Update: Evoms doesn't have that braided line. They are sending me their line instead.

 

So, I was just thinking about this thread, and realized I should take a look at my clutch fluid to see if it still looked alright. Short answer: it doesn't. The reservoir is full of white sludge and black specs and flakes. The clutch still seems to be operating ok, so I assume this is the inside of either (hopefully) just the reservoir hose, or possibly both that and the hydraulic hose to the slave. Here's how it looked:



I sucked all that out, cleaned out the reservoir and refilled, then pumped the clutch a couple times and a bunch more white floaties and some more black flakes came back in.

So, I guess I need to find a replacement reservoir hose that can handle DOT 4, and then thoroughly flush the fluid and see if this comes back.

Can't believe BBI is still selling these things years later without any acknowledgement of the fact that it will fail unless all the OEM parts designed for Pentosin are replaced. Hopefully it's just the hose(s) and not the master cylinder seals that can't handle brake fluid.

Edit: one interesting thing: I just spoke with Sam at EVOMS and he mentioned that they don't replace the reservoir hose for their GT2 kit and haven't had problems with it. He also said that that kind of white sludge comes from pentosin and brake fluid mixing.

What I can't understand is how there could possibly be brake fluid in the system still. When we first installed the BBI slave we thoroughly flushed the system. Both the rubber hoses swelled and disintegrated. We assumed it was from pentosin contamination, so we replaced the hoses and flushed it again. The new hoses did the same thing. So that time we replaced the master cyclinder, replaced the hydraulic hose with the braided one, replaced the reservoir hose with a new stock one, and flushed again. And yet somehow apparently there's still contamination. WTF

 

So.. can someone recommend an appropriate brake fluid hose that could be worked in there, as well as a pressure bleeder? I've only ever done gravity bleeds before, but I'm guessing I'll need more than that to work all this sludge through.

 

I think my tech used Porsche brake fluid hoses from a GT4. He cut it to length.

Sorry I don’t have the part number.

 

Anything rated for pentosine (CHF 11S) will definitely handle DOT4 as the former is more corrosive. Problem is that old hoses have tiny cracks in their ID that may retain some Pentosine and cause problems. I’ve had the slave in my car since 2016, only issue was with the slave hose about a year in, and it was an en crimp failure rather than rubber swelling.

Only other issue I have with the slave is after some spirited/track-like use the clutch pedal feels a bit vague with fine vibrations that goes away by itself, the working theory is that’s due to the brake fluid we used. Plan is to try Motul 660 next and see if it makes any difference.

 

Thing is, I've flushed the system repeatedly, replaced the rubber hoses multiple times, and even replaced the master cylinder. The problem keeps returning. So it couldn't be just that the original hoses are retaining Pentosin, because they're long gone. I can't see how there could still be Pentosin hiding anywhere. Unless even a miniscule trace amount is enough. IE on the first run only the slave was replaced and everything else flushed. So maybe at that point with the rubber hose cracks and whatever it was like 0.1% pentosin still. So then when I flushed everything again and replaced the hoses and the master, a tiny amount of that 0.1% pentosin mix was still trapped in the bbi slave (the only part not changed) and so now I've got, like, 0.0001% pentosin in the brake fluid?

But I mean, really? If it's really that sensitive, ISTM the only way to properly install one of these BBI slaves would be to remove the reservoir, cap, hoses, master and slave cylinder, directly flush the hard lines thoroughly with DOT4, and then install the new BBI slave with a new set of hoses, reservoir, and master. Then maybe you'd avoid these issues.

 

Could it maybe then be a defect in the unit you have?! As it sure sounds weird.... the slave retains the original pentosine lines maybe an internal leak/crack? Just a wild guess ...

Maybe wise to speak with BBi about this as I assure you your experience is not normal.

Good luck

 

Looks like evoms had something made up. What they sent me looks nice.

 

I did speak to them back in 2017 when I originally had these problems. They said they hadn't heard of others having the same issue as long as the pentosin was flushed from the system. However there are multiple others in this thread and others like it who've run into exactly the same thing, and like me have had their hoses fail multiple times. So while I believe that some people don't seem to have issues, this does appear to be a relatively common problem.

My understanding is that while the BBi slave has a pass-through for the power steering system, it's completely separate, so the actual metal body of the thing would have to be compromised for them to mix; I can't imagine how that would happen. I suppose it's possible though.

At least now I can see clear signs of the mixing right in the reservoir, rather than having to get it out on the track to exhibit problems. So I think at this point I'll just replace that reservoir hose, ideally with something specifically designed for DOT 4*, thoroughly flush the system again, and see if it comes back. If it does, it's probably time to pull the slave and send it to BBi for inspection and rebuild if necessary.

* I get what you're saying that anything rated for the CHF 11S should be fine for brake fluid, but whatever the problem I'm having is it doesn't seem to make sense, so that hose being the culprit still seems like something worth eliminating. I do agree that it appears the real problem is pentosin contamination from somewhere though.

 

Update:

I swapped out my reservoir hose and gave the system a thorough bleed today. Clutch feel improved markedly: less pressure required to actuate, and gear changes felt smoother too, which was a surprise.

Here's the hose I used for the reservoir; fits great: (I understand that the stock hose should be able to withstand DOT4 fine, and maybe it was just the pentosin contamination that killed it, but I figure I'll be safe and use a hose designed for DOT4.)

Anyway, I vacuumed out the reservoir with a turkey baster type thing, then removed it and the hose and cleaned it out thoroughly. Replaced it with a length of this braided hose, then thoroughly flushed the system using a Motive pressure bleeder (Euro black label). Put about 2L of fluid through it, including pumping the clutch several times to flush out the master.

Hopefully that'll do it! Planning to check back regularly to see if I get any more hose bits or white scum (apparently from pentosin/dot4 mxing) accumulating in the reservoir, as well as being attentive for worsening in clutch feel.

 

Thanks for the update!

 

always a good idea to change the clutch master as well