleasure to drive (particularly in stop/start traffic) again. Thanks to everyone's input, I've learnt alot about hydraulics and the pitfalls in maintaining these systems.

[R33GTRKid]

Wow this is exactly the same problem I am having following ?-X*&^% installing a twin HKS Max.

The engagement point was right at the top of the travel and the pedal felt very spongy. It felt like it badly needed bleeding so I took it back to ?-X*&^% who also changed all brake fluid as well at the same time in an effort to fix my spongy brakes following compliance. All they did with the clutch was lower the pedal travel, so now the engagement point is still at the top of the travel, the pedal just comes up less distance from the floor (I mean honestly WTFFFF).

They said the brakes will not get any better (I mean the abs does not even kick in on a set of GTR brembos with less than 60 k on em???) and that I need to replace brake booster, lines, discs and pads????)

Well after that I am off to another workshop in Welshpool tomorrow morning to hopefully have sorted spongy clutch and brakes sorted once and for all.

Fingers crossed!