Unusual clutch behavior after RV6 retrofit kit install

[Dan_E26]

Hey all,

About a month ago I had the RV6 FK8 retrofit kit put in my car by a shop. Things were normal for a time but after the break-in I've noticed a few things:

1. (The biggest thing) Occasionally the bite point seems to move around and the amount of effort it takes to actually depress the clutch changes. This often happens after a long stint on the highway and the symptoms include a significantly heavier pedal feel and a higher bite point, closer to the top of the travel. The default state of the clutch is slightly higher pedal effort than stock with a bite point that begins maybe an inch off the floor. When this problem starts to arise, the pedal effort becomes tractor-like and the bite point is nearly right at the top. I don't know what's causing this other than potentially some air in the lines. The fluid level is nominal, and I haven't bled the clutch yet, but if there were air in the system, why does the problem seem to only make itself known after an extended drive?

2. (minor thing) A clutch pedal is supposed to have a bit of a dead zone before the pressure plate actually starts to move, right? I notice there is basically no "dead zone" at the top of the pedal travel where there is little to no pedal effort. It's basically the same effort through the entire pedal swing. I tried adjusting the clutch adjustment screw under the dashboard, thinking that maybe the shop just set the pedal a bit too low and was pre-loading the clutch, but even after pulling it back quite a bit there is no change in the pedal behavior. Do I have to adjust the master cylinder directly? Obviously, you don't want a situation where the pedal adjustment is essentially making a mechanical "riding the clutch" situation, but as far as I can tell, the clutch is fully locked up when my foot is off the pedal. Several pulls in 4th gear on maps 2 and 3 have confirmed this.

Can anybody offer any suggestion on what to do here? I don't really care too much about the lack of a dead zone at the top of the pedal swing (if anything, I appreciate the consistency) but the bipolar pedal feel is bizarre and, frankly, unpleasant to drive.

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[Stanleywinthrop]

I would bleed the clutch, as the most likely explanation is air in the system. Air volume is very responsive to temperature change so that could explain why you experience symptoms at certain times and not others. After that, adjust the clutch pedal. I'm betting these two things will fix your problem.

 

[axion_industries]

i would try doing all the things that are free first. Bleed the clutch, you can also just the pedal adjustment under the dash which helps. We always recommend to ditch the stock soft clutch line with a stainless braided line, its a big difference for little money.

 

[Dan_E26]

Unfortunately, literally right after I made this post, I went out to my car and noticed some brake fluid dripping onto my floor mats. The CMC is leaking

I am gonna call the shop who did my clutch and see if they'll make good on this, otherwise I'll be replacing it myself. Such is the modified car life, I guess.

 

[axion_industries]

Unfortunately, literally right after I made this post, I went out to my car and noticed some brake fluid dripping onto my floor mats. The CMC is leaking

I am gonna call the shop who did my clutch and see if they'll make good on this, otherwise I'll be replacing it myself. Such is the modified car life, I guess.

Let me know, we have the CMC in stock

 

[Dan_E26]

Let me know, we have the CMC in stock

I'm assuming you're referring to the clutch masters kit rather than OEM, right?

If so, do you know if the kit comes with any literature for setting the adjustments, or am I on my own there?

 

[axion_industries]

I'm assuming you're referring to the clutch masters kit rather than OEM, right?

If so, do you know if the kit comes with any literature for setting the adjustments, or am I on my own there?

it doesnt you just have to adjust yourself, I have several people running it but you do have to mod the arm to the clutch pedal but its very straight forward

 

[Dan_E26]

Brief update to this: I replaced the leaking CMC with a replacement OEM one and bled it using a pressure bleeder. I just put the thing straight in there out of the box with no adjustments, and it feels pretty decent already. If I'm gonna complain about anything, the clutch grabs a little low. Maybe a bit too much free play at the top, now! That's pretty easy to adjust, though. Loosen the pedal position screw by a half turn or so, and extend the CMC rod by about the same until there's just a liiiiittle bit of free play.

Regarding the install, I was kinda worried about bleeding the CMC, since it uses the brake reservoir rather than its own independent one, and the output from the CMC is a hard line with an O-Ring connector. There's really no way to bench bleed a CMC like that! It ended up working out, I think. I used a pressure bleeding system that enabled me to just crack the CSC bleeder valve open and go jiggle the pedal in and out by hand while the pressure pump provided more fluid. I kept at that until the big bubbles were gone, then just let it bleed on its own until I stopped seeing air come down the drain line. It's actually kinda amazing how much different the pedal feels now that it's properly bled. The RV6 CTR clutch really isn't much heavier than the factory SI clutch. Before I did this, there must have been a ton of air in the lines that would expand and make the pedal super stiff once it got hot.

I'll probably put this in the tuned reliability thread too, since I may be one of the first 11th-gen folks out there to need a new CMC.

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