Hey guys, so here’s kind of a run down of what’s goin on. Had my car apart for a build, upgraded to a concentric hydraulic clutch, and I cannot get it to bleed appropriately no matter what I do. Retained stock master cylinder, slave is replaced with the concentric clutch, no leaks detected inside the cabin, engine bay or bell housing. I’ve bled it multiple times using their instructions, I’ve bled it multiple times using alternative instructions from their website, I’ve done the hose in a bottle filled with fluid trick, and I’ve repeated these things multiple times going in excess of the amount of times it recommends. I do get fluid through the bleeder valve, I’ve ran close to a whole bottle of brake fluid through it, the pedal does return to top position without assistance but there almost no pressure when depressing the pedal. The only thing I haven’t tried is one of the vacuum bleeders. I’m curious as to if my master cylinder isn’t bad (previously functioning fine). Anyone have any ideas?

 

Edit

 

Don't have a good answer for you, but curious as to why that concentric slave cylinder appears to have 2 orange hydraulic lines showing up in the picture? Where is that 2nd line supposed to go? Never messed with one of those before, but not understanding why any clutch slave cylinder would need to have a 2nd line attached to it. I suppose that if 2 lines are required, it's possible that reversing the plumbing connections to the ports on the slave would cause problems.

 

I thought the same thing when I opened it up lol but bottom line is from the master and top line has the bleeder valve connected to it and is accessible behind the bell housing

 

Several thoughts about your clutch slave:
1. The bleed line I assume is the top one. It goes up and then down. That may trap air in the "up" portion. One should attempt to have the bleed line always going up.
2. Is the bleed port at the absolute top of the fluid volume in the slave? If not, that can cause bleeding issues. Also, in the unlikely case that the lines are reversed, bleeding will obviously not be possible.
3. It looks like you have Teflon-lined SS braided hose. Because of the orange cover, I can't really be certain. If so, that part is OK. If the hose is not stiff enough, hose expansion may make the pedal soft.
4. Does the slave have more pressure area than the original slave? If so, you may not be getting enough fluid displacement from the MC to press the clutch spring far enough to disengage the clutch.
5. What is the free travel from slave bottomed out until the TO brg contacts the spring? If that's too much you won't be able to disengage the clutch before the slave goes too far and you will have a soft pedal or leakage due to over-extending the slave.
6. Does the slave have enough designed-in travel to disengage your clutch?
7. In the line from the MC, if there are any raised areas, those can trap air.

 

1. it is the top line, there were….adequate at best…instructions for it lol so I went with the theory air rises and placed the bleeder on top. I have not tried bleeding it with the hose up though so that is a thought! I will try that when I get off of work.

2. I’m assuming it is…there’s only two ways to orient the slave and that’s with the lines facing the left or the right side.

3. Yes it is Teflon SS lines. All are brand new and came with the kit. I see it as an unlikely source of error but anything is possible.

4. Very valid point. I am unsure of that answer. The kit was designed specifically for the FD trans and converting the TO bearing style. So I would assume they took that into consideration.

5/6. I’m unsure if the free travel distance. I haven’t been able to build enough pressure for that to occur yet. The clutch forks are only a couple inches away from the TO bearing, pics from this company show it extending much further out than necessary for my application. So I’m assuming the distance is ok.

7. There are no raised areas, it’s a hardline until it goes down into the bell housing. I might have a pic, I’ll attach it if I do.

I know I’m “assuming” a lot at this time, I appreciate your help with the trouble shooting! I have a few things I can check later.

 

Ahhh, now that makes sense as it would be impossible to bleed otherwise unless you had a big enough access hole in the bell housing to get in there & bleed it. Seems to me that routing of that bleed line could be critical - I think the line should be higher than the bleed port height at all points along its length to ensure air can escape when you bleed it. Using a pressure bleeder (e.g., Motive) might make the job easier too.

 

Perhaps, try a Mityvac. I went through ~2 quarts bleeding my T-56 through a remote bleeder with very little air bubbles. Still had a very soft pedal. Eventually used a Mityvac at my clutch master( separate from brake) and was able to get a hard pedal.

 

I agree that a pressure or vacuum bleeder should be able to bleed OK even if the line orientations are not optimum. Getting some continuous fluid velocity during bleeding can overcome raised areas in the lines that trap air. They will not always, however, bleed a trapped slave volume if the bleed port is not at its very top.

 

Awesome thanks guys, I tried bleeding with the bleeder above instead of below, got some air out, The bottom quarter of the pedal is stiffer now, and I can see the TO bearing engage but not enough to disengage clutch. I think the vac is the next step.

 

what do you mean when you say you used it at the clutch master? Where did you connect it specifically?

 

I have a separate clutch master cylinder, that is...not connected to the brake master cylinder.

I placed one of the Mityvac tapered nozzles in the center of the master ( below the reservoir) so it would not suck fluid from the reservoir. I actually cut the tip off so the taper would fit securely in the master's opening.

 

Here's a step by step procedure in this link

https://www.norotors.com/index.php?topic=17322.45

 

Ah makes sense! I may be able to rig something up to work that way. And when you guys say mityvac are you talking about the harbor freight one that’s about 50$?

 

This one is similar to what I have. Mine is an older model.

 

So I bought the mityvac, and what I did was depress the clutch and hooked the vac to the bleeder and at about 20-23 mmhg and it did pull fluid with the clutch depressed, is that normal? I was just worried about something being wrong with the slave. Also after I did that until I got no more air bubbles, I had some pressure in the clutch but not enough to disengage the clutch. I was thinking about renting a pressure bleeder for the next step

 

Not sure about that method. I put the vacuum line inside of the reservoir not on the bleeder. Do you have a separate reservoir for your clutch or is the reservoir shared with the brake master?

using pressure seems like a good approach.

 

btw. I'm not drawing fluid when the tube is inserted in the reservoir

 

I saw a couple videos with people doing that and like you said, not drawing fluid, but more so air bubbles. Unfortunately it shares the same reservoir as the brake master, and I couldn’t really figure out a way to do that.

 

i think having the shared reservoir complicates the problem. an alternate approach would be to disconnect the brake lines to the master and plug the master, then use the master reservoir to either vacuum or pressure bleed the clutch system. Or disconnect the clutch line from the brake master and pressure bleed from that line or using your bleeder valve.

 

I think a vacuum bleeder attached to the bleed hose would do the trick. You will have to assure that the clutch side of the MC reservoir never runs dry.

 

the clutch aspect of the reservoir is the top 25% of the reservoir (just and fyi for anyone who might be dealing with the same) I’ve ran so much fluid through it using the bleeder and still no luck…I’ve been trying to borrow a pressure bleeder with no luck so I may have to bite the bullet and purchase one. I have movement out of the throwout bearing, it’s just not enough to disengage

 

So I think I have it bled as much as possible. Only getting very small air bubbles at this point. The clutch has some free play at the up position, maybe about 10% of the stroke? (Still won’t fully disengage) Would adjusting the clutch to alleviate the play at the top fix this problem?

 

Any bubbles, even small ones, is usually indicative of incomplete bleeding. Unless air is getting in at the bleed fitting (common with vacuum bleeding), there is air left in the system

Does the pedal feel "firm" when it does engage? If not you may still have an air entrapment issue. Removing free-play may help, but it may not fix the underlying issue.

 

I hooked up directly to the flare because I was getting so much extra air seeping through the nipple threads. They very small, like “micro bubbles” I guess? It does feel firm once it hit the engagement point but gets progressively more firm towards the bottom which makes me think I may be compressing air in the line.