Several months back I was due for a clutch replacement, so I took the opportunity to upgrade to a "Sachs 2.5" kit from Sam @ ByDesign, as well as the BBI slave cylinder conversion to bypass the power steering assist. The new clutch felt great - firm, but much more consistent than before.

Unfortunately, when I took the car out for a track day a couple weeks later, I started having problems with clutch hydraulics immediately afterward. (As soon as the car had sat for a while and cooled down, the pedal went to the floor with no resistance and stayed like that for a couple days. Eventually it partially recovered, but still didn't feel normal.) The shop investigated and found that all the clutch hydraulic lines were "swollen". They spoke with BBI, who said the only explanation is the wrong fluid was used; it should be DOT4. They DID use DOT 4 when it was installed, but just in case, the shop replaced all the lines, flushed out all the fluid, and replaced with new DOT 4. Afterward, things seemed back to normal initially, until I pushed the car again. This time it was only an autocross, so barely anything really, but still got similar symptoms afterward, and the shop again found that all the (new) lines had swelled.

BBI says there's no way that could happen with the proper fluid, except.. obviously it did happen. All the shop can recommend now is to put the stock slave cylinder back in, replace the lines again, and see if happens again. Unfortunately I probably won't know until I have a chance to take the car to the track again, and I'm not sure when that will be with winter coming.

For now, I wanted to see if anyone had any idea what could cause this besides the wrong fluid (whether relating to the aftermarket slave or not). It seems likely it's related, but obviously I want to withhold judgement until I've had a chance to track the car with the stock slave back in place. Lines swelling would seem to be caused by either chemical breakdown of some kind, or heat expansion - but obviously these cars are designed to be taken to the track, and a 45 second autocross run (or a few of them over the course of a day) barely pushes the car at all, so it seems like there must be more to it. Plus obviously others who've used this part have tracked the car without these issues. I just don't know enough about the system to have any idea what it could be. (And the Porsche mechanics and folks at BBI also appear to be stumped unfortunately.)

 

You got a pretty odd case on your hands. Do you happen to have pictures of the swollen hoses?

The only way I can see this happening is if the wrong fluid was used. Was it actually Porsche Dot 4 or generic dot 4? There should not be a difference anyways but i don't know what else there is to try.

 

It was a Porsche dealership, and after it happened the first time they double-checked with BBI that they're using the correct fluid. I'll get them to send me a picture of one of the containers. They also said that they flushed over a gallon of it through to be 100% certain all old fluid was gone before refilling after the first time this happened. So I can't imagine how it could be the wrong fluid. (Unless there are, like, different kinds of DOT 4 for brakes and clutch or something, but as far as I can tell, it's all the same...)

 

My BBI slave crapped out on me a few months ago .... if they don't remove all the old fluid before putting in the correct stuff the seals will blow and no clutch pedal ...

bet it needs a rebuilt

 

That doesn't explain why the clutch lines swelled up though, does it? Also, after the first time it happened and all the lines were replaced, it went back to behaving normally again until this autocross.

 

I can only tell you that the Dot 4 or typically off the shelf fluid works with after market seals, probably viton, and Pentosin the Porsche fluid will destroy the standard off the shelf stuff such as Tilton hydrualics which is top of the park as far as sealing materials.

regards

 

There's no evidence of a problem with the seals though (unless that could somehow result in the lines being over pressurized.) Could dot 4 fluid cause the hydraulic lines to break down? Or if not, how could they be getting over pressurized? Could a defective slave do that?

 

Sorry to hear about your problem!I was thinking about installing the BBI slave but will hold off for now.

 

I was just speaking with the lead tech at the Porsche dealership working on the car. He says it's pretty clear the lines are showing signs of chemical breakdown. Specifically, it's the rubber hose that runs from the reservoir to the master, as well as the one that runs from that system to the slave. (All the other lines are solid.) We looked into it and found that the GT2, which uses DOT4, has different part numbers for both of these lines. (The first is a solid plastic line because it connects to the brake reservoir, but the flexible hose that connects to the slave is a different part number as well, suggesting that the Turbo hoses aren't designed for DOT 4.) He's convinced the problem is that these parts (including the seals in the master cylinder, which also has a different part number for the GT2) aren't designed for DOT 4 fluid, and that's why they're breaking down.

Of course, that doesn't explain why everyone who's done this mod isn't experiencing the same thing. The only explanation I can come up with is that it has only happened when I've pushed the car - first at a track day, and second at an autocross. Most people don't track their cars, so might not have run into this.

Sent this info to BBI to see what they say. I'm also looking into whether these lines are replaced when people do the GT2 conversion, since it also involves switching to DOT 4.

 

Interesting...keep us updated.

 

Interested as well. BBI has installed their slave cylinder on my 09 MT Turbo. Although my car is still at the shop and hasn’t been driven since the install.

 

I spoke with Sam Stone at EVOMS, which sells the GT2 conversion kit. Found that they do replace one of the hydraulic lines, but only because the connection to the GT2 slave is different, and they don't replace the other one. He said DOT 4 is generally much easier on components than the Pentosin fluid, so it shouldn't be causing this.

What I do know is that the Pentosin site warns not to mix their CHf 11s with DOT4, or it WILL cause breakdown of lines. I can't see how there could be any of it still in the system though, since the lines have been replaced and the whole system has been flushed *twice*.

The only other thing I can think of is, the power steering fluid (Pentosin CHf202 I think?) also apparently breaks down rubber lines. Maybe something is broken in the BBI slave and it's allowing some power steering fluid into the clutch lines? Seems.. unlikely, but it's the only remotely plausible thing I can come up with at the moment.

I would be interested to hear from anyone who has a BBI slave and has tracked their car, to rule out a common issue!

 

I tracked my car,,,, pedal fell to the floor after a track day,,, just made it home and when we pulled the slave and sent it to BBI they said there was some incorrect fluid in the system and that the lines were probably not flushed correctly ...

cant help with the bulging lines - but the pedal drop is identical issue as I experienced ...

 

Interesting! Is it possible the lines were swelled and your mechanic didn't notice? The guys here didn't notice it the first time I had it in; they just tried bleeding the system, which put it back to.. close to normal for a bit, until it ultimately came back. Wasn't until they looked closer that they noticed.

Certainly is interesting that you got exactly the same symptom, also with a BBI slave. Has anyone else here installed the part and tracked their car?

 

Sorry to hear that. Unfortunately that's the beauty of aftermarket stuff, it rarely works as well as the OEM parts. Seen it a million times. My suggestion would be to cut your losses. Drill and tap the gearbox as is done at the factory and install all the correct GT2 parts. It's a simple half day's work for a competent mechanic. Doing it the OEM way just works plain and simple, doesn't detract from the value of the car, and in the long run comes out cheaper since you don't have to screw around for hours trying to figure out why it's not working properly. Good luck...