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Discussion Starter · #1 ·
I've got a 2008 v6 coupe. Its previous owner(s) did almost no maintenance in its 140k miles, the details don't matter but its not been great.

It does weird stuff if you shift over 5k rpms or hold in the clutch for more than 30 seconds. Shifting over 5k rpms is the part that actually bothers me, its no problem to just put it in neutral and let the clutch out if I'm going to do more than change gears. If I try to shift over 5k rpms, the downstroke feels mostly normal, it looses pressure at the very bottom but the rest is fine. On the way up it will stick to the floor for the first very little bit, it will then feel normal until about half way up when the clutch will fully engage very abruptly. The rest of the stroke has no pressure, it doesn't even push hard enough to lift the weight of my leg. The next 2 - 4 shifts will have similar issues, but it will also feel like you are "un sticking" the clutch from the flywheel on the way down. Its very abrupt and makes shifting smoothly impossible.

I've bled the clutch line, which actually fixed the issue. The fluid was opaque, looked like it had never been changed, there was also air in the line. I replaced it all with new dot 3 brake fluid and it felt perfect for about 2 days/100 miles of rush hour traffic driving. Was able to shift at redline without issue, it felt the same as shifting at 3k. However its back to doing it again. I'd think that never changing the fluid would have damaged the master, slave or both, but I don't know enough and I'm not in a hurry to just start throwing random parts at it.

Any ideas where to start on fixing this? Sorry if this has been covered somewhere, I looked around but couldn't find anything.
 

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If there was air in the line, and no recent service has been done, there is a leak. Likely the clutch master pulling a tiny amount of air through worn seals or bad diaphragm, every time you let the pedal up.

Was the fluid opaque whiteish or brown/black? Whiteish suggests water contamination (dot 3 is made to mix with water) dark fluid is dirt/solids.

The factory slave cylinder has a delay(check) valve. Fluid travels as expected when the pedal is pressed down but when you let the pedal up the valve closes and the fluid is forced through a much smaller passage to bypass the valve. Dirty fluid can gunk up the valve and the passage making fluid return even slower.

There is a diaphragm in the master that works with the delay valve(if it wasn't there, the pedal would return much more slowly, inline with the rate that the fluid is actually leaving the slave. The diaphragm can fail and will lead to issues with the delay system and air to be drawn into the master.
 

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Discussion Starter · #3 ·
Was the fluid opaque whiteish or brown/black? Whiteish suggests water contamination (dot 3 is made to mix with water) dark fluid is dirt/solids.
The fluid was brown. I have no doubt that no service was done to this car in at least 50k miles. I've ordered new master and slave cylinders, I can't see what else it could be. The clutch itself feels great, never slips and engages smoothly when the hydraulics work correctly. I'll update this thread just for posterity after I get them and put them in.
 

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Yea I modded my car again
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When I got my car the first thing I did was replace the slave (at the fire wall attached to the pedal). That got the car shifting perfectly.

I then years later had it clicking for whatever reason so I replaced it again, and this time I had the master cylinder replaced at the transmission itself.

If I were you I would do both like I did, I would replace the line going from the slave to the master as well. You could go all oem, but it might be easier to go with the p2r clutch line as it's flexible and steel braided so it will increase the feel and accuracy of the clutch engagement.

I have a p2r steel line (goes in place of the rubber flex line) and it made the clutch feel more accurate.

You could also do the slave modification if you buy a new one and that should help increase the accuracy of the clutch engagement also.
 

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When I got my car the first thing I did was replace the slave (at the fire wall attached to the pedal). That got the car shifting perfectly.

I then years later had it clicking for whatever reason so I replaced it again, and this time I had the master cylinder replaced at the transmission itself.
Not trying to be difficult, but you have those reversed. Master cylinder is at the firewall, attached to the pedal. Slave is at the transmission, actuating the clutch fork.

If a person was buying both anyway, with plans to delete the delay valve, it makes sense to purchase a master that lacks the diaphragm as well.
 

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Yea I modded my car again
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Good catch yes my bad. Did the ol switcharoo
 

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Discussion Starter · #7 ·
I got it all in with great difficulty last weekend. New master without the diaphragm, new slave with the check valve removed and a new complete line. I had initially planned to use the p2r line to replace just the rubber section, but the fittings on the stock hard lines were so corroded that I couldn't re use them. Only option I could make happen fast enough to drive it to work the next day was a complete braided steel line from master to slave. Its all working properly, feels the same to shift at redline as it does shifting at 3k. Only issue(?) now is the vibration through the clutch pedal. I can very distinctly feel the engine through the clutch for its full travel. The vibration changes depending on what rpms I'm at. I'm not sure if this is from the steel line, or if it should be expected after getting rid of all the factory damping in the clutch system. If thats just how it is I dont really mind, but if it isn't supposed to feel like that I'd like to do something about it.
 

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It is likely from removing the damping in the stock clutch system but could also be caused by a small amount of trapped air. Not sure what effect the braided line would have since it is running end to end.
 

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What you are likely experiencing is a separate issue that is probably clutch/bearing related.

I had this happen to me off of a freshly installed clutch and flywheel, with new master cylinder and slave. The vibration was actually at the lever coming off the transmission. Now that everything is new you replaced and you are getting proper movement of the clutch pedal, those vibrations at the transmission go back up through the hydraulic line and resonate through the pedal. In your case your clutch is worn out from old age or because of how sloppy it was engaging for so long. I could actually see visually the metal lever at the transmission ever so slightly move. That lever rests on the slave and then it travelled back up to the clutch.

For me, if I put the slightest pressure on the clutch it would go away.

With the car on in N, you should be able to put your hand by the clutch slave (at the transmission) it rest on a little bar. Likely the vibration is right there.

If that's the case, For me I just let it happen for 5-10K miles and it went away. I would drive the car as normal and see if it gets better. Somehow it did for me so.... its worth waiting I think to see how things go after a bit of time.
 

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Discussion Starter · #10 ·
I was reading a bit about it and most people suggested it's the actual clutch and not something I did. I can feel slight vibration on the fork. I can also feel slight vibration on the whole motor/trans so idk. My engine mounts could probably stand to be replaced. Either way, your probably right about it being something in the actual clutch.

I'm glad yours fixed itself, I've never done a clutch before and this is my only car atm. I'd rather not attempt something of that scale when I need to drive it to work on Monday. The car has 140k miles on it and I've got no idea how good it's previous owner was. It never slips but the disk might be warped or it might have a bad throwout bearing.

For now I'll let it be and see if it improves, it's something I can worry about later.
 

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A throw out bearing that is starting to go will typically cause some vibration and or noise when the pedal is fully released. It is often most noticeable with the pedal out and the transmission in neutral. Putting very slight pressure on the pedal to push the bearing into the pressure plate fingers will often make the noise and vibration go away.
Also if the master cylinder isn't properly adjusted it can cause the throw out to preload the pressure plate, which could lead to some vibration and will damage the clutch and bearing over time.
 
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